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Polymers, Volume 14, Issue 8 (April-2 2022) – 138 articles

Cover Story (view full-size image): The attractive properties of poly(L-lactic acid) (PLA) and its aliphatic polyesters [poly(ethylene adipate) (PEAd) and poly(butylene adipate) (PBAd)] render them ideal co-formulants for the preparation of modified release pharmaceutical formulations. In this report, the in vitro modified release of the chronobiotic hormone melatonin (MLT) from PLA and the aforementioned copolymer matrix tablets is reported. It was found that, depending on the composition and the relevant content of these excipients in the matrix tablets, the release of MLT satisfied the sought targets for fast sleep onset and sleep maintenance. View this paper.
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16 pages, 17581 KiB  
Article
Improved Mechanical Properties and Bioactivity of Silicate Based Bioceramics Reinforced Poly(ether-ether-ketone) Nanocomposites for Prosthetic Dental Implantology
by Noha Taymour, Amal E. Fahmy, Mohamed Abdel Hady Gepreel, Sherif Kandil and Ahmed Abd El-Fattah
Polymers 2022, 14(8), 1632; https://doi.org/10.3390/polym14081632 - 18 Apr 2022
Cited by 20 | Viewed by 3411
Abstract
Polyether-ether-ketone (PEEK) biomaterial has been increasingly employed for orthopedic, trauma, spinal, and dental implants due to its biocompatibility and in vivo stability. However, a lack of bioactivity and binding ability to natural bone tissue has significantly limited PEEK for many challenging dental implant [...] Read more.
Polyether-ether-ketone (PEEK) biomaterial has been increasingly employed for orthopedic, trauma, spinal, and dental implants due to its biocompatibility and in vivo stability. However, a lack of bioactivity and binding ability to natural bone tissue has significantly limited PEEK for many challenging dental implant applications. In this work, nanocomposites based on PEEK reinforced with bioactive silicate-based bioceramics (forsterite or bioglass) as nanofillers were prepared using high energy ball milling followed by melt blending and compression molding. The influence of nanofillers type and content (10, 20 and 30 wt.%) on the crystalline structure, morphology, surface roughness, hydrophilicity, microhardness, elastic compression modulus, and flexural strength of the nanocomposites was investigated. The scanning electron microscopy images of the nanocomposites with low nanofillers content showed a homogenous surface with uniform dispersion within the PEEK matrix with no agglomerates. All nanocomposites showed an increased surface roughness compared to pristine PEEK. It was found that the incorporation of 20 wt.% forsterite was the most effective in the nanocomposite formulation compared with bioglass-based nanocomposites; it has significantly improved the elastic modulus, flexural strength, and microhardness. In vitro bioactivity evaluation, which used biomimetic simulated body fluid indicated the ability of PEEK nanocomposites loaded with forsterite or bioglass nanofillers to precipitate calcium and phosphate bone minerals on its surface. These nanocomposites are expected to be used in long-term load-bearing implant applications and could be recommended as a promising alternative to titanium and zirconia when used as a dental implant material. Full article
(This article belongs to the Special Issue Advanced Polymeric Composites in Dentistry: Synthesis, Properties, and Applications)
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Figure 1
<p>XRD patterns showing the effect of adding BG and FT nanoparticles on the crystallinity of PEEK: (<b>a</b>) nanocomposites filled with BG nanoparticles and (<b>b</b>) nanocomposites filled with FT nanoparticles.</p> Full article ">Figure 2
<p>SEM micrographs of the surface morphologies showing details of smooth and rough regions for pure PEEK and PEEK nanocomposites loaded with different content (10, 20, 30 wt.%) of BG and FT nanofillers: (<b>a</b>) smooth PEEK, (<b>b</b>,<b>c</b>) rough PKBG-10 and PKBG-20, (<b>d</b>) rough agglomeration of BG nanoparticles on PKBG-30, (<b>e</b>) smooth PKFT-10, and (<b>f</b>,<b>g</b>) low rough PKFT-20 and PKFT-30 with randomly distributed FT nanoparticles within the PEEK matrix.</p> Full article ">Figure 3
<p>Variations of microhardness (mean ± SD) of the PEEK nanocomposites as a function of the nanofillers content. (<span class="html-italic">n</span> = 6, <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 4
<p>Variations of elastic compression elastic modulus (mean ± SD) of the PEEK-based nanocomposites as a function of BG and FT content. (<span class="html-italic">n</span> = 6, <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 5
<p>Variations of flexural strength (mean ± SD) of the PEEK/nanocomposites as a function of the nanofillers content. (<span class="html-italic">n</span> = 6, <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 6
<p>SEM micrographs showing the apatite-formation ability of the pure PEEK and PEEK nanocomposites after immersion in SBF for 7, 14, and 28 days: (<b>a1</b>–<b>a3</b>) pure PEEK, (<b>b1</b>–<b>b3</b>) PKBG-20 and (<b>c1</b>–<b>c3</b>) PKFT-20. No changes were observed on the surface of pure PEEK (<b>a1</b>–<b>a3</b>) but the PEEK nanocomposites (<b>b1</b>–<b>b3</b>,<b>c1–c3</b>) induced apatite formation after immersion in SBF for all time intervals.</p> Full article ">
28 pages, 18210 KiB  
Article
A Comparison of Numerical and Actual Measurements of Large-Scale Rib-Structured Pallet Flatness Using Recycled Polypropylene in Injection Molding
by Yi-Ling Liao and Hsi-Hsun Tsai
Polymers 2022, 14(8), 1631; https://doi.org/10.3390/polym14081631 - 18 Apr 2022
Cited by 2 | Viewed by 2166
Abstract
Many challenges are associated with the injection molding process for forming a rib-structured pallet (1100 mm × 1100 mm × 140 mm, length × width × height) because greater flowing resistance through the rib channels within the pallet can induce insufficient filling. Essentially, [...] Read more.
Many challenges are associated with the injection molding process for forming a rib-structured pallet (1100 mm × 1100 mm × 140 mm, length × width × height) because greater flowing resistance through the rib channels within the pallet can induce insufficient filling. Essentially, multi-gate filling involves a sequential valve gate system, which helps to spread the filling front with fewer weld lines. Based on the presetting of the sequential scheme of the valve gates, actual measurements of pallet flatness using the ATOS scan system were compared to numerical warpage measurements of a pallet derived by Moldex3D 2020. In this study, we propose a sequential scheme by actuating the valve gates to open once the flow front spreads towards them; then, actual warpage measurements of a pallet are compared with numerical measurements. The results show that the warpage of the top surface of the pallet is 5.144 mm in actual measurements and 5.729 mm in simulation. The results all indicated small warpage with respect to the pallet size. The simulation and actual measurements of flatness are in excellent agreement; the difference in top flatness between the simulated and actual pallet is 0.59 mm, while the bottom flatness difference is 0.035 mm. By adjusting the cooling water temperature, increasing the mold temperature, and decreasing the material temperature, overall flatness and warpage displacement can be reduced. Full article
(This article belongs to the Special Issue In-Situ Polymer Characterization in Polymer Processing)
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Figure 1
<p>Injection-molded pallet (1100 mm × 1100 mm × 140 mm): (<b>a</b>) isometric view of the pallet (top side); (<b>b</b>) isometric view of the pallet (bottom side); (<b>c</b>) isometric view of the baffle cooling flow system on the top side of the pallet; (<b>d</b>) isometric view of the baffle cooling flow system on the bottom side of the pallet; (<b>e</b>) 12 filling gates in the pallet.</p> Full article ">Figure 1 Cont.
<p>Injection-molded pallet (1100 mm × 1100 mm × 140 mm): (<b>a</b>) isometric view of the pallet (top side); (<b>b</b>) isometric view of the pallet (bottom side); (<b>c</b>) isometric view of the baffle cooling flow system on the top side of the pallet; (<b>d</b>) isometric view of the baffle cooling flow system on the bottom side of the pallet; (<b>e</b>) 12 filling gates in the pallet.</p> Full article ">Figure 1 Cont.
<p>Injection-molded pallet (1100 mm × 1100 mm × 140 mm): (<b>a</b>) isometric view of the pallet (top side); (<b>b</b>) isometric view of the pallet (bottom side); (<b>c</b>) isometric view of the baffle cooling flow system on the top side of the pallet; (<b>d</b>) isometric view of the baffle cooling flow system on the bottom side of the pallet; (<b>e</b>) 12 filling gates in the pallet.</p> Full article ">Figure 2
<p>Properties of recycled PP: (<b>a</b>) relative crystallinity with respect to shear rate and cooling rate; (<b>b</b>) constant pressure heat capacity with respect to temperature; (<b>c</b>) thermal conductivity with respect to temperature; (<b>d</b>) viscosity with respect to temperature; (<b>e</b>) pressure–volume–temperature relationships.</p> Full article ">Figure 2 Cont.
<p>Properties of recycled PP: (<b>a</b>) relative crystallinity with respect to shear rate and cooling rate; (<b>b</b>) constant pressure heat capacity with respect to temperature; (<b>c</b>) thermal conductivity with respect to temperature; (<b>d</b>) viscosity with respect to temperature; (<b>e</b>) pressure–volume–temperature relationships.</p> Full article ">Figure 2 Cont.
<p>Properties of recycled PP: (<b>a</b>) relative crystallinity with respect to shear rate and cooling rate; (<b>b</b>) constant pressure heat capacity with respect to temperature; (<b>c</b>) thermal conductivity with respect to temperature; (<b>d</b>) viscosity with respect to temperature; (<b>e</b>) pressure–volume–temperature relationships.</p> Full article ">Figure 3
<p>Comparisons of the experimental and numerical flow fronts in short-shot testing under the preset sequential valve gate scheme: (<b>a</b>) 57.9% short-shot true pallet; (<b>b</b>) 57.9% numerical flow front of short-shot testing; (<b>c</b>) 74.4% short-shot true pallet; (<b>d</b>) 74.4% numerical flow front of short-shot testing.</p> Full article ">Figure 3 Cont.
<p>Comparisons of the experimental and numerical flow fronts in short-shot testing under the preset sequential valve gate scheme: (<b>a</b>) 57.9% short-shot true pallet; (<b>b</b>) 57.9% numerical flow front of short-shot testing; (<b>c</b>) 74.4% short-shot true pallet; (<b>d</b>) 74.4% numerical flow front of short-shot testing.</p> Full article ">Figure 4
<p>Flatness of the pallet when adjusting the mold temperature.</p> Full article ">Figure 5
<p>Influence on flatness values by adjusting the melt temperature.</p> Full article ">Figure 6
<p>Influence on flatness values by adjusting the cooling water temperatures.</p> Full article ">Figure 7
<p>Influence on flatness by adjusting the cooling time.</p> Full article ">Figure 8
<p>Influence on flatness when lengthening the packing time and shortening the cooling time.</p> Full article ">Figure 9
<p>(<b>a</b>) Changes in the top height of the pallet measured by the ATOS system (flatness 5.144 mm); (<b>b</b>) changes in the top height of the pallet under the time control of 40 s of packing time (flatness 5.729 mm).</p> Full article ">Figure 9 Cont.
<p>(<b>a</b>) Changes in the top height of the pallet measured by the ATOS system (flatness 5.144 mm); (<b>b</b>) changes in the top height of the pallet under the time control of 40 s of packing time (flatness 5.729 mm).</p> Full article ">Figure 10
<p>(<b>a</b>) Flow front spreading to hit gates 5 and 9 at 4.35 s; (<b>b</b>) Flow front spreading to hit gate 8 at 4.67 s; (<b>c</b>) Flow front spreading to hit gates 6, 7, 11, and 129 at 10.8 s.</p> Full article ">Figure 10 Cont.
<p>(<b>a</b>) Flow front spreading to hit gates 5 and 9 at 4.35 s; (<b>b</b>) Flow front spreading to hit gate 8 at 4.67 s; (<b>c</b>) Flow front spreading to hit gates 6, 7, 11, and 129 at 10.8 s.</p> Full article ">Figure 11
<p>(<b>a</b>) Measured point for the top height of the pallet in the x-axis direction; (<b>b</b>) measured point for the top height of the pallet in the y-axis direction; (<b>c</b>) comparison between the simulated and actual top height profiles of the pallet in the x-axis direction; (<b>d</b>) comparison between the simulated and actual top height profiles of the pallet in the y-axis direction.</p> Full article ">Figure 11 Cont.
<p>(<b>a</b>) Measured point for the top height of the pallet in the x-axis direction; (<b>b</b>) measured point for the top height of the pallet in the y-axis direction; (<b>c</b>) comparison between the simulated and actual top height profiles of the pallet in the x-axis direction; (<b>d</b>) comparison between the simulated and actual top height profiles of the pallet in the y-axis direction.</p> Full article ">Figure 11 Cont.
<p>(<b>a</b>) Measured point for the top height of the pallet in the x-axis direction; (<b>b</b>) measured point for the top height of the pallet in the y-axis direction; (<b>c</b>) comparison between the simulated and actual top height profiles of the pallet in the x-axis direction; (<b>d</b>) comparison between the simulated and actual top height profiles of the pallet in the y-axis direction.</p> Full article ">Figure 12
<p>(<b>a</b>) The actual height profile change of the bottom side of the pallet measured by the ATOS system (flatness 6.385 mm); (<b>b</b>) simulated changes of the bottom height profile of the pallet during a packing time of 40 s by time control.</p> Full article ">Figure 13
<p>(<b>a</b>) Bottom side height profile measurement points in the x-axis direction of the pallet; (<b>b</b>) bottom side height profile measurement points in the y-axis direction of the pallet; (<b>c</b>) comparison of the simulated and actual heights of the bottom central part of the pallet in the x-axis direction; (<b>d</b>) comparison of the simulated and actual bottom side height profiles of both sides of the pallet in the x-axis direction.</p> Full article ">Figure 13 Cont.
<p>(<b>a</b>) Bottom side height profile measurement points in the x-axis direction of the pallet; (<b>b</b>) bottom side height profile measurement points in the y-axis direction of the pallet; (<b>c</b>) comparison of the simulated and actual heights of the bottom central part of the pallet in the x-axis direction; (<b>d</b>) comparison of the simulated and actual bottom side height profiles of both sides of the pallet in the x-axis direction.</p> Full article ">
15 pages, 5240 KiB  
Article
Facile Preparation of Cellulose Fiber Reinforced Polypropylene Using Hybrid Filler Method
by Safarul Mustapha, Jacqueline Lease, Kubra Eksiler, Siew Teng Sim, Hidayah Ariffin and Yoshito Andou
Polymers 2022, 14(8), 1630; https://doi.org/10.3390/polym14081630 - 18 Apr 2022
Cited by 6 | Viewed by 3764
Abstract
Dried hybrid fillers comprised of silica/CNF were successfully synthesized in ethanol/water mixed solvents at room temperature without the usage of any precursor. The as-prepared fillers were incorporated with polypropylene (PP) as a polymer matrix through a twin-screw extruder. From surface morphology analysis, the [...] Read more.
Dried hybrid fillers comprised of silica/CNF were successfully synthesized in ethanol/water mixed solvents at room temperature without the usage of any precursor. The as-prepared fillers were incorporated with polypropylene (PP) as a polymer matrix through a twin-screw extruder. From surface morphology analysis, the agglomeration of the silica/CNF hybrid fillers was prevented in the PP matrix and they exhibited moderate transparency, around 17.9% and 44.6% T at 660 nm. Further, the chemical structures of the polymer composites were identified by Fourier transform infrared (FT-IR) analysis. According to thermogravimetric analysis (TGA), the insertion of silica as a co-filler to the PP matrix resulted in an increase in its degradation onset temperature and also thermal stability. In addition, the mechanical properties of the PP composites also increased after the blending process with the hybrid fillers. Overall, sample PP-SS/CNF exhibited the highest tensile strength, which was 36.8 MPa, or around 73.55% compared to the pristine PP. The improvements in tensile strength were attributed to good dispersion and enhanced efficiency of the stress transfer mechanism between the silica and the cellulose within the PP matrix. However, elongation of the sample was reduced sharply due to the stiffening effect of the filler. Full article
(This article belongs to the Special Issue Advances in the Processing and Application of Polymer and Its Composites)
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Figure 1
<p>Interaction of fine particles and CNFs in ethanol/water mixed solvent.</p> Full article ">Figure 2
<p>Images of SiP/CNF filler; (<b>a</b>) hybrid filler preparation, (<b>b</b>) agglomerated CNFs without SiPs and (<b>c</b>) hybrid filler mechanism in PP polymer.</p> Full article ">Figure 3
<p>Morphological image of SiP particles: (<b>a</b>) SiP SS 50X, (<b>b</b>) SS/CNF 1000X, (<b>c</b>) SiP SP 50X, and SEM image of hybrid filler, (<b>d</b>) SP/CNF 1000X.</p> Full article ">Figure 4
<p>Digital images showing the transparency of (<b>a</b>) PP, (<b>b</b>) PP-8.75 SS, (<b>c</b>) PP-8.75 SP, (<b>d</b>) PP-1.25 CNF, (<b>e</b>) PP-SS/CNF, and (<b>f</b>) PP-SP/CNF.</p> Full article ">Figure 5
<p>UV–vis transmittance spectra for PP and PP composite.</p> Full article ">Figure 6
<p>FTIR spectra of SiP Sylosphere 200, Sylophobic 200, CNF, and PP composites.</p> Full article ">Figure 7
<p>Mechanical properties of (<b>a</b>) stress-strain curves of PP composites and (<b>b</b>) an enlarged graph.</p> Full article ">Figure 8
<p>Mechanical properties of PP composites: bar charts of elongation at break and yield strength.</p> Full article ">Figure 9
<p>SEM images mapped with EDS analysis for distribution of oxygen (O) element represents CNF and silica (Si) element represent SiP: (<b>a</b>) PP polymer, (<b>b</b>) PP-1.25 CNF, (<b>c</b>) PP SS/CNF and (<b>d</b>) PP SP/CNF.</p> Full article ">Figure 10
<p>TGA curves of PP, SiP, CNF, PP SS/CNF, and PP SP/CNF.</p> Full article ">Figure 11
<p>DTA curves of (<b>a</b>) PP SS/CNF, and (<b>b</b>) PP SP/CNF.</p> Full article ">
21 pages, 13508 KiB  
Review
Application of Red Cabbage Anthocyanins as pH-Sensitive Pigments in Smart Food Packaging and Sensors
by Reza Abedi-Firoozjah, Shima Yousefi, Mahshid Heydari, Faezeh Seyedfatehi, Shima Jafarzadeh, Reza Mohammadi, Milad Rouhi and Farhad Garavand
Polymers 2022, 14(8), 1629; https://doi.org/10.3390/polym14081629 - 18 Apr 2022
Cited by 93 | Viewed by 21221
Abstract
Anthocyanins are excellent antioxidant/antimicrobial agents as well as pH-sensitive indicators that provide new prospects to foster innovative smart packaging systems due to their ability to improve food shelf life and detect physicochemical and biological changes in packaged food. Compared with anthocyanins from other [...] Read more.
Anthocyanins are excellent antioxidant/antimicrobial agents as well as pH-sensitive indicators that provide new prospects to foster innovative smart packaging systems due to their ability to improve food shelf life and detect physicochemical and biological changes in packaged food. Compared with anthocyanins from other natural sources, red cabbage anthocyanins (RCAs) are of great interest in food packaging because they represent an acceptable color spectrum over a broad range of pH values. The current review addressed the recent advances in the application of RCAs in smart bio-based food packaging systems and sensors. This review was prepared based on the scientific reports found on Web of Science, Scopus, and Google Scholar from February 2000 to February 2022. The studies showed that the incorporation of RCAs in different biopolymeric films could affect their physical, mechanical, thermal, and structural properties. Moreover, the use of RCAs as colorimetric pH-responsive agents can reliably monitor the qualitative properties of the packaged food products in a real-time assessment. Therefore, the development of smart biodegradable films using RCAs is a promising approach to the prospect of food packaging. Full article
(This article belongs to the Special Issue Biopolymers for Food Packaging Films and Coatings)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Color changes of red cabbage anthocyanin-rich extract at different pH values.</p> Full article ">Figure 2
<p>Color change in a pH-sensitive composite film produced from anthocyanins-loaded PVA–chitosan–gelatin for monitoring the spoilage of ricotta cheese during refrigerated storage: (<b>left</b>) 1 day (<b>right</b>) 7 days [<a href="#B73-polymers-14-01629" class="html-bibr">73</a>].</p> Full article ">Figure 3
<p>Color variation of composite films as exposed to different pH values (2–12) for 10 min. KC: konjac glucomannan films with oxidized chitin nanocrystals without RCA, KCR-3: film with 3% RCA, KCR-6: film with 6% RCA, and KCR-9: film with 9% RCA. Reprinted with permission from Ref. [<a href="#B52-polymers-14-01629" class="html-bibr">52</a>]. Copyright 2019 Elsevier Ltd.</p> Full article ">
15 pages, 3063 KiB  
Article
Green and Rapid Preparation of Fluorosilicone Rubber Foam Materials with Tunable Chemical Resistance for Efficient Oil–Water Separation
by Wan-Jun Hu, Qiao-Qi Xia, Hong-Tao Pan, Hai-Yang Chen, Yong-Xiang Qu, Zuan-Yu Chen, Guo-Dong Zhang, Li Zhao, Li-Xiu Gong, Chang-Guo Xue and Long-Cheng Tang
Polymers 2022, 14(8), 1628; https://doi.org/10.3390/polym14081628 - 18 Apr 2022
Cited by 28 | Viewed by 3714
Abstract
Polydimethylsiloxane (PDMS) foam materials with lightweight, excellent oil resistance and mechanical flexibility are highly needed for various practical applications in aerospace, transportation, and oil/water separation. However, traditional PDMS foam materials usually present poor chemical resistance and easily swell in various solvents, which greatly [...] Read more.
Polydimethylsiloxane (PDMS) foam materials with lightweight, excellent oil resistance and mechanical flexibility are highly needed for various practical applications in aerospace, transportation, and oil/water separation. However, traditional PDMS foam materials usually present poor chemical resistance and easily swell in various solvents, which greatly limits their potential application. Herein, novel fluorosilicone rubber foam (FSiRF) materials with different contents of trifluoropropyl lateral groups were designed and fabricated by a green (no solvents used) and rapid (<10 min foaming process) foaming/crosslinking approach at ambient temperature. Typically, vinyl-terminated poly(dimethyl-co-methyltrifluoropropyl) siloxanes with different fluorine contents of 0–50 mol% were obtained through ring-opening polymerization to effectively adjust the chemical resistance of the FSiRFs. Notably, the optimized FSiRF samples exhibit lightweight (~0.25 g/cm−3), excellent hydrophobicity/oleophilicity (WCA > 120°), reliable mechanical flexibility (complete recovery ability after stretching of 130% strain or compressing of >60%), and improved chemical resistance and structural stability in various solvents, making them promising candidates for efficient and continuous oil–water separation. This work provides an innovative concept to design and prepare advanced fluorosilicone rubber foam materials with excellent chemical resistance for potential oil–water separation application. Full article
(This article belongs to the Section Polymer Chemistry)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Schematic illustration of the fabrication process of FSiRF materials. (<b>b</b>) Optical microscopy image of PDFS-Vi-X/PDMS-H mixture before and during foaming process. (<b>c</b>) Typical image of FSiRF sample on a foxtail grass without bending any hairy branches, indicating a lightweight nature of FSiRF materials. (<b>d</b>) FSiRF materials with a drop of water (blue color) and oil (orange color) on the surface, showing strong oleophilicity and high hydrophobicity of the surface. Digital images of FSiRF materials under (<b>e</b>) a stretching and releasing cycle and (<b>f</b>) a compressing and releasing cycle, showing good reversible stretchability and compressibility.</p> Full article ">Figure 2
<p>(<b>a</b>) Chemical synthesis of PDFS-Vi synthesis process. (<b>b</b>) Schematic illustration of the fabrication process of PDFS-Vi-X with different fluorine contents. (<b>c</b>) <sup>1</sup>H NMR spectra and (<b>d</b>) FTIR spectra of PDFS-Vi-X.</p> Full article ">Figure 3
<p>(<b>a</b>) Crosslinking and (<b>b</b>) foaming process of FSiRF materials at ambient temperature. Structural characterization and analysis of various FSiRF samples. (<b>c</b>) Photographs of (<b>i</b>) pure SiRF, (<b>ii</b>) FSiRF-1, (<b>iii</b>) FSiRF-2, (<b>iv</b>) FSiRF-3, and (<b>v</b>) FSiRF-4. (<b>d</b>) SEM micrographs and (<b>e</b>) pore size distribution of FSiRF materials with different fluorine contents, indicating the pore size increases with the increase in fluorine content.</p> Full article ">Figure 4
<p>Mechanical and thermal properties of FSiRF samples. (<b>a</b>) Compressive stress−strain curves of the FSiRF materials with different fluorine content at strain = 60%, and (<b>b</b>) compression cycle tests at strain = 60% of various FSiRF samples, demonstrating the mechanical stability of the materials. (<b>c</b>) TGA and (<b>d</b>) DTG curves of FSiRF materials under air conditions.</p> Full article ">Figure 5
<p>(<b>a</b>) Swelling process of the FSiRF materials in Hexane and (<b>b</b>) swelling ratios of FSiRF materials for different organic solvents, which shows that the swelling resistance of FSiRF material is enhanced with the increase in fluorine content. (<b>c</b>) Diagram and comparison of the antiswelling mechanism of FSiRF materials with different fluorine contents of 0 and 50%.</p> Full article ">Figure 6
<p>The performance of FSiRF-4 samples in the oil–water separation process. Removal of (<b>a</b>) light organic solvent (xylene dyed by orange) on water surface and (<b>b</b>) heavy organic solvent (dichloromethane dyed by orange) underwater via FSiRF-4 material, demonstrating good absorption capacity. The illustration of continuous oil–water separation performances of FSiRF-4 by plugging it with a pump, pumping (<b>c</b>) light xylene and (<b>d</b>) heavy CH<sub>2</sub>Cl<sub>2</sub> from the oil–water mixture via FSiRF-4 samples. They passed through FSiRF-4 porous samples effectively and quickly, and no water went through the sample owing to the excellent surface hydrophobicity and oleophilicity of the samples.</p> Full article ">
20 pages, 27432 KiB  
Review
Can 3D-Printed Bioactive Glasses Be the Future of Bone Tissue Engineering?
by Amey Dukle, Dhanashree Murugan, Arputharaj Joseph Nathanael, Loganathan Rangasamy and Tae-Hwan Oh
Polymers 2022, 14(8), 1627; https://doi.org/10.3390/polym14081627 - 18 Apr 2022
Cited by 27 | Viewed by 5573
Abstract
According to the Global Burden of Diseases, Injuries, and Risk Factors Study, cases of bone fracture or injury have increased to 33.4% in the past two decades. Bone-related injuries affect both physical and mental health and increase the morbidity rate. Biopolymers, metals, ceramics, [...] Read more.
According to the Global Burden of Diseases, Injuries, and Risk Factors Study, cases of bone fracture or injury have increased to 33.4% in the past two decades. Bone-related injuries affect both physical and mental health and increase the morbidity rate. Biopolymers, metals, ceramics, and various biomaterials have been used to synthesize bone implants. Among these, bioactive glasses are one of the most biomimetic materials for human bones. They provide good mechanical properties, biocompatibility, and osteointegrative properties. Owing to these properties, various composites of bioactive glasses have been FDA-approved for diverse bone-related and other applications. However, bone defects and bone injuries require customized designs and replacements. Thus, the three-dimensional (3D) printing of bioactive glass composites has the potential to provide customized bone implants. This review highlights the bottlenecks in 3D printing bioactive glass and provides an overview of different types of 3D printing methods for bioactive glass. Furthermore, this review discusses synthetic and natural bioactive glass composites. This review aims to provide information on bioactive glass biomaterials and their potential in bone tissue engineering. Full article
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Full article ">Figure 1
<p>Schematic of the apatite formation mechanism in bioactive glass scaffolds.</p> Full article ">Figure 2
<p>Schematic of the sol–gel synthesis of bioactive glass nanoparticles (image adapted from CC BY-SA 3.0 [<a href="#B52-polymers-14-01627" class="html-bibr">52</a>]).</p> Full article ">Figure 3
<p>Additive manufacturing technologies used for the 3D printing of polymer-bioactive glass scaffolds. (Reproduced with permission from [<a href="#B61-polymers-14-01627" class="html-bibr">61</a>,<a href="#B62-polymers-14-01627" class="html-bibr">62</a>] under creative commons CC-BY license) (Reproduced with permission from [<a href="#B63-polymers-14-01627" class="html-bibr">63</a>] Copyright 2020, Elsevier).</p> Full article ">Figure 4
<p>Workflow for different strategies for extrusion-based 3D printing of thermoplastic polymers-bioactive glass scaffolds. (Reproduced with permission from [<a href="#B61-polymers-14-01627" class="html-bibr">61</a>] under creative commons CC-BY license) (Reproduced with permission from [<a href="#B73-polymers-14-01627" class="html-bibr">73</a>] Copyright 2014, Elsevier).</p> Full article ">Figure 5
<p>SEM morphology for PVA-Sr-containing bioactive glass scaffolds before and after 3 days of immersion in SBF: (<b>A1</b>,<b>A2</b>) MBG, (<b>B1</b>,<b>B2</b>) 5Sr-MBG, (<b>C1</b>,<b>C2</b>) 10Sr-MBG, and (<b>D1</b>,<b>D2</b>) 20Sr-MBG. Composition scaffolds before soaking in SBF: (<b>A3</b>,<b>A4</b>) MBG, (<b>B3</b>,<b>B4</b>) 5Sr-MBG, (<b>C3</b>,<b>C4</b>) 10Sr-MBG, and (<b>D3</b>,<b>D4</b>) 20Sr-MBG after soaking in SBF for 3 days. (Reproduced with permission from [<a href="#B73-polymers-14-01627" class="html-bibr">73</a>] Copyright 2014, Elsevier).</p> Full article ">Figure 6
<p>SEM images of hBMSCs attached on (<b>A</b>) MBG/SF and (<b>B</b>) MBG/PCL scaffolds for (<b>A1</b>,<b>B1</b>) 1, (<b>A2</b>,<b>B2</b>) 4, and (<b>A3</b>,<b>B3</b>) 7 days. The red arrows indicate cells. Reproduced from [<a href="#B105-polymers-14-01627" class="html-bibr">105</a>] under copyright CC BY licence.</p> Full article ">Figure 7
<p>SEM morphologies of the robotic-dispensed scaffolds for bone tissue engineering. <b>A</b> (<b>a</b>–<b>c</b>) Chitosan/nanobioactive glass scaffolds and (<b>d</b>,<b>e</b>) Chitosan scaffold at different magnifications. <b>B</b> (<b>a</b>–<b>c</b>) Cells grown on chitosan/nanobioactive glass scaffolds for 3 days at different magnifications d Cell proliferative potential of chitosan and chitosan/nanobioactive glass scaffolds measured by MTS assay Reproduced from [<a href="#B107-polymers-14-01627" class="html-bibr">107</a>] with permission from Copyright 2011, Elsevier.</p> Full article ">Figure 8
<p>The morphology, porosity, and shrinkage of 3D-printed BG/SA composite scaffolds: (<b>a</b>) Top and side-view SEM images of the scaffolds. The BG/SA mass ratios were 0:4, 1:4, 2:4, and 4:4. (<b>b</b>) High- magnification SEM images showing a pore and a vertical section of strands of the BG/SA 2:4 scaffold. (<b>c</b>) Porosity. (<b>d</b>) Scaffold shrinkage (%) in the X, Y, and Z directions. Reproduced from [<a href="#B108-polymers-14-01627" class="html-bibr">108</a>] under copyright CC BY-NC 3.0.</p> Full article ">Figure 9
<p>Cellular morphology of MSCs after treatment with different compositions of bioink. (<b>A</b>) Images representing live/dead cells in each bioink treatment groups at day 1, 3, and 7. (<b>B</b>) Quantitative analysis of the number of live cells. (<b>C</b>) Absorbance value at OD 450 nm in the CCK-8 cell proliferation assay. (<b>D</b>) Hematoxylin and eosin staining images depicting MSC spreading phenomenon. (<b>E</b>,<b>F</b>) Quantitative analysis of cellular extension and cell aspect ratio of extended cells, respectively. Reproduced from [<a href="#B109-polymers-14-01627" class="html-bibr">109</a>] with permission from Copyright 2019, Elsevier).</p> Full article ">
44 pages, 8852 KiB  
Review
Tailoring the Barrier Properties of PLA: A State-of-the-Art Review for Food Packaging Applications
by Stefania Marano, Emiliano Laudadio, Cristina Minnelli and Pierluigi Stipa
Polymers 2022, 14(8), 1626; https://doi.org/10.3390/polym14081626 - 18 Apr 2022
Cited by 85 | Viewed by 11910
Abstract
It is now well recognized that the production of petroleum-based packaging materials has created serious ecological problems for the environment due to their resistance to biodegradation. In this context, substantial research efforts have been made to promote the use of biodegradable films as [...] Read more.
It is now well recognized that the production of petroleum-based packaging materials has created serious ecological problems for the environment due to their resistance to biodegradation. In this context, substantial research efforts have been made to promote the use of biodegradable films as sustainable alternatives to conventionally used packaging materials. Among several biopolymers, poly(lactide) (PLA) has found early application in the food industry thanks to its promising properties and is currently one of the most industrially produced bioplastics. However, more efforts are needed to enhance its performance and expand its applicability in this field, as packaging materials need to meet precise functional requirements such as suitable thermal, mechanical, and gas barrier properties. In particular, improving the mass transfer properties of materials to water vapor, oxygen, and/or carbon dioxide plays a very important role in maintaining food quality and safety, as the rate of typical food degradation reactions (i.e., oxidation, microbial development, and physical reactions) can be greatly reduced. Since most reviews dealing with the properties of PLA have mainly focused on strategies to improve its thermal and mechanical properties, this work aims to review relevant strategies to tailor the barrier properties of PLA-based materials, with the ultimate goal of providing a general guide for the design of PLA-based packaging materials with the desired mass transfer properties. Full article
(This article belongs to the Topic Polymers from Renewable Resources)
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<p>Schematic representation of the general mechanism of the permeation of small molecules through semicrystalline polymers.</p> Full article ">Figure 2
<p>(<b>A</b>) Water vapor permeation estimated fraction of the α form in PLLA films; (<b>B</b>) optical micrographs of compression molded PLLA films after cold crystallization; (<b>C</b>) water vapor permeability of PLLA films crystallized as a function of degree of crystallinity. Adapted from [<a href="#B83-polymers-14-01626" class="html-bibr">83</a>] with permission from Elsevier. Copyright © 2011.</p> Full article ">Figure 3
<p>Schematic representation of the arrangement of crystalline, rigid amorphous and mobile amorphous fractions.</p> Full article ">Figure 4
<p>WAXD patterns of drawn and thermally crystallized PLA films. Adapted from [<a href="#B62-polymers-14-01626" class="html-bibr">62</a>] with permission from American Chemical Society. Copyright © 2012.</p> Full article ">Figure 5
<p>(<b>A</b>) SC crystalline lattice; adapted from [<a href="#B115-polymers-14-01626" class="html-bibr">115</a>] with permission from Elsevier. Copyright© 2016. (<b>B</b>) Optical microscopy micrographs of different PLLA/PDLA films with PLLA content of 75% (<b>a</b>,<b>d</b>), 50% (<b>b</b>,<b>e</b>), and 25% (<b>c</b>,<b>f</b>), crystallized at 200 °C; reproduced from [<a href="#B116-polymers-14-01626" class="html-bibr">116</a>] with permission from American Chemical Society. Copyright © 2010.</p> Full article ">Figure 6
<p>(<b>A</b>,<b>B</b>) POM and cross-sectional micrograph of crystal morphology for PLA with a nucleating agent showing an epitaxial growth lamellae and interlocked structure, respectively; (<b>C</b>) Oxygen permeability coefficient (<span class="html-italic">p</span>) values for all PLA samples as a function of nucleating agent content. Adapted from [<a href="#B125-polymers-14-01626" class="html-bibr">125</a>] with permission from American Chemical Society. Copyright © 2014.</p> Full article ">Figure 7
<p>Example of typical AFM phase images of multilayered film cross-section with on-edge and in-plane orientations. Adapted from [<a href="#B133-polymers-14-01626" class="html-bibr">133</a>] with permission from John Wiley and Sons. Copyright © 2011.</p> Full article ">Figure 8
<p>(<b>A</b>) AFM images of the multilayer film with PLA in light and PBSA in dark; (<b>B</b>) gas permeability and solubility coefficients for the monolayer films of PLA and PBSA and the multilayer film of PLA/PBSA. Adapted from [<a href="#B137-polymers-14-01626" class="html-bibr">137</a>] with permission from American Chemical Society. Copyright © 2017.</p> Full article ">Figure 9
<p>Types of morphology in immiscible polymer blends.</p> Full article ">Figure 10
<p>SEM images of (<b>A</b>) PLA/TPS sheets with CA (including WVP values), adapted from [<a href="#B191-polymers-14-01626" class="html-bibr">191</a>] and (<b>B</b>) fracture surface of neat PHBV, neat PLA, and their blends (including WVP and oxygen permeability values), adapted from [<a href="#B193-polymers-14-01626" class="html-bibr">193</a>] with permission from Elsevier. Copyright © 2013.</p> Full article ">Figure 11
<p>Simplified drawing of the “tortuous path” produced by the incorporation of exfoliated clay nanoparticles into a polymer matrix. (<b>A</b>) Neat polymer (diffusing gas molecules follow a pathway perpendicular to the film orientation); (<b>B</b>) non-interacting nanocomposite (impermeable platelets hinders direct diffusion); (<b>C</b>) interacting nanocomposite (the polymer strands are “immobilized” at the polymer–nanofiller interface and the overall free volume available is reduced.</p> Full article ">Figure 12
<p>Example of the typical structure of the 2:1 layered silicates. Redrawn from [<a href="#B212-polymers-14-01626" class="html-bibr">212</a>] with permission of Elsevier. Copyright © 2015.</p> Full article ">Figure 13
<p>From left to right: (<b>A</b>) TEM image of PLA based nanocomposite films containing 6 wt% CH 30B along with oxygen and WVP values of untreated nanocomposites and annealed at 130 °C for 10 min as a function of nanoclay content. Adapted from [<a href="#B231-polymers-14-01626" class="html-bibr">231</a>] with permission of Wiley Periodicals. Copyright © 2016. (<b>B</b>) TEM and SEM images of PLA-CH 30B nanocomposites along with the relative oxygen permeability of nanocomposites with different volume fraction of clays (CNa:CH Na<sup>+</sup>, CRDP:Fyrolflex, and C30B:CH 30B). Adapted from [<a href="#B234-polymers-14-01626" class="html-bibr">234</a>] with permission from Elsevier. Copyright © 2016.</p> Full article ">Figure 14
<p>TEM image of (<b>A</b>) neat PLA and (<b>B</b>) the PLA–NCFHL biocomposite (with lignin) in which fibrils were well embedded within the PLA matrix (indicated by arrows); (<b>C</b>) confocal laser microscope image showing well dispersed lignin fibrils on the PLA surface; (<b>D</b>) Water vapor transmission rate of the neat PLA and PLA/lignin biocomposite. Adapted from [<a href="#B248-polymers-14-01626" class="html-bibr">248</a>] with permission from American Chemical Society. Copyright © 2018.</p> Full article ">Figure 15
<p>(<b>A</b>) TEM images of surface coated PLA nanocomposites filled with 1 and 3 wt% of ZnO nanoparticles (even dispersion), adapted from [<a href="#B262-polymers-14-01626" class="html-bibr">262</a>] with permission from Elsevier. Copyright© 2013. (<b>B</b>) SEM images of PLA nanocomposites containing 1–1.5 wt% of ZnO without any surface treatment (particle agglomeration indicated by red arrows), adapted from [<a href="#B158-polymers-14-01626" class="html-bibr">158</a>] with permission of Elsevier. Copyright © 2018.</p> Full article ">Figure 16
<p>(<b>A</b>) Schematic synthesis of semicrystalline or amorphous poly(isobutylene)-graft-acetylated poly(lactide) (PIB-g-(P(L)LA−Ac)). (<b>B</b>) Comparison of oxygen permeability values between the newly synthesized polymers and common ones. Adapted from [<a href="#B274-polymers-14-01626" class="html-bibr">274</a>] with permission from American Chemical Society. Copyright © 2020.</p> Full article ">Figure 17
<p>Representations of PLA nanoparticles using (<b>A</b>) full atoms (FA), (<b>B</b>) united atoms (UA), and (<b>C</b>) course grained (CG) methods.</p> Full article ">
18 pages, 3274 KiB  
Article
Hydrophobic Ag-Containing Polyoctylmethylsiloxane-Based Membranes for Ethylene/Ethane Separation in Gas-Liquid Membrane Contactor
by Evgenia Grushevenko, Alexey Balynin, Ruslan Ashimov, Stepan Sokolov, Sergey Legkov, Galina Bondarenko, Ilya Borisov, Morteza Sadeghi, Stepan Bazhenov and Alexey Volkov
Polymers 2022, 14(8), 1625; https://doi.org/10.3390/polym14081625 - 18 Apr 2022
Cited by 5 | Viewed by 2582
Abstract
The application of gas-liquid membrane contactors for ethane-ethylene separation seems to offer a good alternative to conventional energy-intensive processes. This work aims to develop new hydrophobic composite membranes with active ethylene carriers and to demonstrate their potential for ethylene/ethane separation in gas-liquid membrane [...] Read more.
The application of gas-liquid membrane contactors for ethane-ethylene separation seems to offer a good alternative to conventional energy-intensive processes. This work aims to develop new hydrophobic composite membranes with active ethylene carriers and to demonstrate their potential for ethylene/ethane separation in gas-liquid membrane contactors. For the first time, hybrid membrane materials based on polyoctylmethylsiloxane (POMS) and silver tetrafluoroborate, with a Si:Ag ratio of 10:0.11 and 10:2.2, have been obtained. This technique allowed us to obtain POMS-based membranes with silver nanoparticles (8 nm), which are dispersed in the polymer matrix. The dispersion of silver in the POMS matrix is confirmed by the data IR-spectroscopy, wide-angle X-ray diffraction, and X-ray fluorescence analyses. These membranes combine the hydrophobicity of POMS and the selectivity of silver ions toward ethylene. It was shown that ethylene sorption at 600 mbar rises from 0.89 cm3(STP)/g to 3.212 cm3(STP)/g with an increase of Ag content in POMS from 0 to 9 wt%. Moreover, the membrane acquires an increased sorption affinity for ethylene. The ethylene/ethane sorption selectivity of POMS is 0.64; for the membrane with 9 wt% silver nanoparticles, the ethylene/ethane sorption selectivity was 2.46. Based on the hybrid material, POMS-Ag, composite membranes were developed on a polyvinylidene fluoride (PVDF) porous support, with a selective layer thickness of 5–10 µm. The transport properties of the membranes were studied by separating a binary mixture of ethylene/ethane at 20/80% vol. It has been shown that the addition of silver nanoparticles to the POMS matrix leads to a decrease in the ethylene permeability, but ethylene/ethane selectivity increases from 0.9 (POMS) to 1.3 (9 wt% Ag). It was noted that when the POMS-Ag membrane is exposed to the gas mixture flow for 3 h, the selectivity increases to 1.3 (0.5 wt% Ag) and 2.3 (9 wt% Ag) due to an increase in ethylene permeability. Testing of the obtained membranes in a gas-liquid contactor showed that the introduction of silver into the POMS matrix makes it possible to intensify the process of ethylene mass transfer by more than 1.5 times. Full article
(This article belongs to the Special Issue Polymers for Membrane Separation: Properties and Applications)
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<p>Scheme of POMS synthesis.</p> Full article ">Figure 2
<p>General view of a flat-frame membrane gas-liquid contactor (<b>a</b>) and overall scheme (<b>b</b>).</p> Full article ">Figure 3
<p>Types of POMS polymer films with the addition of a silver salt: (<b>a</b>) AgNO<sub>3</sub>, (<b>b</b>) AgBF<sub>4</sub>.</p> Full article ">Figure 4
<p>Types of POMS polymer films with the addition of AgBF<sub>4</sub>: (<b>a</b>) 1 wt%, (<b>b</b>) 20 wt%.</p> Full article ">Figure 5
<p>FTIR-spectra: 1, AgBF<sub>4</sub>; 2, POMS; 3, POMS-Ag1; 4, POMS-Ag9; 5, POMS 40:60. Adapted with permission from Ref. [<a href="#B45-polymers-14-01625" class="html-bibr">45</a>]. Copyright 2017, Pleiades Publishing, Ltd.</p> Full article ">Figure 6
<p>WAXD data: 1, POMS; 2, POMS-Ag1; 3, POMS-Ag9.</p> Full article ">Figure 7
<p>Sorption isotherms of ethane (solid line) and ethylene (dashed line) in POMS (square), POMS-Ag1 (circle), and POMS-Ag9 (triangle) at 35 °C.</p> Full article ">Figure 8
<p>Water vapor isotherms in POMS (square), POMS-Ag1 (circle), and POMS-Ag9 (triangle) at 35 °C.</p> Full article ">Figure 9
<p>SEM images of samples of the flat composite membranes: (<b>a</b>) POMS/MFFK, 6 µm; (<b>b</b>) Ag1/MFFK, 10 µm; (<b>c</b>) Ag9/MFFK, 8 µm.</p> Full article ">Figure 10
<p>Dependence of the ethylene mass transfer coefficient (K, filled shapes) and ethylene/ethane selectivity (hollow shapes) on the initial ethylene concentration in the mixture for Ag9/MFFK (blue) and POMS/MFFK (red) composite membranes.</p> Full article ">
15 pages, 2154 KiB  
Article
Mechanics of a Biomimetic Moisture Sensitive Actuator Based on Compression Wood
by Gerhard Sinn, Elisabeth Fizek, Rupert Wimmer and Helga Lichtenegger
Polymers 2022, 14(8), 1624; https://doi.org/10.3390/polym14081624 - 18 Apr 2022
Cited by 3 | Viewed by 2002
Abstract
Various mechanisms of plant organ movements have been reported, including the close association of two layers with expressed differences in hygroscopic properties. Following this principle, actuator beams composed of thin veneers out of normal and compression wood cut from Scots pine (Pinus [...] Read more.
Various mechanisms of plant organ movements have been reported, including the close association of two layers with expressed differences in hygroscopic properties. Following this principle, actuator beams composed of thin veneers out of normal and compression wood cut from Scots pine (Pinus sylvestris L.) were prepared by using two types of adhesives. The mismatch of the swelling properties of the two layers in tight combination resulted in an expressed bending deflection in response to set humidity changes. The resulting curvatures were measured and analyzed by the Timoshenko bi-metal-model, as well as with an enhanced three-layer model, with the latter also considering the mechanical influence of the glueline on the actuator bending. The thermally induced strain in the original model was replaced by another strain due to moisture changes. The strain was modelled as a function of wood density, along with changes in wood moisture. Experiments with free movement of the bilayer to measure curvature, and with constraints to determine forces, were performed as well. Deformation and magnitude of actuators movements were in close agreement with the enhanced bilayer-model for the phenol-resorcinol-formaldehyde adhesive, which deviated substantially from the casein adhesive glued actuators. The obtained results are seen as critical for wood-based actuator systems that are potentially used in buildings or other applications. Full article
(This article belongs to the Special Issue Advances in Wood-Based Materials and Wood Polymer Composites)
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<p>Sorption Isotherms of normal (squares) and compression wood (circles) of reference strips.</p> Full article ">Figure 2
<p>Swelling of normal wood as a function of the product density times moisture content.</p> Full article ">Figure 3
<p>Swelling of compression wood as a function of the product density times moisture content.</p> Full article ">Figure 4
<p>Relative change of curvatures of tri-layer model compared to bilayer model as a function of thickness of adhesive layer: dashed line, bilayer-reference; dotted line, adhesive forms a distinguishable glueline; solid line, adhesive penetrates wood and forms an interlayer.</p> Full article ">Figure 5
<p>Experimental curvatures for bilayers made with casein adhesive (squares) and PRF adhesive (circles).</p> Full article ">Figure 6
<p>Prediction of simple Timoshenko-model with density-dependent strains.</p> Full article ">Figure 7
<p>Prediction of multilayer Timoshenko-model with density-dependent strains.</p> Full article ">Figure 8
<p>Actuator forces for CAS and PRF bilayers as a function of time and steps of relative humidity.</p> Full article ">
10 pages, 4476 KiB  
Article
Novel Mutations in Putative Nicotinic Acid Phosphoribosyltransferases of Mycobacterium tuberculosis and Their Effect on Protein Thermodynamic Properties
by Yu-Juan Zhang, Muhammad Tahir Khan, Madeeha Shahzad Lodhi, Hadba Al-Amrah, Salma Saleh Alrdahe, Hanan Ali Alatawi and Doaa Bahaa Eldin Darwish
Polymers 2022, 14(8), 1623; https://doi.org/10.3390/polym14081623 - 18 Apr 2022
Viewed by 2090
Abstract
pncB1 and pncB2 are two putative nicotinic acid phosphoribosyltransferases, playing a role in cofactor salvage and drug resistance in Mycobacterium tuberculosis. Mutations have been reported in first- and second-line drug targets, causing resistance. However, pncB1 and pncB2 mutational data are not available, [...] Read more.
pncB1 and pncB2 are two putative nicotinic acid phosphoribosyltransferases, playing a role in cofactor salvage and drug resistance in Mycobacterium tuberculosis. Mutations have been reported in first- and second-line drug targets, causing resistance. However, pncB1 and pncB2 mutational data are not available, and neither of their mutation effects have been investigated in protein structures. The current study has been designed to investigate mutations and also their effects on pncB1 and pncB2 structures. A total of 287 whole-genome sequenced data of drug-resistant Mycobacterium tuberculosis isolates from Khyber Pakhtunkhwa of Pakistan were retrieved (BioSample PRJEB32684, ERR2510337-ERR2510445, ERR2510546-ERR2510645) from NCBI. The genomic data were analyzed for pncB1 and pncB2 mutations using PhyResSE. All the samples harbored numerous synonymous and non-synonymous mutations in pncB1 and pncB2 except one. Mutations Pro447Ser, Arg286Arg, Gly127Ser, and delTCAGGCCG1499213>1499220 in pncB1 are novel and have not been reported in literature and TB databases. The most common non-synonymous mutations exhibited stabilizing effects on the pncB1 structure. Moreover, 36 out of 287 samples harbored two non-synonymous and 34 synonymous mutations in pncB2 among which the most common was Phe204Phe (TTT/TTC), present in 8 samples, which may have an important effect on the usage of specific codons that may increase the gene expression level or protein folding effect. Mutations Ser120Leu and Pro447Ser, which are present in the loop region, exhibited a gain in flexibility in the surrounding residues while Gly429Ala and Gly127Ser also demonstrated stabilizing effects on the protein structure. Inhibitors designed based on the most common pncB1 and pncB2 mutants may be a more useful strategy in high-burden countries. More studies are needed to elucidate the effect of synonymous mutations on organism phenotype. Full article
(This article belongs to the Special Issue Nucleic Acids as Polymers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Ramachandran plot of modeled structure nicotinate phosphoribosyltransferases. Among 371 amino acids, 347 (93.5%) residues have been modeled in the favorable regions and 6.5% in the allowed region.</p> Full article ">Figure 2
<p>Mutation effect on the <span class="html-italic">pncB1</span> structure. The location of the mutations is encircled in blue. These mutations are present in the loop regions. Mutations Ser120Leu and Pro447Ser are present in the loop region and exhibited a gain in flexibility in the surrounding residues (red). Gly429Ala and Gly127Ser also demonstrated stabilizing effects on the protein structure.</p> Full article ">Figure 3
<p>Secondary structure of wild type (WT) and mutant <span class="html-italic">pncB1</span> protein. Secondary structure was predicted using the PSIPRED server. The position of the mutations is shown with a green circle. Residues with black circles changed into loop mutants when compared with WT.</p> Full article ">Figure 4
<p>WT and mutant <span class="html-italic">pncB1</span> protein secondary structure. This structure has Helices 18 and 23 strands. The position of the mutations is shown with a green circle while a black circle shows the histidine residues that changed into a loop in mutant <span class="html-italic">pncB1</span>.</p> Full article ">Figure 5
<p><span class="html-italic">pncB1</span> model validation. (<b>A</b>) AlphaFold per-residue confidence score (pLDDT). (<b>B</b>) The color at position (x, y) indicates AlphaFold’s expected position error at residue x, when the predicted and true structures are aligned on residue y. (<b>C</b>) ProsA validation modeled <span class="html-italic">pncB1</span> (Z-score −9.44).</p> Full article ">
14 pages, 3537 KiB  
Article
Melting Temperature Depression of Polymer Single Crystals: Application to the Eco-Design of Tie-Layers in Polyolefinic-Based Multilayered Films
by Juan F. Vega, Virginia Souza-Egipsy, M. Teresa Expósito and Javier Ramos
Polymers 2022, 14(8), 1622; https://doi.org/10.3390/polym14081622 - 17 Apr 2022
Cited by 2 | Viewed by 2456
Abstract
In this paper, we describe a method for determining polymer compatibility, which will aid in establishing the requirements of polyolefinic materials for the eco-design of multilayer films for mechanical recycling while avoiding the use of reactive tie layers. Our ultimate goal is to [...] Read more.
In this paper, we describe a method for determining polymer compatibility, which will aid in establishing the requirements of polyolefinic materials for the eco-design of multilayer films for mechanical recycling while avoiding the use of reactive tie layers. Our ultimate goal is to define the molecular characteristics of the polyolefinic structural layer that improve compatibility with the tie layer during mechanical recycling. We have investigated the melting temperature depression of single crystals of various polyethylenes embedded in commercial polymeric matrices with various functionalities (ester, acrylate, acetate and methacrylic acid sodium ionomer), which can be potentially used as tie layers. We demonstrate how the concentration and molecular architecture of the matrices affect the melting temperature of the embedded single crystals differently depending on the latter’s molecular architecture. The main finding indicates that the tie layers are more compatible with linear polyethylene than with branched polyethylenes. Indeed, our results show that the heterogeneous Ziegler–Natta linear low-density polyethylene is incompatible with all of the tie layers tested. The depression of melting temperatures observed are in excellent agreement with the results obtained by investigating the rheological behaviour and morphological features of solution-mixed blends in which segmental interactions between polymeric chains have been, in theory, maximized. Because Ziegler–Natta linear density polyethylene is one of the most commonly used polymers as a structural layer in multi-layer applications, the findings of this study are useful as they clearly show the unsuitability of this type of polyethylene for recycling from an eco-design standpoint. The specific molecular requirements for polyethylene layers (branching content less than 0.5/100 carbon atoms) can be specified for use in packaging, guiding the eco-design and valorisation of recycled multi-layered films containing this material. Full article
(This article belongs to the Section Polymer Applications)
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<p>TEM images of the single crystals in PE00, PE0.3, PE0.5 and PE_ZN samples. The bars correspond to a size scale of 1 μm in all cases.</p> Full article ">Figure 2
<p>DSC traces of the single crystals of the polyethylenes (<b>left</b>) and matrices (<b>right</b>) at a heating rate of 10 °C·min<sup>−1</sup>.</p> Full article ">Figure 3
<p>DSC melting traces of PE0.0 (<b>left</b>) and PE_ZN (<b>right</b>) single crystals mixtures (25/75) with the different branched matrices: (<b>A</b>) whole DSC traces and (<b>B</b>) detail of PE single crystals melting zone. The dashed line indicates the melting temperature of the corresponding single crystals.</p> Full article ">Figure 4
<p>Melting peak temperature compositional dependence for PE0.0 (solid symbols) and PE_ZN (hollow symbols) mixed with EEA (circles), EVA (up triangles), EMAANa (down triangles) and PCL (squares).</p> Full article ">Figure 5
<p>DSC melting traces of PE0.0 (<b>A</b>), PE0.3 (<b>B</b>), PE0.5 (<b>C</b>) and PE_ZN (<b>D</b>) single crystals mixtures with EVA in the whole compositional range.</p> Full article ">Figure 6
<p>(<b>A</b>) Compositional dependence of the melting temperature of the single crystals embedded in EVA matrix. (<b>B</b>) Melting temperature depression of the mixtures studied: PE0.0 (squares), PE0.3 (circles), PE0.5 (down triangles) and PE_ZN (up triangles). The dotted line indicates the behaviour of HDPE single crystals embedded in LDPE from the literature [<a href="#B29-polymers-14-01622" class="html-bibr">29</a>].</p> Full article ">Figure 7
<p>(<b>A</b>) Storage (□) and loss (Ο) moduli and (<b>B</b>) out-of-phase component of complex viscosity (σ) versus angular frequency for PE0.0/EVA 80/20 blend (<b>left</b>) and PE_ZN/EVA 80/20 (<b>right</b>) at T = 150 °C. The dotted curves are the calculations for a miscible blend. The solid lines represent the results of the Palierne model for immiscible blends with α/R = 0.8 kN·m<sup>−2</sup>. The dashed lines represent the behaviour obtained for a partially miscible blend with X = 0.6 and α/R = 0.8 kN·m<sup>−2</sup>.</p> Full article ">Figure 8
<p>Micrographs obtained by AFM of the surface of thin films of PE0.0/EVA 80/20 blend (<b>A</b>) and PE_ZN/EVA 80/20 (<b>B</b>).</p> Full article ">
15 pages, 1497 KiB  
Review
Liquefaction of Cellulose for Production of Advanced Porous Carbon Materials
by Arjeta Kryeziu, Václav Slovák and Alžběta Parchaňská
Polymers 2022, 14(8), 1621; https://doi.org/10.3390/polym14081621 - 16 Apr 2022
Cited by 9 | Viewed by 4939
Abstract
Cellulose is a renewable resource for the production of advanced carbonaceous materials for various applications. In addition to direct carbonization, attention has recently been paid to the preparation of porous carbons from liquid cellulose-based precursors. Possible pathways of cellulose conversion to a liquid [...] Read more.
Cellulose is a renewable resource for the production of advanced carbonaceous materials for various applications. In addition to direct carbonization, attention has recently been paid to the preparation of porous carbons from liquid cellulose-based precursors. Possible pathways of cellulose conversion to a liquid state suitable for the preparation of porous carbons are summarized in this review. Hydrothermal liquefaction leading to liquid mixtures of low-molecular-weight organics is described in detail together with less common decomposition techniques (microwave or ultrasound assisted liquefaction, decomposition in a strong gravitation field). We also focus on dissolution of cellulose without decomposition, with special attention paid to dissolution of nonderivatized cellulose. For this purpose, cold alkalines, hot acids, ionic liquids, or alcohols are commonly used. Full article
(This article belongs to the Topic Cellulose and Cellulose Derivatives)
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<p>Schematic representation of biomass/cellulose liquefactions.</p> Full article ">Figure 2
<p>Major components of pyrolytic bio-oil [<a href="#B29-polymers-14-01621" class="html-bibr">29</a>].</p> Full article ">Figure 3
<p>Decomposition products during cellulose liquefaction.</p> Full article ">Figure 4
<p>Cellulose solvents.</p> Full article ">
21 pages, 3082 KiB  
Review
Mechanical and Moisture Barrier Properties of Epoxy–Nanoclay and Hybrid Epoxy–Nanoclay Glass Fibre Composites: A Review
by Necar Merah, Farhan Ashraf and Mian M. Shaukat
Polymers 2022, 14(8), 1620; https://doi.org/10.3390/polym14081620 - 16 Apr 2022
Cited by 18 | Viewed by 3661
Abstract
Epoxy clay nanocomposites have been proven to have improved mechanical, thermal and physical properties over pristine matrix. Thus, the fields of application of epoxy–clay nanocomposites along with their hybrid glass/carbon fibre reinforced composites have grown tremendously during the last few decades. The present [...] Read more.
Epoxy clay nanocomposites have been proven to have improved mechanical, thermal and physical properties over pristine matrix. Thus, the fields of application of epoxy–clay nanocomposites along with their hybrid glass/carbon fibre reinforced composites have grown tremendously during the last few decades. The present review paper covers the research work performed on epoxy clay nanocomposites. It includes the influence of the processing techniques and parameters on the morphology of the nanocomposite, the methods of characterization and the effects of adding nanoclay on the mechanical and physical properties of composite. The improvements in the liquid barrier properties brought about by the addition of nanoclay platelets to epoxy resin are discussed. The variation of physical and mechanical properties with nanoclay type and content are reviewed along with the effects of moisture uptake on these properties. The advances in the development, characterization and applications of hybrid glass fibre reinforced epoxy–clay nanocomposites are discussed. Findings of the research work on the influence of nanoclay addition and exposure to water laden atmospheres on the behaviour of the hybrid glass fibre epoxy–nanoclay composites are presented. Finally, the potential health and environmental issues related to nanomaterials and their hybrid composites are reviewed. Full article
(This article belongs to the Special Issue Polymer Composite Analysis and Characterization)
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<p>Epoxy group.</p> Full article ">Figure 2
<p>The structure of a 2-D layered silicate. Reproduced from [<a href="#B34-polymers-14-01620" class="html-bibr">34</a>] with permission from Elsevier. (Copyright 2022, Elsevier).</p> Full article ">Figure 3
<p>Structure of composites arising from the intercalation of layered silicates and polymers: Ref. [<a href="#B35-polymers-14-01620" class="html-bibr">35</a>]. Reproduced from [<a href="#B34-polymers-14-01620" class="html-bibr">34</a>] with permission from Elsevier. (Copyright 2022, Elsevier).</p> Full article ">Figure 4
<p>TEM images of (<b>a</b>) exfoliation and (<b>b</b>) intercalation structure of DGEBA-MDA and DGEBA-DDS systems respectively. Scale bar corresponds to 20 nm [<a href="#B63-polymers-14-01620" class="html-bibr">63</a>]. Reproduced from [<a href="#B63-polymers-14-01620" class="html-bibr">63</a>] with permission from ACS Publications.</p> Full article ">Figure 5
<p>Variation of percent weight gain (water) with the square root of exposure time [<a href="#B29-polymers-14-01620" class="html-bibr">29</a>]. ((2013, Springer Nature).</p> Full article ">Figure 6
<p>Effects of I.30E clay loading on the (<b>a</b>) the tensile strength and (<b>b</b>) the modulus of elasticity and fracture strain of DGEBA epoxy from [<a href="#B29-polymers-14-01620" class="html-bibr">29</a>]. (2013, Springer Nature).</p> Full article ">Figure 7
<p>Effect of water uptake on flexural strength of GFRE and GFRE-nc at room temperature (RT) an 80 °C: (Zero (0) on the abscissa represents glass fibre reinforced epoxy with no clay addition).</p> Full article ">
25 pages, 6045 KiB  
Article
Evaluation of Antimicrobial and Anti-Biofilm Formation Activities of Novel Poly(vinyl alcohol) Hydrogels Reinforced with Crosslinked Chitosan and Silver Nano-Particles
by Reem T. Alfuraydi, Fahad M. Alminderej and Nadia A. Mohamed
Polymers 2022, 14(8), 1619; https://doi.org/10.3390/polym14081619 - 16 Apr 2022
Cited by 30 | Viewed by 3842
Abstract
Novel hydrogels were prepared by blending chitosan and poly(vinyl alcohol), PVA, then crosslinking the resulting blends using trimellitic anhydride isothiocyanate at a concentration based on chitosan content in the blends. The weight ratios of chitosan: PVA in the blends were 1:3, 1:1, and [...] Read more.
Novel hydrogels were prepared by blending chitosan and poly(vinyl alcohol), PVA, then crosslinking the resulting blends using trimellitic anhydride isothiocyanate at a concentration based on chitosan content in the blends. The weight ratios of chitosan: PVA in the blends were 1:3, 1:1, and 3:1 to produce three hydrogels symbolized as H13, H11, and H31, respectively. For a comparison, H10 was also prepared by crosslinking pure chitosan with trimellitic anhydride isothiocyanate. For further modification, three H31/silver nanocomposites (AgNPs) were synthesized using three different concentrations of silver nitrate to obtain H31/AgNPs1%, H31/AgNPs3% and H31/AgNPs5%. The structures of the prepared samples were emphasized using various analytical techniques. PVA has no inhibition activity against the tested microbes and biofilms. The antimicrobial and anti-biofilm formation activities of the investigated samples was arranged as: H31/AgNPs5% ≥ H31/AgNPs3% > H31/AgNPs1% > H10 > H31 > H11 > H13 > chitosan. H31/AgNPs5% and H31/AgNPs3% were more potent than Vancomycin and Amphotericin B against most of the tested microbes. Interestingly, H31 and H31/AgNPs3% were safe on the normal human cells. Consequently, hydrogels resulting from crosslinked blends of chitosan and PVA loaded with AgNPs in the same structure have significantly reinforced the antimicrobial and inhibition activity against the biofilms of PVA. Full article
(This article belongs to the Topic Advances in Biomaterials)
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<p>FTIR spectra of chitosan, PVA, H<sub>10</sub>, H<sub>13</sub>, H<sub>11</sub> and H<sub>31</sub>.</p> Full article ">Figure 2
<p>FTIR spectra of H<sub>31</sub> and its AgNP composites.</p> Full article ">Figure 3
<p>XPS spectrum of H<sub>31</sub>/AgNPs5% composite.</p> Full article ">Figure 4
<p>XRD patterns of chitosan, H<sub>10</sub>, PVA, H<sub>13</sub>, H<sub>11</sub> and H<sub>31</sub>.</p> Full article ">Figure 5
<p>XRD patterns of: (<b>a</b>) H<sub>31</sub>/AgNPs3% and (<b>b</b>) H<sub>31</sub>/AgNPs5% composites.</p> Full article ">Figure 6
<p>SEM images of chitosan, H<sub>10</sub>, PVA, H<sub>13</sub>, H<sub>11</sub> and H<sub>31</sub>.</p> Full article ">Figure 7
<p>SEM images of: (<b>a</b>) H<sub>31</sub>/AgNPs1%; (<b>b</b>) H<sub>31</sub>/AgNPs3% and (<b>c</b>) EDS of H<sub>31</sub>/AgNPs3%.</p> Full article ">Figure 8
<p>TEM images of H<sub>31</sub>/AgNPs5% composite at different magnifications: (<b>a</b>) 200 nm and (<b>b</b>) 100 nm.</p> Full article ">Figure 9
<p>MIC values of: (<b>a</b>) hydrogels and (<b>b</b>) H<sub>31</sub>/AgNP composites against the tested Gram-negative bacteria.</p> Full article ">Figure 10
<p>MIC values of: (<b>a</b>) hydrogels and (<b>b</b>) AgNP composites against the tested Gram-positive bacteria.</p> Full article ">Figure 11
<p>MIC values of: (<b>a</b>) hydrogels and (<b>b</b>) AgNP composites against the tested fungi.</p> Full article ">Figure 12
<p>Normal images of anti-biofilm conduct of the prepared hydrogels against <span class="html-italic">A. baumannii, B. subtilis</span>, and <span class="html-italic">C. albicans</span>.</p> Full article ">Figure 13
<p>Cytotoxicity inhibitory effect of H<sub>31</sub> and H<sub>31</sub>/AgNP3% against normal human lung fibroblast cells.</p> Full article ">Scheme 1
<p>Preparation of the trimellitic anhydride isothiocyanate cross linker.</p> Full article ">Scheme 2
<p>Preparation of crosslinked chitosan hydrogel.</p> Full article ">Scheme 3
<p>Synthesis of H<sub>31</sub>/AgNPs composite.</p> Full article ">
21 pages, 4258 KiB  
Article
Cold Plasma-Based Fabrication and Characterization of Active Films Containing Different Types of Myristica fragrans Essential Oil Emulsion
by Bara Yudhistira, Andi Syahrullah Sulaimana, Fuangfah Punthi, Chao-Kai Chang, Chun-Ta Lung, Shella Permatasari Santoso, Mohsen Gavahian and Chang-Wei Hsieh
Polymers 2022, 14(8), 1618; https://doi.org/10.3390/polym14081618 - 16 Apr 2022
Cited by 19 | Viewed by 3115
Abstract
Myristica fragrans essential oil (MFEO) is a potential active compound for application as an active packaging material. A new approach was developed using a cold plasma treatment to incorporate MFEO to improve the optical, physical, and bacterial inhibition properties of the film. The [...] Read more.
Myristica fragrans essential oil (MFEO) is a potential active compound for application as an active packaging material. A new approach was developed using a cold plasma treatment to incorporate MFEO to improve the optical, physical, and bacterial inhibition properties of the film. The MFEO was added as coarse emulsion (CE), nanoemulsion (NE), and Pickering emulsion (PE) at different concentrations. The PE significantly affected (p < 0.05) the optical, physical, and chemical properties compared with CE and NE films. The addition of MFEO to low-density polyethylene (LDPE) film significantly reduced water vapor permeability (WVP) and oxygen permeability (OP) and showed marked activity against E. coli and S. aureus (p < 0.05). The release rate of PE films after 30 h was 70% lower than that of CE and NE films. Thus, it can be concluded that the fabrication of active packaging containing MFEO is a potential food packaging material. Full article
(This article belongs to the Special Issue Polymeric Materials for Food Packaging II)
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Full article ">Figure 1
<p>ATR–FTIR of LDPE film treated with cold plasma containing CE-, NE-, and PE-stabilized MFEO.</p> Full article ">Figure 2
<p>Surface characterization of plasma-treated LDPE film coated with different type of emulsion (<b>a</b>) Control (<b>b</b>) CE 6% (<b>c</b>) NE 6% and (<b>d</b>) PE 6% observed under 10,000× magnification.</p> Full article ">Figure 2 Cont.
<p>Surface characterization of plasma-treated LDPE film coated with different type of emulsion (<b>a</b>) Control (<b>b</b>) CE 6% (<b>c</b>) NE 6% and (<b>d</b>) PE 6% observed under 10,000× magnification.</p> Full article ">Figure 2 Cont.
<p>Surface characterization of plasma-treated LDPE film coated with different type of emulsion (<b>a</b>) Control (<b>b</b>) CE 6% (<b>c</b>) NE 6% and (<b>d</b>) PE 6% observed under 10,000× magnification.</p> Full article ">Figure 3
<p>Effectiveness of LDPE film treated with cold plasma containing CE-, NE-, and PE-stabilized MFEO. (<b>a</b>) Total phenolic content; (<b>b</b>) antioxidant activity through the DPPH radical scavenging assay. <sup>a–c</sup> The values with different superscripts are significantly different at <span class="html-italic">p</span> &lt; 0.05. The error bars represent the standard deviations (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 4
<p>Effectiveness of LDPE film treated with cold plasma containing CE-, NE-, and PE-stabilized MFEO. (<b>a</b>) antimicrobial assay against <span class="html-italic">S. aureus</span>, (<b>b</b>) antimicrobial assay against <span class="html-italic">E. coli</span>. <sup>a–e</sup> The values with different superscripts are significantly different at <span class="html-italic">p</span> &lt; 0.05. The error bars represent the standard deviations (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 5
<p>Release rate of LDPE film treated with cold plasma containing CE-, NE-, and PE-stabilized MFEO in 95% alcohol. Values with different superscripts are significantly different at <span class="html-italic">p</span> &lt; 0.05. The error bars represent the standard deviation (<span class="html-italic">n</span> = 3).</p> Full article ">
25 pages, 23380 KiB  
Review
TiO2 Containing Hybrid Composite Polymer Membranes for Vanadium Redox Flow Batteries
by Gowthami Palanisamy and Tae Hwan Oh
Polymers 2022, 14(8), 1617; https://doi.org/10.3390/polym14081617 - 15 Apr 2022
Cited by 17 | Viewed by 4454
Abstract
In recent years, vanadium redox flow batteries (VRFB) have captured immense attraction in electrochemical energy storage systems due to their long cycle life, flexibility, high-energy efficiency, time, and reliability. In VRFB, polymer membranes play a significant role in transporting protons for current transmission [...] Read more.
In recent years, vanadium redox flow batteries (VRFB) have captured immense attraction in electrochemical energy storage systems due to their long cycle life, flexibility, high-energy efficiency, time, and reliability. In VRFB, polymer membranes play a significant role in transporting protons for current transmission and act as barriers between positive and negative electrodes/electrolytes. Commercial polymer membranes (such as Nafion) are the widely used IEM in VRFBs due to their outstanding chemical stability and proton conductivity. However, the membrane cost and increased vanadium ions permeability limit its commercial application. Therefore, various modified perfluorinated and non-perfluorinated membranes have been developed. This comprehensive review primarily focuses on recent developments of hybrid polymer composite membranes with inorganic TiO2 nanofillers for VRFB applications. Hence, various fabrications are performed in the membrane with TiO2 to alter their physicochemical properties for attaining perfect IEM. Additionally, embedding the -SO3H groups by sulfonation on the nanofiller surface enhances membrane proton conductivity and mechanical strength. Incorporating TiO2 and modified TiO2 (sTiO2, and organic silica modified TiO2) into Nafion and other non-perfluorinated membranes (sPEEK and sPI) has effectively influenced the polymer membrane properties for better VRFB performances. This review provides an overall spotlight on the impact of TiO2-based nanofillers in polymer matrix for VRFB applications. Full article
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<p>(<b>a</b>) Schematic representation of VRFB unit cell design and energy conversion process. Reprinted with permission from ref. [<a href="#B68-polymers-14-01617" class="html-bibr">68</a>]. Copyright © 2020 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim. (License Number: 5270131060091). (<b>b</b>) Schematic illustration of VRFB unit cell components. Proton transport mechanisms: (<b>c</b>) vehicular mechanism and (<b>d</b>) hopping mechanism. (<b>e</b>) Proton transport possibilities in polymer-nanoparticle hybrid composite membrane. Reprinted with permission from ref. [<a href="#B94-polymers-14-01617" class="html-bibr">94</a>]. Copyright © 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. (License Number: 5270141297621).</p> Full article ">Figure 2
<p>(<b>a</b>) Schematic representation of organic silica modified TiO<sub>2</sub>. (<b>b</b>) Vanadium ion crossover and (<b>c</b>) FTIR analysis of Nafion and modified Nafion membranes. Reprinted with permission from ref. [<a href="#B138-polymers-14-01617" class="html-bibr">138</a>]. Copyright © 2009 Elsevier B.V. (License Number: 5270100780394).</p> Full article ">Figure 3
<p>SEM cross-sectional view of (<b>a</b>) recast Nafion and (<b>b</b>) hybrid (rN212/T1.5) membranes. TiO<sub>2</sub> nanotube arrays: (<b>c</b>) top, (<b>d</b>) bottom, and (<b>e</b>) cross-sectional view of FE-SEM. (<b>f</b>) FTIR results of recast Nafion and hybrid (rN212/T1.5) membrane. (<b>g</b>,<b>h</b>) TEM and EDS mapping of TiO<sub>2</sub> nanotube—before and after soaking in VRFB electrolyte. (<b>i</b>) V<sup>4+</sup> ion cross-over, (<b>j</b>) vanadium permeability, and proton conductivity of membranes. (<b>k</b>) VRFB cell test of recast Nafion and rN212/T1.5 membranes. Reprinted with permission from ref. [<a href="#B68-polymers-14-01617" class="html-bibr">68</a>]. Copyright © 2020 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim. (License Number: 5270131060091).</p> Full article ">Figure 4
<p>Different DS and amount of TiO<sub>2</sub> nanoparticles in sPEEK/TiO<sub>2</sub> composite membranes: (<b>a</b>) ion exchange capacity, (<b>b</b>) Swelling ratio, and (<b>c</b>) water uptake. Different amount of TiO<sub>2</sub> nanoparticles in 5 h sPEEK/TiO<sub>2</sub> composite membranes: (<b>d</b>) proton conductivity, (<b>e</b>) vanadium ion permeability, (<b>f</b>) permeability and selectivity. VRFB cell performance of 5 h sPEEK/ 5% TiO<sub>2</sub> composite membranes: (<b>g</b>) charge-discharge cycle test, (<b>h</b>) efficiency, (<b>i</b>) normalized discharge capacity and (<b>j</b>) efficiencies at different current density. Reprinted with permission from ref. [<a href="#B141-polymers-14-01617" class="html-bibr">141</a>]. Copyright © 2017 Elsevier B.V. (License Number: 5270230374353).</p> Full article ">Figure 5
<p>SEM cross-sectional image of (<b>a</b>) before and (<b>b</b>,<b>c</b>) after cell test of sPEEK/TiO<sub>2</sub> double-deck membrane. (<b>d</b>) Vanadium ion permeability and selectivity (<b>e</b>) cycle performances (efficiency) of different membranes. Reprinted with permission from ref. [<a href="#B140-polymers-14-01617" class="html-bibr">140</a>]. Copyright © 2016 Elsevier B.V. (License Number: 5270241140135).</p> Full article ">Figure 6
<p>(<b>a</b>) FT-IR spectra of TiO<sub>2</sub> before and after sulphonation. (<b>b</b>) Vanadium ion permeability and selectivity, (<b>c</b>) coulombic efficiency, (<b>d</b>) voltage efficiency, (<b>e</b>) energy efficiency, and (<b>f</b>) cycle stability of membranes (Nafion117, sPEEK, sPEEK-TiO<sub>2</sub>, and sPEEK-s-TiO<sub>2</sub>). Reprinted with permission from ref. [<a href="#B126-polymers-14-01617" class="html-bibr">126</a>]. Copyright © 2019 Wiley Periodicals, Inc. (License Number: 5270521350593).</p> Full article ">Figure 7
<p>(<b>a</b>) Schematic representation of proton transport mechanism in the sPEEK-sTiO<sub>2</sub> membrane. (<b>b</b>) Vanadium ion permeability and (<b>c</b>) selectivity of sPEEK membrane with different loading of sTiO<sub>2</sub>. (<b>d</b>) Vanadium ion permeability and (<b>e</b>) selectivity of sPEEK-sTiO<sub>2</sub> membrane compared with other reported results. (<b>f</b>–<b>i</b>) VRFB unit cell performances of sPEEK-sTiO<sub>2</sub> hybrid membrane. Reprinted with permission from ref. [<a href="#B125-polymers-14-01617" class="html-bibr">125</a>]. Copyright © 2021 Elsevier Ltd. (License Number: 5270530067581).</p> Full article ">
13 pages, 4728 KiB  
Article
Effects of Modified Layered Double Hydroxides on the Thermal Degradation and Combustion Behaviors of Intumescent Flame Retardant Polyethylene Nanocomposites
by Tiefeng Zhang, Chunfeng Wang, Yue Wang, Yongliang Wang and Zhidong Han
Polymers 2022, 14(8), 1616; https://doi.org/10.3390/polym14081616 - 15 Apr 2022
Cited by 16 | Viewed by 2631
Abstract
The flame retardancy of layered double hydroxides (LDHs) correlates with their structure and dispersion in a polymeric matrix. To improve the flame retardant effectiveness of Mg-Al LDH in polyethylene (PE), 2-carboxy ethyl (phenyl) phosphinic acid (CEPPA) was adopted as a flame retardant modifier [...] Read more.
The flame retardancy of layered double hydroxides (LDHs) correlates with their structure and dispersion in a polymeric matrix. To improve the flame retardant effectiveness of Mg-Al LDH in polyethylene (PE), 2-carboxy ethyl (phenyl) phosphinic acid (CEPPA) was adopted as a flame retardant modifier to prepare CEPPA-intercalated LDH (CLDH) by the regeneration method, which was then exfoliated in PE by melt blending in the form of a masterbatch prepared from solution mixing. By compounding CLDH with intumescent flame retardant (IFR) composed of ammonium polyphosphate (APP) and pentaerythritol (PER), the thermal degradation and combustion behaviors of the flame retardant PE-based composites were investigated to reveal the flame retardant mechanism between CLDH and IFR in PE. The reactions between CLDH and IFR were revealed to make a predominant contribution to the compact and fully developed char of PE/IFR/CLDH, which enhanced the flame retardancy of the composites. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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Full article ">Figure 1
<p>(<b>a</b>) XRD patterns of LDH, CLDH, and their composites; (<b>b</b>) FTIR spectra of LDH and CLDH; (<b>c</b>) SEM micrograph of CLDH inserted with EDS spectrum of CLDH; (<b>d</b>) TEM micrograph of PE/PEgMA/CLDH.</p> Full article ">Figure 2
<p>TG curves of (<b>a</b>) LDHs and (<b>b</b>) IFR/LDHs.</p> Full article ">Figure 3
<p>(<b>a</b>) TG curves and (<b>b</b>) ΔWeight versus temperature curves of PE/IFR/LDHs.</p> Full article ">Figure 4
<p>The results of CONE, (<b>a</b>) HRR curves, (<b>b</b>) THR curves, (<b>c</b>) SPR curves, and (<b>d</b>) TSR curves.</p> Full article ">Figure 5
<p>Temperature versus time curves of the flame retardant composites during CONE testing.</p> Full article ">Figure 6
<p>SEM micrographs of the char after CONE Testing of the composites. (<b>a</b>) PE/IFR, (<b>b</b>) PE/IFR/LDH, (<b>c</b>) PE/IFR/SLDH, and (<b>d</b>) PE/IFR/CLDH.</p> Full article ">Figure 7
<p>XPS spectra of the char after CONE testing of the flame retardant composites. (<b>a</b>) Survey spectra, (<b>b</b>) C1s spectra, and (<b>c</b>) P2p spectra.</p> Full article ">Figure 8
<p>Schematic diagram of the flame retardant mechanism of PE/IFR/CLDH.</p> Full article ">
16 pages, 2348 KiB  
Article
Thermal Degradation of Photoluminescence Poly(9,9-dioctylfluorene) Solvent-Tuned Aggregate Films
by Kang Wei Chew, Nor Azura Abdul Rahim, Pei Leng Teh, Nurfatin Syafiqah Abdul Hisam and Siti Salwa Alias
Polymers 2022, 14(8), 1615; https://doi.org/10.3390/polym14081615 - 15 Apr 2022
Cited by 8 | Viewed by 2493
Abstract
The progression of the green emission spectrum during the decomposition of polyfluorenes (PFs) has impeded the development and commercialization of the materials. Herein, we constructed a solvent-tuned aggregated PFO film with the aim of retarding the material’s thermal degradation behavior which causes a [...] Read more.
The progression of the green emission spectrum during the decomposition of polyfluorenes (PFs) has impeded the development and commercialization of the materials. Herein, we constructed a solvent-tuned aggregated PFO film with the aim of retarding the material’s thermal degradation behavior which causes a significant decline in optical properties as a result of phase transformation. The tuning of the aggregate amount and distribution was executed by applying a poor alcohol-based solvent in chloroform. It emerges that at a lower boiling point methanol evaporates quickly, limiting the aggregate propagation in the film which gives rise to a more transparent film. Furthermore, because of the modulated β-phase conformation, the absorption spectra of PFO films were red-shifted and broadened. The increase in methanol percentage also led to a rise in β-phase percentage. As for the thermal degradation reactions, both pristine and aggregated PFO films exhibited apparent changes in the UV-Vis spectra and PL spectra. In addition, a 97:3 (chloroform:methanol) aggregated PFO film showed a more defined emission spectrum, which demonstrates that the existence of β-phase is able to suppress the unwanted green emission. Full article
(This article belongs to the Collection Assessment of the Ageing and Durability of Polymers)
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Full article ">Figure 1
<p>UV-Vis spectra of the PFO film and aggregated PFO films using various ratio of good to poor solvent of (<b>a</b>) ethanol, (<b>b</b>) isopropanol, and (<b>c</b>) methanol, and (<b>d</b>) normalised PL spectra for PFO and PFO with 97:3 induced aggregated films.</p> Full article ">Figure 2
<p>(<b>a</b>) UV-Vis absorption spectra of pristine PFO film and aggregated PFO films with different chloroform/methanol ratios and (<b>b</b>) the ratio of methanol content to the fraction of β-phase induced in aggregated films.</p> Full article ">Figure 3
<p>UV-Vis absorption spectra of (<b>a</b>) pristine PFO films and aggregated PFO films from chloroform/methanol with the ratio of (<b>b</b>) 97:3 and (<b>c</b>) 91:9, before and after the thermal degradation test.</p> Full article ">Figure 4
<p>UV-Vis absorption spectra of (<b>a</b>) pristine PFO film and (<b>c</b>) 97:3 aggregated PFO film, and PL intensity spectra of (<b>b</b>) pristine PFO film and (<b>d</b>) 97:3 aggregated PFO film, before and after thermal degradation test.</p> Full article ">Figure 5
<p>DSC heating curves of pristine PFO films and 97:3 aggregated PFO films before and after thermal degradation test at 90 °C for 72 h.</p> Full article ">Figure 6
<p>XRD analysis of (<b>a</b>) pristine PFO films and (<b>b</b>) 97:3 aggregated PFO films before and after thermal degradation test.</p> Full article ">Figure 7
<p>FTIR spectra of (<b>a</b>) pristine PFO films and (<b>b</b>) aggregated PFO films before and after thermal degradation test, respectively.</p> Full article ">Figure 8
<p>SEM images of (<b>a</b>) pristine PFO film, (<b>c</b>) 97:3 aggregated PFO film and (<b>e</b>) 91:9 aggregated PFO film, respectively, before the thermal degradation test. SEM images of (<b>b</b>) pristine PFO film, (<b>d</b>) 97:3 aggregated PFO film and (<b>f</b>) 91:9 aggregated PFO film, respectively, after thermal degradation test.</p> Full article ">Figure 9
<p>Thermal oxidation degradation pathway for aggregated PFO films.</p> Full article ">
16 pages, 2926 KiB  
Article
Investigation of XLPE Cable Insulation Using Electrical, Thermal and Mechanical Properties, and Aging Level Adopting Machine Learning Techniques
by Priya Selvamany, Gowri Sree Varadarajan, Naresh Chillu and Ramanujam Sarathi
Polymers 2022, 14(8), 1614; https://doi.org/10.3390/polym14081614 - 15 Apr 2022
Cited by 6 | Viewed by 3935
Abstract
Hydrothermal and chemical aging tests on a 230 kV cross-linked polyethylene (XLPE) insulation cable were carried out in the present study to evaluate the degradation and aging levels qualitatively. The samples were subjected to water aging at a temperature of 80 °C, and [...] Read more.
Hydrothermal and chemical aging tests on a 230 kV cross-linked polyethylene (XLPE) insulation cable were carried out in the present study to evaluate the degradation and aging levels qualitatively. The samples were subjected to water aging at a temperature of 80 °C, and in an aqueous ionic solution of CuSO4 at room temperature. The diffusion coefficient results indicated that the ion migration was not at the same rate in the aging conditions. The diffusion coefficient–D–of the sample immersed in an aqueous CuSO4 solution was lower than the hydrothermally aged specimens. The hydrophobicity of aged specimens decreased considerably compared to unaged samples. The distribution of trapped charges was quantitatively characterized. The presence of shallow trap energy states were observed in unaged XLPE, whereas the deep trap sites were noticed in aged specimens. In addition, the charge trap characteristics were different for positive and negative charge deposition. Various material characterization techniques, viz. dynamic mechanical analysis (DMA), tensile, contact angle, and LIBS, were further employed on the aged and virgin specimens. The tensile behavior of the hydrothermally aged specimen was degraded due to the oxidised regions, which had formed a weak spot against the mechanical stress. Reduced glass transition temperature and increased loss tangent measurements were noticed for aged specimens over their unaged counterparts. Machine learning techniques, such as the principal component analysis (PCA) and the artificial neural network (ANN) analysis, were performed on LIBS spectral data of the samples to classify the aging mechanisms qualitatively. Full article
(This article belongs to the Section Circular and Green Polymer Science)
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<p>Schematic representation of surface potential decay system.</p> Full article ">Figure 2
<p>Laser-induced breakdown spectroscopy setup.</p> Full article ">Figure 3
<p>Variation in % weight gain of XLPE specimen due to aging.</p> Full article ">Figure 4
<p>Droplet shape for (<b>a</b>) unaged, (<b>b</b>) CuSO<sub>4</sub>, and (<b>c</b>) hydrothermally aged surfaces.</p> Full article ">Figure 5
<p>Tensile stress-strain curves for unaged and aged XLPE.</p> Full article ">Figure 6
<p>Variation in surface potential decay curves for both polarities.</p> Full article ">Figure 7
<p>Variation in trap density as a function of trap depth for a ±DC input voltage.</p> Full article ">Figure 8
<p>Dynamic relaxation temperature spectra in (<b>a</b>) storage modulus E’, (<b>b</b>) loss modulus E”, and (<b>c</b>) mechanical loss factor for unaged, CuSO<sub>4</sub>, and hydrothermally aged XLPE samples.</p> Full article ">Figure 8 Cont.
<p>Dynamic relaxation temperature spectra in (<b>a</b>) storage modulus E’, (<b>b</b>) loss modulus E”, and (<b>c</b>) mechanical loss factor for unaged, CuSO<sub>4</sub>, and hydrothermally aged XLPE samples.</p> Full article ">Figure 9
<p>Activation energy plot for unaged and aged XLPE samples.</p> Full article ">Figure 10
<p>Emission spectra of XLPE sample in the wavelength 200–800 nm.</p> Full article ">Figure 11
<p>PCA loading plot of unaged and aged XLPE specimens (<b>a</b>) PC1, (<b>b</b>) PC2, and (<b>c</b>) PC3.</p> Full article ">Figure 12
<p>PCA score plot of test specimens classified with respect to the aging studies.</p> Full article ">Figure 13
<p>Confusion matrices of XLPE specimens classified with the test spectra of (<b>A</b>) unaged, (<b>B</b>) CuSO<sub>4</sub>, and (<b>C</b>) hydrothermally aged specimens.</p> Full article ">
18 pages, 4170 KiB  
Article
Expandable Graphite as a Multifunctional Flame-Retarding Additive for Highly Filled Thermal Conductive Polymer Formulations
by Florian Tomiak, Kevin Schneider, Angelina Schoeffel, Klaus Rathberger and Dietmar Drummer
Polymers 2022, 14(8), 1613; https://doi.org/10.3390/polym14081613 - 15 Apr 2022
Cited by 10 | Viewed by 3041
Abstract
Expandable graphite (EG) and graphite (G) were assessed as multifunctional additives improving both flame retardancy and thermal conductivity in highly filled, thermal conductive polymeric materials based on polyamide 6 (PA6). Fire testing was conducted using modern UL-94, LOI and cone calorimeter test setups. [...] Read more.
Expandable graphite (EG) and graphite (G) were assessed as multifunctional additives improving both flame retardancy and thermal conductivity in highly filled, thermal conductive polymeric materials based on polyamide 6 (PA6). Fire testing was conducted using modern UL-94, LOI and cone calorimeter test setups. It is demonstrated that thermal conductivity can significantly influence the time to ignition, although offering little fire resistance once ignited even in highly filled systems. Thus, for PA6 formulations containing solely 70 wt.% G, the peak heat release rate (pHRR) measured in cone calorimeter tests was 193 kW/m², whereas PA6 formulations containing 20 wt.% EG/50 wt.% G did not exhibit a measurable heat development. Particular attention was paid to effect separation between thermal conductivity and residue formation. Good thermal conductivity properties are proven to be particularly effective in test scenarios where the heat impact is comparatively low and the testing environment provides good heat dissipation and convective cooling possibilities. For candle-like ignition scenarios (e.g., LOI), filling levels of >50 wt.% (G or EG/G) are shown to be sufficient to suppress ignition exclusively by thermal conductivity. V0 classifications in UL-94 vertical burning tests were achieved for PA6 formulations containing ≥70 wt.% G, ≥25 wt.% EG and ≥20 wt.% EG/25 wt.% G. Full article
(This article belongs to the Special Issue Reinforced Polymer Composites III)
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<p>Microscopy images of graphite-filled PA6. Images were taken perpendicular to the injection-flow, as illustrated.</p> Full article ">Figure 2
<p>TGA analysis results for (<b>A</b>) PA6/G and (<b>B</b>) PA6/EG and PA6/G/EG formulations. Measurements were conducted under nitrogen atmosphere; a heating rate of 20 K/min was applied.</p> Full article ">Figure 3
<p>(<b>A</b>) Thermal conductivity measurements (4 mm) in (x) and thru-plane (z); (<b>B</b>) Illustrated injection molding plate and specimen extraction area.</p> Full article ">Figure 4
<p>Cone Calorimeter results for a recipe selection; EG: expandable graphite, G: Graphite; (<b>A</b>) PA6/G formulations (<b>B</b>) PA6/EG and PA6/EG/G formulations.</p> Full article ">Figure 5
<p>Important Cone Calorimeter key figures plotted against the PA6 weight fraction; (<b>A</b>) peak heat release rate (pHRR), (<b>B</b>) maximum of the average rate of heat release (MAHRE), (<b>C</b>) total heat emitted (THE) and (<b>D</b>) ignition time (t<sub>ign</sub>).</p> Full article ">Figure 6
<p>Selected images of char residues after cone calorimeter testing.</p> Full article ">Figure 7
<p>LOI and UL-94 testing results; (<b>A</b>) sample thickness 1 + 2 + 4 mm, (<b>B</b>) correlation study of thermal conductivity versus LOI.</p> Full article ">Figure 8
<p>LOI images—characterization and comparison of burning behavior in dependence of the filling degree.</p> Full article ">Figure 9
<p>Thermal imaging measurements in a candle-like ignition setup (e.g., LOI) under atmospheric conditions using a 50 W propane testing flame. (<b>A</b>) Maximum temperature plot over time for a material selection; (<b>B</b>) Thermal imaging plot after 120 s ignition.</p> Full article ">Figure 10
<p>Thermal imaging measurements in a bottom-exposed ignition setup (e.g., UL-94) under atmospheric conditions using a 50 W methane testing flame. (<b>A</b>) Maximum temperature plot over time for a material selection; (<b>B</b>) Thermal imaging plot after 30 s ignition.</p> Full article ">Figure 11
<p>(<b>A</b>) Temperature distribution of selected samples at 30 s flame exposure measured midway along the length. All curves were averaged over three measurements; (<b>B</b>) thermal images and illustrated measuring position.</p> Full article ">
20 pages, 7489 KiB  
Article
Implementation of Microwave Circuits Using Stereolithography
by Germán Torregrosa-Penalva, Héctor García-Martínez, Ángela E. Ortega-Argüello, Alberto Rodríguez-Martínez, Arnau Busqué-Nadal and Ernesto Ávila-Navarro
Polymers 2022, 14(8), 1612; https://doi.org/10.3390/polym14081612 - 15 Apr 2022
Cited by 5 | Viewed by 3052
Abstract
In this work, the use of additive manufacturing techniques through stereolithography for the manufacture of high-frequency circuits and devices is presented. Both the resin and the 3D printer used in this research are general-purpose commercial materials, not specifically intended for the implementation of [...] Read more.
In this work, the use of additive manufacturing techniques through stereolithography for the manufacture of high-frequency circuits and devices is presented. Both the resin and the 3D printer used in this research are general-purpose commercial materials, not specifically intended for the implementation of microwave networks. The manufacturing and metallization procedures used to produce substrates for the design of planar microwave circuits are described, introducing the characterization process carried out to determine the electrical properties of the resin used. The ultrasonic techniques that allow the structural analysis of the manufactured substrates are also described. The electrical characterization provides a relative dielectric permittivity of 3.25 and a loss tangent of 0.03 for the resin used. In addition, the structural analysis shows a homogeneity and a finish of the manufactured parts that is not achievable using fused deposition modeling techniques. Finally, as a proof of concept, the design and manufacture of a complex geometry stepped impedance filter on a multi-height substrate using stereolithography techniques is presented, which allows for reducing the size of the traditional implementation of the same filter while maintaining its high-frequency response performance. Full article
(This article belongs to the Special Issue Applications of 3D Printing for Polymers)
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<p>Photograph of the printer employed.</p> Full article ">Figure 2
<p>Printed circuit board manufacturing process with glued copper layer: (<b>a</b>) step by step description; (<b>b</b>) cross-section of the manufactured substrate; (<b>c</b>) transmission line end cross-section.</p> Full article ">Figure 3
<p>Printed circuit board manufacturing process with copper spray and electroplating: (<b>a</b>) step by step description; (<b>b</b>) cross-section of the manufactured substrate; (<b>c</b>) transmission line end cross-section.</p> Full article ">Figure 4
<p>Experimental setup for ultrasonic measurements.</p> Full article ">Figure 5
<p>Photograph (50 × 80 mm<sup>2</sup>) of the calibrating elements employed to measure and extract the electrical parameters of the resin substrate material and the fabrication process. Transmission lines are 850 μm wide and 50 mm long, and gaps in the ring resonator network are 360 μm.</p> Full article ">Figure 6
<p>Simulated (<b>blue</b>) and measured (<b>orange</b>) calibrating elements magnitude of scattering parameters for a <span class="html-italic">h</span> = 1 mm substrate height. (<b>a</b>) transmission line; (<b>b</b>) short stub; (<b>c</b>) long stub.</p> Full article ">Figure 7
<p>Simulated (<b>blue</b>) and measured (<b>orange</b>) calibrating elements phase of scattering parameters for a <span class="html-italic">h</span> = 1 mm substrate height. (<b>a</b>) transmission line; (<b>b</b>) short stub; (<b>c</b>) long stub.</p> Full article ">Figure 8
<p>Simulated (<b>blue</b>) and measured (<b>orange</b>) calibrating elements magnitude of scattering parameters for a <span class="html-italic">h</span> = 1.6 mm substrate height. (<b>a</b>) transmission line; (<b>b</b>) short stub; (<b>c</b>) long stub.</p> Full article ">Figure 9
<p>Simulated (<b>blue</b>) and measured (<b>orange</b>) calibrating elements phase of scattering parameters for a <span class="html-italic">h</span> = 1.6 mm substrate height. (<b>a</b>) transmission line; (<b>b</b>) short stub; (<b>c</b>) long stub.</p> Full article ">Figure 10
<p>Circuit elements employed to simulate the response of the 10 mm long quarter wavelength open-ended stub calibrating network.</p> Full article ">Figure 11
<p>Simulated (<b>blue</b>) and measured (<b>orange</b>) ring resonator network magnitude and phase of the transmission coefficient: (<b>a</b>) <span class="html-italic">h</span> = 1.0 mm substrate height; (<b>b</b>) <span class="html-italic">h</span> = 1.6 mm substrate height.</p> Full article ">Figure 12
<p>Simulated (<b>blue</b>) and measured (<b>orange</b>) magnitude of the scattering parameters for a 50 mm long transmission line (<span class="html-italic">w</span> = 0.85 mm) for the <span class="html-italic">h</span> = 1.6 mm substrate height: (<b>a</b>) just metallic paint is applied; (<b>b</b>) after electroplating is also carried out.</p> Full article ">Figure 13
<p>Fabricated low pass filter prototype: (<b>a</b>) before the deposition of copper metallic paint and electroplating process on the ground plane; (<b>b</b>) after the metallization procedure.</p> Full article ">Figure 14
<p>Final implementation of the low pass filter prototype: (<b>a</b>) after milling process of the top low and high impedance sections; (<b>b</b>) filter characterization using Anritsu 3680 universal test fixture.</p> Full article ">Figure 15
<p>Circuit under analysis: (<b>a</b>) top surface; (<b>b</b>) details of delamination in the boundary; (<b>c</b>) bottom surface; (<b>d</b>) details of inclusion/void.</p> Full article ">Figure 16
<p>C-scan: (<b>a</b>) thickness profile; (<b>b</b>) X section; (<b>c</b>) Y section.</p> Full article ">Figure 17
<p>Examples of 2D profiles of the inner composition at different depths. Inner scans provide useful information regarding the homogeneity of the fabricated structure and reveal the presence of voids, bubbles and other irregularities.</p> Full article ">Figure 18
<p>Circuit simulations (<b>blue</b>), electromagnetic simulations (<b>black</b>) and measurements (<b>orange</b>) of the scattering parameters for the low pass filter prototype.</p> Full article ">Figure 19
<p>Final implementation of the low pass filter prototype using a resin printed constant <span class="html-italic">h</span> = 0.7 mm high substrate.</p> Full article ">Figure 20
<p>Measured scattering parameters for the stepped substrate low pass filter (<b>solid line</b>) and the conventional design on a constant 0.7 mm high substrate (<b>dotted line</b>).</p> Full article ">
35 pages, 2910 KiB  
Review
Polymeric Coatings and Antimicrobial Peptides as Efficient Systems for Treating Implantable Medical Devices Associated-Infections
by Irina Negut, Bogdan Bita and Andreea Groza
Polymers 2022, 14(8), 1611; https://doi.org/10.3390/polym14081611 - 15 Apr 2022
Cited by 29 | Viewed by 6380
Abstract
Many infections are associated with the use of implantable medical devices. The excessive utilization of antibiotic treatment has resulted in the development of antimicrobial resistance. Consequently, scientists have recently focused on conceiving new ways for treating infections with a longer duration of action [...] Read more.
Many infections are associated with the use of implantable medical devices. The excessive utilization of antibiotic treatment has resulted in the development of antimicrobial resistance. Consequently, scientists have recently focused on conceiving new ways for treating infections with a longer duration of action and minimum environmental toxicity. One approach in infection control is based on the development of antimicrobial coatings based on polymers and antimicrobial peptides, also termed as “natural antibiotics”. Full article
(This article belongs to the Special Issue Advances in Polymer Devices for Cell Transplantation)
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<p>Overview of the polymeric—AMPs-based coatings for implantable medical devices surfaces.</p> Full article ">Figure 2
<p>Stimuli response of polymeric coatings.</p> Full article ">Figure 3
<p>Elementary osmotic pump drug release.</p> Full article ">Figure 4
<p>Structural features of AMPs.</p> Full article ">Figure 5
<p>Schematically representation of Gram-positive and Gram-negative bacteria membrane. Both types have similar cytoplasmic membranes. Gram-positive bacteria are protected by a thick layer of peptidoglycan which surrounds the cytoplasmic membrane. On the other hand, Gram-negative bacteria have a thin peptidoglycan layer and an additional outer membrane. The lipopolysaccharide makes up the majority of the outer sheet of the outer membrane, while phospholipids make up the inner leaflet.</p> Full article ">Figure 6
<p>The three major mechanisms of AMP activity.</p> Full article ">Figure 7
<p>Schematic representation of coatings which prevent microbial colonization. Created with <a href="http://BioRender.com" target="_blank">BioRender.com</a>.</p> Full article ">
18 pages, 10020 KiB  
Article
Phase Behaviors of ABA Star Polymer and Nanoparticles Confined in a Sphere with Soft Inner Surface
by Minna Sun, Zhiwei Zhang, Ying Li, Wen Li, Qingwei Liao and Lei Qin
Polymers 2022, 14(8), 1610; https://doi.org/10.3390/polym14081610 - 15 Apr 2022
Cited by 1 | Viewed by 1691
Abstract
The phase behaviors of an ABA star polymer and nanoparticles confined in a sphere with soft inner surface, which is grafted with homopolymer brushes have been studied by the self-consistent field theory (SCFT). The morphologies of mixture in the center slice of sphere [...] Read more.
The phase behaviors of an ABA star polymer and nanoparticles confined in a sphere with soft inner surface, which is grafted with homopolymer brushes have been studied by the self-consistent field theory (SCFT). The morphologies of mixture in the center slice of sphere were focused. Two cases are considered: one is that the nanoparticles interact with the B blocks and the other is that the nanoparticles preferentially wet the B blocks. Under the two conditions, through changing the block ratio of the ABA star polymer, the concentration and radius of the nanoparticles, the phase behaviors of the mixtures confined the soft sphere are studied systematically. With increasing the concentration of nanoparticles, the entropy and the steric repulsive interaction of nanoparticles, and the nanoparticle density distributions along the perpendicular line through the center of sphere are plotted. The phase diagram is also constructed to analyze the effects of the nanoparticle volume fraction and radius on morphologies of ABA star polymers, and to study the effect of confinement on the phase behaviors. The results in this work provide a useful reference for controlling the ordered structures in experiment, which is an effective way to fabricate the newly multifunctional materials. Full article
(This article belongs to the Section Polymer Physics and Theory)
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<p>Schematic diagram of the ABA star polymer-nanoparticles mixture confined in a sphere with soft inner surface. The polymer, the nanoparticles and brushes are represented in green, gold and blue, respectively.</p> Full article ">Figure 2
<p>The morphologies of the ABA star polymer blend without nanoparticles. (<b>a</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math> (<b>b</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.2</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.6</mn> </mrow> </semantics></math> (<b>c</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.3</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.4</mn> </mrow> </semantics></math>. The blue color represents the A blocks, the red color represents the B blocks.</p> Full article ">Figure 3
<p>(<b>a</b>–<b>c</b>) The morphologies of the mixture of ABA star polymer and nanoparticles confined in a sphere with soft inner surface; the blue color represents the A blocks and the brushes, the red color represents the B blocks. The nanoparticles disperse in A domain. (<b>a1</b>–<b>c1</b>) The morphologies of nanoparticles; the red color represents the nanoparticles. (<b>d</b>–<b>f</b>) The morphologies of ABA star polymer without nanoparticles confined in a sphere with soft inner surface; the blue color represents the A blocks and the brushes, the red color represents the B blocks. (<b>g</b>–<b>i</b>) The morphologies of the mixture of ABA star polymers and nanoparticles confined in a hard sphere. the blue color represents the A blocks and the brushes, the red color represents the B blocks. The left column represents <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math>; the middle column represents <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.2</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.6</mn> </mrow> </semantics></math>; the right column represents <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.3</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.4</mn> </mrow> </semantics></math>.</p> Full article ">Figure 4
<p>The morphologies of ABA star polymer and nanoparticles with increasing the volume fraction of nanoparticle <math display="inline"><semantics> <msub> <mi>f</mi> <mi>p</mi> </msub> </semantics></math> for nanoparticle radius <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mi>p</mi> </msub> <mo>/</mo> <msub> <mi>R</mi> <mi>g</mi> </msub> <mo>=</mo> <mn>0.75</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math>. (<b>a</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.13</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.15</mn> </mrow> </semantics></math>, (<b>c</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.19</mn> </mrow> </semantics></math>, (<b>d</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.24</mn> </mrow> </semantics></math>, (<b>e</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.25</mn> </mrow> </semantics></math>, (<b>f</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.28</mn> </mrow> </semantics></math>. The blue color represents the A blocks and the brushes, the red color represents the B blocks.</p> Full article ">Figure 5
<p>(<b>a</b>) The entropy of the nanoparticles, <math display="inline"><semantics> <mrow> <mi>S</mi> <mo>/</mo> <msub> <mi>k</mi> <mi>B</mi> </msub> </mrow> </semantics></math>, as a function of the volume fraction of nanoparticles, <math display="inline"><semantics> <msub> <mi>f</mi> <mi>p</mi> </msub> </semantics></math>, when <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math>; (<b>b</b>) The steric packing interaction of the nanoparticles, <math display="inline"><semantics> <mrow> <msub> <mi>F</mi> <mrow> <mi>s</mi> <mi>t</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>K</mi> <mi>B</mi> </msub> <mi>T</mi> </mrow> </semantics></math>, as a function of the volume fraction of nanoparticles, <math display="inline"><semantics> <msub> <mi>f</mi> <mi>p</mi> </msub> </semantics></math>, when <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math>; (<b>c</b>) Nanoparticles density distributions along the perpendicular line through the center of the sphere with <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math>, the green, red and blue colors represent <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.15</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.24</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.28</mn> </mrow> </semantics></math>, respectively.</p> Full article ">Figure 6
<p>The regions of different morphologies of ABA star polymer and nanoparticles mixtures as a function of the nanoparticle radius for <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.15</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math>. The blue color represents the A blocks and the brushes, the red color represents the B blocks.</p> Full article ">Figure 7
<p>The phase diagram of the mixture of the ABA star polymer and nanoparticles as a function of the nanoparticle volume fraction <math display="inline"><semantics> <msub> <mi>f</mi> <mi>p</mi> </msub> </semantics></math> and the nanoparticle radius <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mi>p</mi> </msub> <mo>/</mo> <msub> <mi>R</mi> <mi>g</mi> </msub> </mrow> </semantics></math> with <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math>, the righttriangle, circle, uptriangle, diamond, square, lefttriangle, downtriangle and star represent the phase separation of the mixture, cylinder <math display="inline"><semantics> <msub> <mi>C</mi> <mrow> <mn>1</mn> <mo>−</mo> <mn>6</mn> <mo>−</mo> <mn>11</mn> </mrow> </msub> </semantics></math>, cylinder <math display="inline"><semantics> <msub> <mi>C</mi> <mrow> <mn>4</mn> <mo>−</mo> <mn>10</mn> </mrow> </msub> </semantics></math>, mixture of cylinders and lamellae <math display="inline"><semantics> <mrow> <msub> <mi>C</mi> <mrow> <mn>1</mn> <mo>−</mo> <mn>6</mn> </mrow> </msub> <mi>L</mi> </mrow> </semantics></math>, cylinder <math display="inline"><semantics> <msub> <mi>C</mi> <mrow> <mn>4</mn> <mo>−</mo> <mn>9</mn> </mrow> </msub> </semantics></math>, mixture of cylinders and lamellae <math display="inline"><semantics> <mrow> <mi>C</mi> <msub> <mi>L</mi> <mn>2</mn> </msub> </mrow> </semantics></math>, mixture of cylinders and multiple-continuous phases <math display="inline"><semantics> <mrow> <mi>C</mi> <mo>+</mo> <mi>M</mi> </mrow> </semantics></math> and multiple-continuous phases <span class="html-italic">M</span>, respectively.</p> Full article ">Figure 8
<p>The morphologies of the nanoparticles as a function of the volume fraction of each block when we allow nanoparticles to interact with both A blocks and homopolymer brushes. (<b>a</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.18</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.64</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.3</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.4</mn> </mrow> </semantics></math>, (<b>c</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.33</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.34</mn> </mrow> </semantics></math>, (<b>d</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.41</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.18</mn> </mrow> </semantics></math>. The blue color represents the A blocks and the brushes, the red color represents the nanoparticles.</p> Full article ">Figure 9
<p>The morphologies of the nanoparticles with increasing the nanoparticle volume fraction <math display="inline"><semantics> <msub> <mi>f</mi> <mi>p</mi> </msub> </semantics></math> for nanoparticle radius <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mi>p</mi> </msub> <mo>/</mo> <msub> <mi>R</mi> <mi>g</mi> </msub> <mo>=</mo> <mn>0.75</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.3</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.4</mn> </mrow> </semantics></math>. (<b>a</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.15</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.20</mn> </mrow> </semantics></math>, (<b>c</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.23</mn> </mrow> </semantics></math>, (<b>d</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.28</mn> </mrow> </semantics></math>. The blue color represents the A blocks and the brushes, the red color represents the nanoparticles.</p> Full article ">Figure 10
<p>(<b>a</b>) The entropy of the nanoparticles, <math display="inline"><semantics> <mrow> <mi>S</mi> <mo>/</mo> <msub> <mi>k</mi> <mi>B</mi> </msub> </mrow> </semantics></math>, as a function of the nanoparticles volume fraction <math display="inline"><semantics> <msub> <mi>f</mi> <mi>p</mi> </msub> </semantics></math>, when <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math>; (<b>b</b>) The steric packing interaction of the nanoparticles, <math display="inline"><semantics> <mrow> <msub> <mi>F</mi> <mrow> <mi>s</mi> <mi>t</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>K</mi> <mi>B</mi> </msub> <mi>T</mi> </mrow> </semantics></math>, as a function of the nanoparticles volume fraction <math display="inline"><semantics> <msub> <mi>f</mi> <mi>p</mi> </msub> </semantics></math>, when <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.3</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.4</mn> </mrow> </semantics></math>; (<b>c</b>) Nanoparticles density distributions along the perpendicular line through the center of the sphere with <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.3</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.4</mn> </mrow> </semantics></math>, the green, red and blue colors represent <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.15</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.20</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.23</mn> </mrow> </semantics></math>, respectively.</p> Full article ">Figure 11
<p>The regions of different morphologies of ABA star polymers and nanoparticles as a function of the nanoparticles radius with <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.15</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.3</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.4</mn> </mrow> </semantics></math>. The blue color represents the A blocks and the brushes, the red color represents the B blocks.</p> Full article ">Figure 12
<p>The phase diagram of the mixture of ABA star polymers and nanoparticles as a function of the nanoparticles volume fraction <math display="inline"><semantics> <msub> <mi>f</mi> <mi>p</mi> </msub> </semantics></math> and the nanoparticle radius <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mi>p</mi> </msub> <mo>/</mo> <msub> <mi>R</mi> <mi>g</mi> </msub> </mrow> </semantics></math> with <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.3</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.4</mn> </mrow> </semantics></math>, the lefttriangle, downtriangle, uptriangle, and star represent the cylindrical structurea, concentric lamellaes <math display="inline"><semantics> <msub> <mi>L</mi> <mn>3</mn> </msub> </semantics></math>, mixture of cylinders and lamellae <math display="inline"><semantics> <mrow> <mi>C</mi> <msub> <mi>L</mi> <mn>3</mn> </msub> </mrow> </semantics></math> and multiple-continuous phases <span class="html-italic">M</span>, respectively.</p> Full article ">Figure 13
<p>(<b>a</b>) The morphologies observed in the mixture of ABA star polymers and nanoparticles with <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msub> <mi>f</mi> <mrow> <mi>a</mi> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>0.13</mn> <mo>,</mo> <msub> <mi>f</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0.74</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0.15</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mi>p</mi> </msub> <mo>/</mo> <msub> <mi>R</mi> <mi>g</mi> </msub> <mo>=</mo> <mn>0.75</mn> </mrow> </semantics></math> and the interaction between the nanoparticles and the B blocks, under the spherical confinement with varying the radius of sphere; (<b>b</b>) The phase sequence of morphologies as a function of <math display="inline"><semantics> <mrow> <mi>R</mi> <mo>/</mo> <msub> <mi>R</mi> <mi>g</mi> </msub> </mrow> </semantics></math>. The blue color represents the A blocks and the brushes, the red color represents the B blocks.</p> Full article ">
12 pages, 1447 KiB  
Article
Inhibition of Carrageenan-Induced Acute Inflammation in Mice by the Microgramma vacciniifolia Frond Lectin (MvFL)
by Leydianne Leite de Siqueira Patriota, Dalila de Brito Marques Ramos, Mariana Gama e Silva, Angela Caroline Lima Amorim dos Santos, Yasmym Araújo Silva, Patrícia Maria Guedes Paiva, Emmanuel Viana Pontual, Lidiane Pereira de Albuquerque, Rosemairy Luciane Mendes and Thiago Henrique Napoleão
Polymers 2022, 14(8), 1609; https://doi.org/10.3390/polym14081609 - 15 Apr 2022
Cited by 13 | Viewed by 3681
Abstract
Most anti-inflammatory drugs used nowadays have an excessive cost and their prolonged use has been connected with several injurious effects. Thus, the search for new anti-inflammatory agents is increasing. Lectins are carbohydrate-interacting proteins that can modulate immune response and the release of inflammation [...] Read more.
Most anti-inflammatory drugs used nowadays have an excessive cost and their prolonged use has been connected with several injurious effects. Thus, the search for new anti-inflammatory agents is increasing. Lectins are carbohydrate-interacting proteins that can modulate immune response and the release of inflammation mediators. The Microgramma vacciniifolia frond lectin (MvFL) was previously reported to be an immunomodulatory agent in vitro. This work aimed to evaluate the effects of MvFL on the in vivo inflammatory status in the carrageenan-induced peritonitis and paw edema, using female Swiss mice. The animals were pretreated intraperitoneally with MvFL (5 and 10 mg/kg). In the peritonitis assay, the total and differential migration of white blood cells was evaluated, as well as the levels of cytokines, nitric oxide (NO), and total proteins in the peritoneal fluid. In the paw edema evaluation, the paw volume was measured in the early (from 30 min–2 h) and late (3–4 h) phases of edema formation. MvFL (5 and 10 mg/kg) was efficient in reducing neutrophil infiltration, pro-inflammatory cytokines (IL-6, IL-17, and TNF-α), NO, and protein content in the peritoneal fluid. It also repressed the edema formation in the late phase of the assay. In conclusion, MvFL showed inhibitory effects in in vivo acute inflammation, which encouraged future studies exploiting its immunomodulatory ability. Full article
(This article belongs to the Special Issue Characterization, Bioactivities and Biotechnological Applications of Proteins and Peptides)
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Figure 1

Figure 1
<p>Graphical representation of the study design. The effects of MvFL on inflammatory status in the carrageenan-induced peritonitis and paw edema were investigated in Swiss mice. The animals were pretreated intraperitoneally with MvFL. In the peritonitis assay, the total and differential migration of the leukocytes were evaluated, as well as the total protein, cytokines, and nitric oxide (NO) levels in the peritoneal fluid. The inset (<b>1</b>) schematizes the recruitment of leukocytes to the area of inflammation. In the paw edema assay, the volume of the paw was measured in the early (30 min–2 h) and late (3–4 h) phases of edema formation. The inset (<b>2</b>) shows the edema formation process with extravasation of the plasma proteins followed by movement of the fluid from the intravascular to the interstitial space.</p> Full article ">Figure 2
<p>Effects of MvFL (5 and 10 mg/kg) and dexamethasone (2 mg/kg) on leukocyte migration in the peritoneal cavity of mice submitted to carrageenan-induced peritonitis. The graphs show the number of leukocytes per mL (<b>a</b>) and the percentage of neutrophils (<b>b</b>) and mononucleated cells (<b>c</b>) among them. Values are expressed as mean ± standard error of the mean (<span class="html-italic">n</span> = 6). Different letters above the bars indicate significant (<span class="html-italic">p</span> &lt; 0.05) differences between treatments according to ANOVA followed by Tukey’s test.</p> Full article ">Figure 3
<p>Cytokine (<b>a</b>–<b>g</b>) and nitrite (<b>h</b>) concentrations in the peritoneal fluid of mice submitted to carrageenan-induced peritonitis after pre-treatment with MvFL (5 and 10 mg/kg) or dexamethasone (2 mg/kg). Values are expressed as mean ± standard error of the mean (<span class="html-italic">n</span> = 6). Different letters above the bars indicate significant (<span class="html-italic">p</span> &lt; 0.05) differences between treatments according to ANOVA followed by Tukey’s test.</p> Full article ">Figure 4
<p>Total protein concentration in the peritoneal liquid from mice submitted to carrageenan-promoted peritonitis after pre-treatment with MvFL (5 and 10 mg/kg) or dexamethasone (2 mg/kg). Values are expressed as mean ± standard error of the mean (<span class="html-italic">n</span> = 6). Different letters indicate significant (<span class="html-italic">p</span> &lt; 0.05) differences between treatments according to ANOVA followed by Tukey’s test.</p> Full article ">Figure 5
<p>Anti-inflammatory effect of MvFL (5 and 10 mg/kg) and indomethacin (20 mg/kg) on carrageenan-promoted paw edema. Values are expressed as mean ± standard error of the mean (<span class="html-italic">n</span> = 6). Different letters indicate significant (<span class="html-italic">p</span> &lt; 0.05) differences between treatments according to ANOVA followed by Tukey’s test.</p> Full article ">
15 pages, 1678 KiB  
Review
Microneedles in Action: Microneedling and Microneedles-Assisted Transdermal Delivery
by Dong-Jin Lim and Hong-Jun Kim
Polymers 2022, 14(8), 1608; https://doi.org/10.3390/polym14081608 - 15 Apr 2022
Cited by 31 | Viewed by 6285
Abstract
Human skin is a multilayered physiochemical barrier protecting the human body. The stratum corneum (SC) is the outermost keratinized layer of skin through which only molecules with less or equal to 500 Da (Dalton) in size can freely move through the skin. Unfortunately, [...] Read more.
Human skin is a multilayered physiochemical barrier protecting the human body. The stratum corneum (SC) is the outermost keratinized layer of skin through which only molecules with less or equal to 500 Da (Dalton) in size can freely move through the skin. Unfortunately, the conventional use of a hypothermic needle for large therapeutic agents is susceptible to needle phobia and the risk of acquiring infectious diseases. As a new approach, a microneedle (MN) can deliver therapeutically significant molecules without apparent limitations associated with its molecular size. Microneedles can create microchannels through the skin’s SC without stimulating the proprioceptive pain nerves. With recent technological advancements in both fabrication and drug loading, MN has become a versatile platform that improves the efficacy of transdermally applied therapeutic agents (TAs) and associated treatments for various indications. This review summarizes advanced fabrication techniques for MN and addresses numerous TA coating and TA elution strategies from MN, offering a comprehensive perspective on the current microneedle technology. Lastly, we discuss how microneedling and microneedle technologies can improve the clinical efficacy of a variety of skin diseases. Full article
(This article belongs to the Special Issue Nanomaterials Template for Organic or Composite Polymers in Biomedical Application)
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Figure 1

Figure 1
<p>Types of microneedles used for transdermal drug delivery. (<b>a</b>) solid microneedles ionically etched from silicon wafer, (<b>b</b>) solid microneedles laser cut from stainless steel, (<b>c</b>) solid microneedles acid-etched from titanium sheet, (<b>d</b>) solid microneedles chemically etched from silicon wafers, and (<b>e</b>) hollow microneedles formed by electrodeposition of metal on to a polymer. Reproduced with permission from [<a href="#B18-polymers-14-01608" class="html-bibr">18</a>], copyright Elsevier 2004.</p> Full article ">Figure 2
<p>Different types of microneedles (<b>a</b>) solid microneedles use poke with patch approach, are used for pre-treatment of the skin; (<b>b</b>) coated microneedles use a coat and poke approach, a coating of drug solution is applied on the needle surface; (<b>c</b>) dissolving microneedles are made of biodegradable polymers; (<b>d</b>) hollow microneedles are filled with the drug solution and deposit the drug in the dermis. Reproduced with permission from [<a href="#B23-polymers-14-01608" class="html-bibr">23</a>], copyright Elsevier 2019.</p> Full article ">Figure 3
<p>(<b>a</b>) Fabrication process of MNs. (<b>b</b>) SEM images of LCC-NP-coated MNs. (<b>c</b>) magnified SEM images of the MNs within the red box of (<b>b</b>). (<b>d</b>) fluorescence microscope image. (<b>e</b>) confocal image of NBD PE-labeled NP-coated MNs. (<b>f</b>) photograph of MN patch pressed into porcine skin. (<b>g</b>) SEM images of dissolved MN after inserting into the skin. (<b>h</b>) magnified SEM image of MNs in the red box of (<b>g</b>). (<b>i</b>) confocal image of porcine skin after treatment with NBD PE-labeled MNs. Reproduced with permission from [<a href="#B83-polymers-14-01608" class="html-bibr">83</a>]. Copyright American Chemical Society 2018.</p> Full article ">Figure 4
<p>Schematic of the microneedle-assisted transdermal delivery of aPD1 for skin cancer treatment. (<b>a</b>) Schematic of the aPD1 delivered by an MN patch loaded with physiologically self-dissociated NPs. With GOx/CAT enzymatic system immobilized inside the NPs by double-emulsion method, the enzyme-mediated conversion of blood glucose to gluconic acid promotes the sustained dissociation of NPs, subsequently leading to the release of aPD1. (<b>b</b>) The blockade of PD-1 by aPD1 activates the immune system to destroy skin cancer cells. Reproduced from [<a href="#B92-polymers-14-01608" class="html-bibr">92</a>].</p> Full article ">
19 pages, 8555 KiB  
Article
Development of an Online Quality Control System for Injection Molding Process
by Ming-Hong Tsai, Jia-Chen Fan-Jiang, Guan-Yan Liou, Feng-Jung Cheng, Sheng-Jye Hwang, Hsin-Shu Peng and Hsiao-Yeh Chu
Polymers 2022, 14(8), 1607; https://doi.org/10.3390/polym14081607 - 15 Apr 2022
Cited by 9 | Viewed by 3485
Abstract
This research developed an adaptive control system for injection molding process. The purpose of this control system is to adaptively maintain the consistency of product quality by minimize the mass variation of injection molded parts. The adaptive control system works with the information [...] Read more.
This research developed an adaptive control system for injection molding process. The purpose of this control system is to adaptively maintain the consistency of product quality by minimize the mass variation of injection molded parts. The adaptive control system works with the information collected through two sensors installed in the machine only—the injection nozzle pressure sensor and the temperature sensor. In this research, preliminary experiments are purposed to find master pressure curve that relates to product quality. Viscosity index, peak pressure, and timing of the peak pressure are used to characterize the pressure curve. The correlation between product quality and parameters such as switchover position and injection speed were used to produce a training data for back propagation neural network (BPNN) to compute weight and bias which are applied on the adaptive control system. By using this system, the variation of part weight is maintained to be as low as 0.14%. Full article
(This article belongs to the Special Issue Recent Advances in Polymer Rheology)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Flow chart of injection molding process.</p> Full article ">Figure 2
<p>P-V-T Relationship of Polypropylene (PP).</p> Full article ">Figure 3
<p>Pressure curve characteristics.</p> Full article ">Figure 4
<p>Neural Network Prediction Model.</p> Full article ">Figure 5
<p>The mold of the thin plastic disk sample.</p> Full article ">Figure 6
<p>The size of the thin plastic disk sample.</p> Full article ">Figure 7
<p>The establishment process of BPNN model.</p> Full article ">Figure 8
<p>Flowchart of adaptive control strategy.</p> Full article ">Figure 9
<p>Relationship between viscosity index and switchover position.</p> Full article ">Figure 10
<p>Relationship between peak pressure and switchover position.</p> Full article ">Figure 11
<p>Relationship between timing of peak pressure and switchover position.</p> Full article ">Figure 12
<p>Relationship between part weight and switchover position.</p> Full article ">Figure 13
<p>Relationship between viscosity index and injection speed.</p> Full article ">Figure 14
<p>Relationship between peak pressure and injection speed.</p> Full article ">Figure 15
<p>Relationship between timing of peak pressure and injection speed.</p> Full article ">Figure 16
<p>Relationship between part weight and injection speed.</p> Full article ">Figure 17
<p>Prediction results of viscosity index.</p> Full article ">Figure 18
<p>Prediction results of peak pressure.</p> Full article ">Figure 19
<p>Prediction results of timing of peak pressure.</p> Full article ">Figure 20
<p>Adaptively adjust parameters results by adaptive control system.</p> Full article ">Figure 21
<p>Distribution of viscosity index in experiment.</p> Full article ">Figure 22
<p>Distribution of peak pressure in experiment.</p> Full article ">Figure 23
<p>Distribution of timing of peak pressure in experiment.</p> Full article ">Figure 24
<p>Distribution of part weight in experiment.</p> Full article ">Figure 25
<p>Performance comparison between using system and no system.</p> Full article ">
19 pages, 8529 KiB  
Article
Multiscale Thermal Investigations of Graphite Doped Polystyrene Thermal Insulation
by Ákos Lakatos and Attila Csík
Polymers 2022, 14(8), 1606; https://doi.org/10.3390/polym14081606 - 14 Apr 2022
Cited by 14 | Viewed by 3051
Abstract
Nowadays, to improve quality of life, to have a more comfortable life, in internal spaces we try to maintain conditions that are free from external environmental influences. Thus, existing as well as newly built houses have adequate interiors maintaining their temperature, warming, or [...] Read more.
Nowadays, to improve quality of life, to have a more comfortable life, in internal spaces we try to maintain conditions that are free from external environmental influences. Thus, existing as well as newly built houses have adequate interiors maintaining their temperature, warming, or cooling due to the environment compensation. One way to create this is to reduce the heat loss in buildings. An option to achieve this is the application of thermal insulations. Nowadays, the use of super insulation materials such as aerogel and vacuum insulation panels and other nano-structured insulations, such as graphite doped expanded polystyrene, is becoming increasingly justified. These are relatively new materials, and we know only a little about them. This paper presents research results based on temperature-induced investigations of nanostructured graphite expanded polystyrene, to reveal its thermal stability after long-term and short-term thermal annealing, simulating the ageing of the material. Firstly, with a differential scanning calorimeter, we will explore the thermal stability profile of the specimens. After this, the paper will present temperature-induced changes in both the thermal properties and the structure of the samples. We will also present changes in the thermal conductivity, modifications in the surface, and compressive property variation induced by thermal annealing. The samples were thermal annealed at 70 °C for 6 weeks, at 100 and 110 °C for 1 h. Besides the thermal conductivity measurements with Netzsch 446 heat flow meter equipment, we will present specific heat capacity measurement results executed with the same equipment. Moreover, sorption isotherms of the as-received and annealed samples were registered and completed with hydrophobic experiments, too. Furthermore, from the measurements, we showed that temperature should affect a significant change in the thermal conductivity of materials. Moreover, the changes in the graphite expanded polystyrene before and after thermal annealing were investigated by Scanning Electron Microscopy, as well as optical microscopy. The structural changes were further followed by an X-ray diffractometer and the IR absorption capability was tested, too. Full article
(This article belongs to the Special Issue Application of Polymeric Materials in the Building Industry)
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Figure 1
<p>The heat transfer inside the graphite EPS.</p> Full article ">Figure 2
<p>The measurement results of the graphite EPS samples with the DSC equipment.</p> Full article ">Figure 3
<p>(<b>a</b>) Photo images from the samples (from left to right: As received, annealed at 70 °C, annealed at 100 °C and annealed at 110 °C). (<b>b</b>) Optical microscope images from the samples. (<b>c</b>) Scanning Electron microscope images from the samples.</p> Full article ">Figure 3 Cont.
<p>(<b>a</b>) Photo images from the samples (from left to right: As received, annealed at 70 °C, annealed at 100 °C and annealed at 110 °C). (<b>b</b>) Optical microscope images from the samples. (<b>c</b>) Scanning Electron microscope images from the samples.</p> Full article ">Figure 4
<p>The results of the beads analysis with the box chart method.</p> Full article ">Figure 5
<p>The results of the beads analysis with box chart method.</p> Full article ">Figure 6
<p>(<b>a</b>) Thermal conductivities of the samples in the function of the mean temperature. (<b>b</b>) The thermal conductivities in the function of the applied load.</p> Full article ">Figure 6 Cont.
<p>(<b>a</b>) Thermal conductivities of the samples in the function of the mean temperature. (<b>b</b>) The thermal conductivities in the function of the applied load.</p> Full article ">Figure 7
<p>The changes in the thickness in the function of the applied load.</p> Full article ">Figure 8
<p>The specific heat capacities of the samples at 25 °C.</p> Full article ">Figure 9
<p>The sorption isotherms.</p> Full article ">Figure 10
<p>The hydrophobic test.</p> Full article ">Figure 11
<p>The X-ray diffractometer results.</p> Full article ">Figure 12
<p>IR absorption test.</p> Full article ">
17 pages, 4810 KiB  
Article
Polymer Composites Based on Glycol-Modified Poly(Ethylene Terephthalate) Applied to Additive Manufacturing Using Melted and Extruded Manufacturing Technology
by Katarzyna Bulanda, Mariusz Oleksy and Rafał Oliwa
Polymers 2022, 14(8), 1605; https://doi.org/10.3390/polym14081605 - 14 Apr 2022
Cited by 6 | Viewed by 2707
Abstract
As part of the work, innovative polymer composites dedicated to 3D printing applications were developed. For this purpose, the influence of modified fillers, such as silica modified with alumina, bentonite modified with quaternary ammonium salt, and hybrid filler lignin/silicon dioxide, on the functional [...] Read more.
As part of the work, innovative polymer composites dedicated to 3D printing applications were developed. For this purpose, the influence of modified fillers, such as silica modified with alumina, bentonite modified with quaternary ammonium salt, and hybrid filler lignin/silicon dioxide, on the functional properties of composites based on glycol-modified poly(ethylene terephthalate) (PET-G) was investigated. In the first part of the work, using the proprietary technological line, filaments from unfilled polymer and its composites were obtained, which contained modified fillers in an amount from 1.5% to 3.0% by weight. The fittings for the testing of functional properties were obtained using the 3D printing technique in the Melted and Extruded Manufacturing (MEM) technology and the injection molding technique. In a later part of the work, rheological properties such as mass melt flow rate (MFR) and viscosity, and mechanical properties such as Rockwell hardness, Charpy impact strength, and static tensile strength with Young’s modulus were presented. The structure of the obtained composites was also described and determined using scanning electron microscopy with an attachment for the microanalysis of chemical composition (SEM/EDS) and the atomic force microscope (AFM). The correct dispersion of the fillers in the polymer matrix was confirmed by wide-angle X-ray scattering analysis (WAXS). In turn, the physicochemical properties were presented on the basis of the research results: thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR). On the basis of the obtained results, it was found that both the amount and the type of fillers used significantly affected the functional properties of the tested composites. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Structure of Polymer Nanomaterials)
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Graphical abstract
Full article ">Figure 1
<p>Proprietary technological line for filament production: (<b>a</b>) view of a single-screw extruder with a hopper, (<b>b</b>) view of an air-cooled roller extractor with a control panel, (<b>c</b>) filament extraction speed sensor system, (<b>d</b>) filament diameter measurement section, and (<b>e</b>) winder with control panel.</p> Full article ">Figure 2
<p>The dimensions of the samples: (<b>a</b>) a bar and (<b>b</b>) a paddle.</p> Full article ">Figure 3
<p>Viscosity curves of PET-G polymer and composites based on PET-G.</p> Full article ">Figure 4
<p>Hardness test results of (<b>a</b>) samples obtained by 3D printing and (<b>b</b>) samples obtained by injection molding.</p> Full article ">Figure 5
<p>Impact strength test results of (<b>a</b>) samples obtained by 3D printing and (<b>b</b>) samples obtained by injection molding.</p> Full article ">Figure 6
<p>AFM images showing topographies for: (<b>a</b>) PET-G, (<b>c</b>) PET-G/3%S, (<b>e</b>) PET-G/3%B, (<b>g</b>) PET-G/3% L, and (<b>i</b>) PET-G/1,5%L/1.5%B; and phase images for: (<b>b</b>) PET-G, (<b>d</b>) PET-G/3%S, (<b>f</b>) PET-G/3%B, (<b>h</b>) PET-G/3%L, and (<b>j</b>) PET-G/1.5%L/1.5%B.</p> Full article ">Figure 6 Cont.
<p>AFM images showing topographies for: (<b>a</b>) PET-G, (<b>c</b>) PET-G/3%S, (<b>e</b>) PET-G/3%B, (<b>g</b>) PET-G/3% L, and (<b>i</b>) PET-G/1,5%L/1.5%B; and phase images for: (<b>b</b>) PET-G, (<b>d</b>) PET-G/3%S, (<b>f</b>) PET-G/3%B, (<b>h</b>) PET-G/3%L, and (<b>j</b>) PET-G/1.5%L/1.5%B.</p> Full article ">Figure 7
<p>SEM micrographs with an EDS attachment of PET-G polymer and composites based on PET-G: (<b>a</b>) PET-G, (<b>b</b>) PET-G/3%S, (<b>c</b>) PET-G/3%B, (<b>d</b>) PET-G/3%L, and (<b>e</b>) PET-G/1.5%L/1.5%B. The red contour marks the area subjected to EDS analysis, which was performed in order to observe the degree of filler dispersion and the distribution of the silicon element.</p> Full article ">Figure 7 Cont.
<p>SEM micrographs with an EDS attachment of PET-G polymer and composites based on PET-G: (<b>a</b>) PET-G, (<b>b</b>) PET-G/3%S, (<b>c</b>) PET-G/3%B, (<b>d</b>) PET-G/3%L, and (<b>e</b>) PET-G/1.5%L/1.5%B. The red contour marks the area subjected to EDS analysis, which was performed in order to observe the degree of filler dispersion and the distribution of the silicon element.</p> Full article ">Figure 8
<p>Results of DTG analysis (mass change derivative curve) of PET-G polymer and composites based on PET-G.</p> Full article ">Figure 9
<p>Results of the differential scanning calorimetry (DSC) analysis of PET-G and PET-G composites.</p> Full article ">Figure 10
<p>WAXS patterns: (<b>a</b>) fillers; (<b>b</b>) PET-G and composites with the addition of modified S, B, and L fillers.</p> Full article ">Figure 11
<p>FT-IR spectra recorded for the composition.</p> Full article ">
44 pages, 2783 KiB  
Review
Pervaporation as a Successful Tool in the Treatment of Industrial Liquid Mixtures
by Kadavil Subhash Lakshmy, Devika Lal, Anandu Nair, Allan Babu, Haritha Das, Neethu Govind, Mariia Dmitrenko, Anna Kuzminova, Aleksandra Korniak, Anastasia Penkova, Abhimanyu Tharayil and Sabu Thomas
Polymers 2022, 14(8), 1604; https://doi.org/10.3390/polym14081604 - 14 Apr 2022
Cited by 19 | Viewed by 5864
Abstract
Pervaporation is one of the most active topics in membrane research, and it has time and again proven to be an essential component for chemical separation. It has been employed in the removal of impurities from raw materials, separation of products and by-products [...] Read more.
Pervaporation is one of the most active topics in membrane research, and it has time and again proven to be an essential component for chemical separation. It has been employed in the removal of impurities from raw materials, separation of products and by-products after reaction, and separation of pollutants from water. Given the global problem of water pollution, this approach is efficient in removing hazardous substances from water bodies. Conventional processes are based on thermodynamic equilibria involving a phase transition such as distillation and liquid–liquid extraction. These techniques have a relatively low efficacy and nowadays they are not recommended because it is not sustainable in terms of energy consumption and/or waste generation. Pervaporation emerged in the 1980s and is now becoming a popular membrane separation technology because of its intrinsic features such as low energy requirements, cheap separation costs, and good quality product output. The focus of this review is on current developments in pervaporation, mass transport in membranes, material selection, fabrication and characterization techniques, and applications of various membranes in the separation of chemicals from water. Full article
(This article belongs to the Special Issue Advanced Polymeric Materials for Membrane Technology II)
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<p>Classification of mechanisms of mass transport.</p> Full article ">Figure 2
<p>Models used for mass transfer in pervaporation.</p> Full article ">Figure 3
<p>Three cases of possible changes of MMMs transport parameters depending on the modifier.</p> Full article ">Figure 4
<p>Classification of membranes.</p> Full article ">Figure 5
<p>Commonly used fabrication techniques.</p> Full article ">Figure 6
<p>Schematic of the preparation of GO-PI hollow fiber membranes by direct spinning. Reprinted with permission from Ref. [<a href="#B274-polymers-14-01604" class="html-bibr">274</a>]. Copyright 2018 Aisheng Huang et al.</p> Full article ">Figure 7
<p>Preparation of PA-GO composite membranes via pressure-assisted ultrafiltration with subsequent interfacial polymerization. Reprinted with permission from Ref. [<a href="#B279-polymers-14-01604" class="html-bibr">279</a>]. Copyright 2020 Liu X. et al.</p> Full article ">Figure 8
<p>SEM surface images of (<b>a</b>) CTA pristine, (<b>b</b>) CTA-1 wt.% SiO<sub>2</sub>, (<b>c</b>) CTA-2 wt.% SiO<sub>2</sub>, (<b>d</b>) CTA-3 wt.% SiO<sub>2</sub>, (<b>e</b>) CTA4 wt.% SiO<sub>2</sub> membranes, SEM cross-sectional images of (<b>f</b>) CTA pristine, (<b>g</b>) CTA-1 wt.% SiO<sub>2</sub>, (<b>h</b>) CTA-2 wt.% SiO<sub>2</sub>, (<b>i</b>) CTA-3 wt.% SiO<sub>2</sub>, and (<b>j</b>) CTA-4 wt.% SiO<sub>2</sub> of membranes. Reprinted with permission from Ref. [<a href="#B286-polymers-14-01604" class="html-bibr">286</a>]. Copyright 2020 Prihatiningtyas I. et al.</p> Full article ">Figure 9
<p>Classification of organic–organic mixtures.</p> Full article ">Figure 10
<p>Desalination using pervaporation.</p> Full article ">
14 pages, 1596 KiB  
Article
Effectiveness and Applications of a Metal-Coated HNT/Polylactic Acid Antimicrobial Filtration System
by Antwine W. McFarland, Jr., Anusha Elumalai, Christopher C. Miller, Ahmed Humayun and David K. Mills
Polymers 2022, 14(8), 1603; https://doi.org/10.3390/polym14081603 - 14 Apr 2022
Cited by 11 | Viewed by 2972
Abstract
A broad-spectrum antimicrobial respiration apparatus designed to fight bacteria, viruses, fungi, and other biological agents is critical in halting the current pandemic’s trajectory and containing future outbreaks. We applied a simple and effective electrodeposition method for metal (copper, silver, and zinc) coating the [...] Read more.
A broad-spectrum antimicrobial respiration apparatus designed to fight bacteria, viruses, fungi, and other biological agents is critical in halting the current pandemic’s trajectory and containing future outbreaks. We applied a simple and effective electrodeposition method for metal (copper, silver, and zinc) coating the surface of halloysite nanotubes (HNTs). These nanoparticles are known to possess potent antiviral and antimicrobial properties. Metal-coated HNTs (mHNTs) were then added to polylactic acid (PLA) and extruded to form an mHNT/PLA 3D composite printer filament. Our composite 3D printer filament was then used to fabricate an N95-style mask with an interchangeable/replaceable filter with surfaces designed to inactivate a virus and kill bacteria on contact, thus reducing deadly infections. The filter, made of a multilayered antimicrobial/mHNT blow spun polymer and fabric, is disposable, while the mask can be sanitized and reused. We used several in vitro means of assessing critical clinical features and assessed the bacterial growth inhibition against commonly encountered bacterial strains. These tests demonstrated the capability of our antimicrobial filament to fabricate N95 masks and filters that possessed antibacterial capabilities against both Gram-negative and Gram-positive bacteria. Full article
(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)
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Graphical abstract
Full article ">Figure 1
<p>PLA beads coated with mHNTs in Mueller-Hinton broth for 48 h with <span class="html-italic">E. coli</span> (<b>A</b>) or <span class="html-italic">S. aureus</span> (<b>B</b>). Optical density was taken at 630 nm wavelength. Error bars represent ± standard deviation. Asterisk (*) indicates a significant difference (<span class="html-italic">p</span> &lt; 0.05) to control (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 2
<p>PLA beads coated with GS-doped mHNTs in Mueller–Hinton broth for 48 h with <span class="html-italic">E. coli</span>. Optical density readings were taken at 0, 24, and 48 h. Optical density was taken at 630 nm wavelength. Error bars represent ± standard deviation (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 3
<p>PLA beads coated with GS-doped mHNTs in Mueller–Hinton broth for 48 h with <span class="html-italic">S. aureus</span>. Optical density readings were taken at 0, 24, and 48 h. Optical density was taken at 630 nm wavelength. Error bars represent ± standard deviation (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 4
<p>Three-dimensional-printed PLA with GS-doped mHNTs in Mueller–Hinton broth for 48 h with <span class="html-italic">E. coli</span>. Optical density readings were taken at 0, 24, and 48 h post-inoculation. Optical density was taken at 630 nm wavelength. Error bars represent ± standard deviation (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 5
<p>Three-dimensional-printed PLA with GS-doped mHNTs in Mueller–Hinton broth for 48 h with <span class="html-italic">S. aureus</span>. Optical density readings were taken at 0, 24, and 48 h post-inoculation. Optical density was taken at 630 nm wavelength. Error bars represent ± standard deviation (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 6
<p>Mueller–Hinton agar plates, plated with <span class="html-italic">E. coli</span>, and (<b>A</b>) no sample, (<b>B</b>) PLA, (<b>C</b>) 3D-printed GS/Ag/HNT disc, (<b>D</b>) 3D-printed GS/Cu/HNT disc, (<b>E</b>) 3D-printed GS/Zn/HNT disc, and (<b>F</b>) 3D-printed GS/Ag, Cu, Zn/HNT disc.</p> Full article ">Figure 7
<p>Mueller–Hinton agar plates, plated with <span class="html-italic">S. aureus</span>, and (<b>A</b>) nothing, (<b>B</b>) PLA, (<b>C</b>) 3D-printed GS/Ag/HNT disc, (<b>D</b>) 3D-printed GS/Cu/HNT disc, (<b>E</b>) 3D-printed GS/Zn/HNT disc, and (<b>F</b>) 3D-printed GS/Ag, Cu, Zn/HNT disc.</p> Full article ">Figure 8
<p>Zone of inhibition diameter average for each respective 3D-printed disc after 24 h. These were GS-loaded mHNTs. Error bars represent ± standard deviation.</p> Full article ">Figure 9
<p>(<b>A</b>) Example of N95 masks and filter frameworks 3D printed with a customized Cu/HNT printer filament. (<b>B</b>,<b>C</b>) Zn/HNT filter blow spun on a 3D-printed Cu/HNT filter frame.</p> Full article ">Figure 10
<p>(<b>A</b>) Filter framework and blow spun ZnHNT fibers, (<b>B</b>) digital image of filter surface, (<b>C</b>) high-power view of ZnHNT fibers (ZnHNTs indicated by red arrow) and (<b>D</b>) filter composition.</p> Full article ">
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