Polymers

15 pages, 12714 KiB

Open AccessArticle

Effect of Adding Silver-Doped Carbon Nanotube Fillers to Heat-Cured Acrylic Denture Base on Impact Strength, Microhardness, and Antimicrobial Activity: A Preliminary Study

by Abdulaziz Alhotan, Rasha M. Abdelraouf, Sabry A. El-Korashy, Nawaf Labban, Hanan Alotaibi, Jukka P. Matinlinna and Tamer M. Hamdy

Polymers 2023, 15(13), 2976; https://doi.org/10.3390/polym15132976 - 7 Jul 2023

Cited by 4 | Viewed by 1907

Abstract

Poly (methyl methacrylate) (PMMA), is an acrylic polymer substance that is mostly used for denture base applications. The purpose of this laboratory study was to investigate the effect of adding 0.05 wt.% Ag-doped carbon nanotubes (CNT) to PMMA-based (PMMA and MMA) denture base [...] Read more.

Poly (methyl methacrylate) (PMMA), is an acrylic polymer substance that is mostly used for denture base applications. The purpose of this laboratory study was to investigate the effect of adding 0.05 wt.% Ag-doped carbon nanotubes (CNT) to PMMA-based (PMMA and MMA) denture base material on the impact strength, microhardness, and antimicrobial activity. A total of 60 heat-cured acrylic resin specimens were prepared. The specimens were randomly divided into two main groups (n = 30/group), according to the powder used: (a) control group, using heat-cured PMMA; (b) treatment group, using a powder prepared by blending 0.05 wt.% silver-doped CNT nanoparticles with heat-cured PMMA. The impact strength, microhardness and anticandidal activity for each group were assessed via the Charpy, Vickers and agar diffusion tests, respectively (n = 10/test for each subgroup). Data were analyzed using independent-sample t-tests (p ≤ 0.05). The results of the impact strength test revealed that the treated heat-cured PMMA-MMA with Ag-doped CNT (2.2 kJ/mm²) was significantly higher than that of the control heat-cured PMMA (1.6 kJ/mm²). Similarly, the Vickers microhardness of the treatment group (52.7 VHN) was significantly higher than that of the control group (19.4 VHN). Regarding the agar diffusion test, after 24 h of incubation, the treated heat-cured PMMA with the Ag-doped CNT exhibited significantly higher anticandidal activity than that of the control group. Therefore, Ag-doped carbon nanotubes could be considered as promising fillers for the dental heat-cured acrylic resin to improve the resistance of the resultant denture against sudden fractures, scratching, and candida invasion. Full article

(This article belongs to the Special Issue Polymers for Medical and Dental Applications)

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12 pages, 2608 KiB

Open AccessArticle

Synthesis and Characterization of an Environmentally Friendly Phenol–Formaldehyde Resin Modified with Waste Plant Protein

by Hanyin Li, Sen Wang, Xiang Zhang, Hao Wu, Yujie Wang, Na Zhou, Zijie Zhao, Chao Wang, Xiaofan Zhang, Xian Wang and Cheng Li

Polymers 2023, 15(13), 2975; https://doi.org/10.3390/polym15132975 - 7 Jul 2023

Cited by 8 | Viewed by 1866

Abstract

To develop a lower-cost, excellent-performance, and environmentally friendly phenol–formaldehyde (PF) resin, soybean meal was used to modify PF resin, and soybean meal–phenol–formaldehyde (SMPF) resins were prepared. This reveals the effect of soybean meal on the structural, bonding, and curing properties of PF resin, [...] Read more.

To develop a lower-cost, excellent-performance, and environmentally friendly phenol–formaldehyde (PF) resin, soybean meal was used to modify PF resin, and soybean meal–phenol–formaldehyde (SMPF) resins were prepared. This reveals the effect of soybean meal on the structural, bonding, and curing properties of PF resin, which are very important for its applications in the wood industry. The resins’ physicochemical properties and curing performance were investigated, showing that SMPF resins have higher curing temperatures than PF resin. The Fourier transform infrared spectroscopy results indicated that a cross-linking reaction occurred between the amino groups of soybean protein and the hydroxymethyl phenol. Moreover, with the addition of soybean meal, the viscosity of SMPF increased while the gel time decreased. It is worth mentioning that SMPF-2 resin has favorable viscosity, short gel time, low curing temperature (135.78 °C), and high water resistance and bonding strength (1.01 MPa). Finally, all the plywoods bonded with SMPF resins have good water resistance and bonding strength, which could meet the standard (GB/T 17657-2013, type I) for plywood. The optimized SMPF resins showed the potential for application to partially replace PF resin in the wood industry. Full article

(This article belongs to the Special Issue Resin-Based Polymer Materials and Related Applications)

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16 pages, 9826 KiB

Open AccessArticle

Controlling the Fiber Stress Distribution with Variable-Frequency Step Roll for Tunable Spun Yarn Structures

by Zhiyong Peng, Wei Li, Ze Chen, Pinxun Wang, Ziyi Su, Yue Sun, Keshuai Liu, Duo Xu and Weilin Xu

Polymers 2023, 15(13), 2974; https://doi.org/10.3390/polym15132974 - 7 Jul 2023

Viewed by 1632

Abstract

The dynamic regulation of fiber stress distribution in the yarn-forming triangle area is critical for controlling variable composite yarn structures, including siro and sirofil composite yarns. In this study, comparison analyses of the variable geometric structure and stress distribution during the yarn-forming process, [...] Read more.

The dynamic regulation of fiber stress distribution in the yarn-forming triangle area is critical for controlling variable composite yarn structures, including siro and sirofil composite yarns. In this study, comparison analyses of the variable geometric structure and stress distribution during the yarn-forming process, which involves step rolls with asymmetrical fiber control, have been carried out using ring-spinning technology. The geometric analyses show that partly staple fibers are continuously controlled while other fibers intermittently lack stress restraint, resulting in cyclically changed helical angles and wrapping density in the yarn-forming triangle area. The yarn structure model displayed that periodically distributed staple fibers occur in siro composite yarn, while sirofil composite yarn shows gradual periodic changes with uniform thickness variations, caused by cyclical changes in the stress distribution between filaments, and the strand altered the yarn-forming zone shapes from symmetrical to offset. Then, a systematic comparison of variable composite yarns with different frequencies (high, medium and low frequency) revealed that low-frequency step roll with wider grooves resulted in an intermittent output of staple fibers with less stress restraint, resulting in more pronounced structural variation in the siro and sirofil composite yarns with a slight yarn quality deterioration. Full article

(This article belongs to the Special Issue Advances in Fiber Materials and Manufacturing)

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19 pages, 4590 KiB

Open AccessArticle

Optimization of the Electrospray Process to Produce Lignin Nanoparticles for PLA-Based Food Packaging

by Rodrigue Daassi, Kalvin Durand, Denis Rodrigue and Tatjana Stevanovic

Polymers 2023, 15(13), 2973; https://doi.org/10.3390/polym15132973 - 7 Jul 2023

Cited by 15 | Viewed by 2575

Abstract

The development of new processing methods is required in order to meet the continuous demand for thinner films with excellent barrier properties for food packaging and other applications. In this study, rice husk organosolv lignin nanoparticles were prepared using the electrospray method, which [...] Read more.

The development of new processing methods is required in order to meet the continuous demand for thinner films with excellent barrier properties for food packaging and other applications. In this study, rice husk organosolv lignin nanoparticles were prepared using the electrospray method, which were applied to produce polylactic acid (PLA)-based films for food packaging. The effect of the following electrospray parameters has been investigated: lignin concentration (LC) ranging from 5–50 mg/mL, flow rate (FR) from 0.5–1 mL/min, applied voltage from 10–30 kV, and tip-to-collector distance (TCD) from 10–25 cm, on the morphology, size, polydispersity index (PDI), and Zeta potential (ZP) of lignin nanoparticles (LNPs). The response surface methodology with a Box-Behnken design was applied to optimize these parameters, while dynamic light scattering (DLS) and scanning electron microscopy (SEM) analyses were used to characterize the controlled LNPs. The results showed that the LNPs shape and sizes represent a balance between the solvent evaporation, LC, applied voltage, TCD and FR. The application of optimal electrospray conditions resulted in the production of LNPs with a spherical shape and a minimal size of 260 ± 10 nm, a PDI of 0.257 ± 0.02, and a ZP of −35.2 ± 4.1 mV. The optimal conditions were achieved at LC = 49.1 mg/mL and FR = 0.5 mL/h under an applied voltage of 25.4 kV and TCD = 22 cm. Then, the optimized LNPs were used to improve the properties of PLA-based films. Three types of PLA-lignin blend films were casted, namely lignin/PLA, LNPs/PLA and PLA-grafted LNPs. PLA-grafted LNPs exhibited a more uniform dispersion in PLA for lignin contents of up to 10% than other composite samples. Increasing the lignin content from 5% to 10% in PLA-grafted LNPs resulted in a significant increase in elongation at break (up to four times higher than neat PLA). The presence of PLA-grafted lignin led to a substantial reduction in optical transmittance in the UV range, dropping from 58.7 ± 3.0% to 1.10 ± 0.01%, while maintaining excellent transparency to visible light compared to blends containing lignin or LNPs. Although the antioxidant capacity of unmodified lignin is well-known, a substantial increase in antioxidant capacity was observed in LNPs and PLA-grafted LNP films, with values exceeding 10 times and 12 times that of neat PLA, respectively. These results confirm the significant potential of using studied films in food packaging applications. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Canada)

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Schematic diagram of lignin nanoparticle synthesis by electrospray and grafting of PLA. (a): electrospray with an aluminium plate as collector, (b): electrospray with a petri dish containing deionized water under electric field, (c): grafting of PLA via lactide ring-opening polymerization. Full article ">Figure 2
Effect of lignin concentration and flow rate on the morphology and size of lignin nanoparticles (LNPs). SEM micrograph of LNPS synthetized at: (A): 5 mg/mL, 0.5 mL/h, 20 kV, 20 cm; (B): 27.5 mg/mL, 0.75 mL/h, 30 kV, 20 cm; (C): 50 mg/mL, 1 mL/h, 30 kV, 10 cm; (D): 50 mg/mL, 0.5 mL/h, 20 kV; 10 cm. (E): LNPs particle size distribution obtained from SEM micrographs (A–D). Full article ">Figure 3
Response surface plot of LNPs size for the effect of lignin concentration and flow rate (A), lignin concentration and applied voltage (B), lignin concentration and tip-to-collector distance (C), flow rate and applied voltage (D), flow rate and tip-to-collector distance (E), and applied voltage and tip-to-collector distance (F). Full article ">Figure 4
Response surface plot of polydispersity index for the effect of lignin concentration and flow rate (A), lignin concentration and applied voltage (B), lignin concentration and tip-to-collector distance (C), flow rate and applied voltage (D), flow rate and tip-to-collector distance (E), and applied voltage and tip-to-collector distance (F). Full article ">Figure 5
Response surface plot of Zeta potential for the effect of lignin concentration and flow rate (A), lignin concentration and applied voltage (B), lignin concentration and tip-to-collector distance (C), flow rate and applied voltage (D), flow rate and tip-to-collector distance (E), and applied voltage and tip-to-collector distance (F). Full article ">Figure 6
SEM micrograph (A), TEM micrograph (B), and particle size distribution from SEM micrograph (C) of the optimized lignin nanoparticles from rice husk. Full article ">Figure 7
Fourier-transform infrared spectra of polylactic acid (PLA)-based composite films with 10% of lignin. Full article ">Figure 8
Transmittance (%) of neat PLA films and PLA blends containing lignin, lignin nanoparticles (LNPs), and PLA-grafted lignin nanoparticles (LNPs-PLA) with 1, 5, and 10% lignin content, measured at 280 nm (A) and 660 nm (B); (C) images of different films. For the bar plots, the error bars correspond to the average of transmittance results from triplicate. Bar plots with the same letter are not significantly different based on lignin content; LSD test p < 5%. Full article ">Figure 9
Thermal properties of neat PLA and PLA blend lignin composites, each sample containing 10% lignin: (A) TGA and DTG, and (B) DSC. Full article ">Figure 10
Mechanical properties of neat PLA sample, and film of PLA blend with lignin, lignin nanoparticles, and PLA-grafted LNPs each containing 1, 5, and 10% of lignin. Tensile strength (A), Young’s modulus (B), and elongation at break (C). Bar plot and error bars correspond to average of transmittance results and error type of triplicate. Bar plots with same letter are not significantly different with lignin content; LSD test p < 5%. Full article ">Figure 11
Antioxidant activity of neat PLA films and PLA composites such as PLA with lignin, lignin nanoparticles (LNPs), and PLA-grafted lignin nanoparticles (LNPs-PLA) with 0, 1, 5, and 10 wt.% lignin content, as determined by the DPPH assay. Bar plot and error bars correspond to the average and standard error of measurements in triplicate. Letters compare antioxidant activity of neat PLA films and PLA composites for each lignin content. LSD test p < 5%. Full article ">

45 pages, 6919 KiB

Open AccessReview

A Review on Reinforcements and Additives in Starch-Based Composites for Food Packaging

by Pedro Francisco Muñoz-Gimena, Víctor Oliver-Cuenca, Laura Peponi and Daniel López

Polymers 2023, 15(13), 2972; https://doi.org/10.3390/polym15132972 - 7 Jul 2023

Cited by 34 | Viewed by 8485

Abstract

The research of starch as a matrix material for manufacturing biodegradable films has been gaining popularity in recent years, indicating its potential and possible limitations. To compete with conventional petroleum-based plastics, an enhancement of their low resistance to water and limited mechanical properties [...] Read more.

The research of starch as a matrix material for manufacturing biodegradable films has been gaining popularity in recent years, indicating its potential and possible limitations. To compete with conventional petroleum-based plastics, an enhancement of their low resistance to water and limited mechanical properties is essential. This review aims to discuss the various types of nanofillers and additives that have been used in plasticized starch films including nanoclays (montmorillonite, halloysite, kaolinite, etc.), poly-saccharide nanofillers (cellulose, starch, chitin, and chitosan nanomaterials), metal oxides (titanium dioxide, zinc oxide, zirconium oxide, etc.), and essential oils (carvacrol, eugenol, cinnamic acid). These reinforcements are frequently used to enhance several physical characteristics including mechanical properties, thermal stability, moisture resistance, oxygen barrier capabilities, and biodegradation rate, providing antimicrobial and antioxidant properties. This paper will provide an overview of the development of starch-based nanocomposite films and coatings applied in food packaging systems through the application of reinforcements and additives. Full article

(This article belongs to the Special Issue Multifunctional Polymeric Formulations for Sustainable Food Packaging Applications)

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15 pages, 6190 KiB

Open AccessArticle

Thermal Performance of Multifunctional Facade Solution Containing Phase Change Materials: Experimental and Numerical Analysis

by C. Amaral, F. Gomez, M. Moreira, T. Silva and R. Vicente

Polymers 2023, 15(13), 2971; https://doi.org/10.3390/polym15132971 - 7 Jul 2023

Cited by 1 | Viewed by 1409

Abstract

This work focuses on the development and analysis of a new multifunctional facade panel incorporating PCM in foam layers. The thermal performance was analysed recurring to a hotbox heat flux meter method to determine the thermal transmittance (U-value) and the main findings are [...] Read more.

This work focuses on the development and analysis of a new multifunctional facade panel incorporating PCM in foam layers. The thermal performance was analysed recurring to a hotbox heat flux meter method to determine the thermal transmittance (U-value) and the main findings are presented. The experimental setup was based on the steady-state approach, using climatic chambers, assuring a stable thermal environment. Even small fractions of PCM achieved a small reduction in thermal amplitude. Numerical simulations using Ansys Fluent were developed to evaluate the performance of PCM use over a wide range of temperature boundary conditions and operating modes. These numerical models were calibrated and validated using the results of experimental tests, achieving a correlation factor of 0.9674, and, thus, accurately representing a real-world scenario. The decrement factor (f) was used to analyse the data. It was identified that the efficiency of the panel and size of the optimum region increased with the PCM fraction growth. The results showed the significant potential of the multi-layered panel, with the thermal regulator effect of the PCM incorporated, on indoor space temperature so as to reach good thermal comfort levels. The efficiency of the panel can be improved by nearly 50% depending on the input boundary conditions. The efficiency of the panel and the size of the optimum region increase with growth in the PCM fraction. The simulated behaviour was at an optimum when the input mean temperature was 20 °C for a room temperature of between 18–20 °C. Full article

(This article belongs to the Special Issue Polymers and Phase Change Materials: Past, Present and Future)

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25 pages, 7585 KiB

Open AccessReview

The Evolution and Future Trends of Unsaturated Polyester Biocomposites: A Bibliometric Analysis

by Piedad Gañán, Jaime Barajas, Robin Zuluaga, Cristina Castro, Daniel Marín, Agnieszka Tercjak and Daniel H. Builes

Polymers 2023, 15(13), 2970; https://doi.org/10.3390/polym15132970 - 6 Jul 2023

Cited by 8 | Viewed by 3159

Abstract

Unsaturated polyester resin (UPR) is one of the first commercialized polymer matrices for composites reinforced with glass fibers, but has remained popular to this day. To reduce their environmental impact, natural fibers have been used as reinforcements. Researchers all over the world are [...] Read more.

Unsaturated polyester resin (UPR) is one of the first commercialized polymer matrices for composites reinforced with glass fibers, but has remained popular to this day. To reduce their environmental impact, natural fibers have been used as reinforcements. Researchers all over the world are still interested in these composites, and numerous papers have been published in the last four decades. Using bibliometric analysis, this work provides compiled, structured, and relevant information about the evolution and current state of these materials. This first study on UPR biocomposites based on bibliometric analysis examined 531 published papers identified in the Scopus database from 1982 to July 2022. An analysis of the most active states, leading institutions, and leading authors is followed by the identification of key areas such as the most common natural fibers used as reinforcements, fiber treatments, and composite design parameters such as processing techniques; recently, composite testing; and technological applications. The findings emphasize the importance of staying active in this global field and provide information on novel promising topics for future research. Full article

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17 pages, 3721 KiB

Open AccessArticle

Electrospun Poly-L-Lactic Acid Scaffolds Surface-Modified via Reactive Magnetron Sputtering Using Different Mixing Ratios of Nitrogen and Xenon

by Pavel V. Maryin, Tuan-Hoang Tran, Anastasia A. Frolova, Mikhail A. Buldakov, Evgeny L. Choinzonov, Anna I. Kozelskaya, Sven Rutkowski and Sergei I. Tverdokhlebov

Polymers 2023, 15(13), 2969; https://doi.org/10.3390/polym15132969 - 6 Jul 2023

Cited by 4 | Viewed by 1612

Abstract

Controlled regeneration processes involving tissue growth using the surface and structure of scaffolds, are actively used in tissue engineering. Reactive magnetron sputtering is a versatile surface modification method of both metal and polymer substrates, as the properties of the formed coatings can be [...] Read more.

Controlled regeneration processes involving tissue growth using the surface and structure of scaffolds, are actively used in tissue engineering. Reactive magnetron sputtering is a versatile surface modification method of both metal and polymer substrates, as the properties of the formed coatings can be modified in a wide range by changing the process parameters. In magnetron sputtering, the working gas and its composition have an influence on the chemical composition and physical characteristics of the obtained coatings. However, there are no studies addressing the influence of the nitrogen/xenon gas mixture ratio in direct current magnetron sputtering on the deposition rate, physicochemical and in vitro properties of surface-modified biocompatible poly-L-lactic acid scaffolds. In this study, the application of mixtures of nitrogen and xenon in various ratios is demonstrated to modify the surface of non-woven poly-L-lactic acid scaffolds by direct current magnetron sputtering of a titanium target. It has been found that the magnetron sputtering parameters chosen do not negatively influence the morphology of the prepared scaffolds, but increase the hydrophilicity. Moreover, quantitative spectroscopic analysis results indicate that the formed coatings are primarily composed of titanium oxide and titanium oxynitride compounds and is dependent on the gas mixture ratio only to a certain extent. Atomic force microscopy investigations of the roughness of the fibers of the electrospun scaffolds and the thickness of the coatings formed on them show that the considerable variations observed in the intrinsic fiber reliefs are due to the formation of a fine layer on the fiber surfaces. The observed decrease in roughness after plasma modification is due to temperature and radiation effects of the plasma. In vitro experiments with human osteosarcoma cells show that the scaffolds investigated here have no cytotoxic effect on these cells. The cells adhere and proliferate well on each of the surface-modified electrospun scaffolds, with stimulation of cell differentiation in the osteogenic direction. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Recent Developments in Electrospinning)

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Experimental scheme of the fabrication of PLLA scaffolds, their surface modification via reactive DC magnetron sputtering of a titanium target using a gas mixture of nitrogen and xenon at different mixing ratios, and the investigation methods applied in this study. Full article ">Figure 2
Scanning electron microscope (SEM) micrographs on the left, histograms of the fiber diameters of the scaffold samples in the middle, and histograms of the pore areas of the scaffolds on the right: (a) Control samples (PLLA scaffolds without surface modification), (b) N2 100%, (c) N2 75% + Xe 25%, (d) N2 50% + Xe 50%, (e) N2 25% + Xe 75%, (f) Xe 100%. Full article ">Figure 3
(a) Glycerol contact angle (GCA) for the PLLA scaffold samples under investigation, and (b) coating thicknesses of all surface-modified samples. Full article ">Figure 4
High-resolution spectra obtained via XPS for all PLLA scaffold samples that are surface-modified with a mixture of nitrogen and xenon at mixing ratios: (a) Ti2p, (b) O1s, (c) N1s and (d) C1s. Full article ">Figure 5
Root mean square (RMS) roughness obtained by atomic force microscopy (AFM) at two different sized scanning areas of unmodified and surface-modified PLLA scaffold samples obtained at different mixing ratios of the working gases nitrogen and xenon at (a) 40 × 40 μm2 scanning area and (b) 3 × 3 μm2 scanning area. Full article ">Figure 6
(a) Amount for HOS cells present at the PLLA scaffold sample surfaces surface-modified using different mixing ratios of the working gases nitrogen and xenon. (b) Proliferative activity of HOS cells assessed via MTT assay (measured by absorbance and presents therefore the optical density). Full article ">Figure 7
Expression of (a) BGLAP and (b) SPP1 genes in HOS cells at day 14 after the start of incubation. Here, the P-Control samples indicate the level of proliferative activity of HOS cells placed into a polymeric Petri dish and then set to 100%. The statistical legend is as follows: *—statistically significant differences to the control samples are p < 0.05; #—the statistically significant differences to the samples N2 75% + Xe 25% are at p < 0.05; α—the statistically significant differences to the samples Xe 100% being p < 0.05. Full article ">

11 pages, 2902 KiB

Open AccessArticle

Development of Epoxy and Urethane Thermosetting Resin Using Chlorella sp. as Curing Agent for Materials with Low Environmental Impact

by Kohei Iritani, Akihito Nakanishi, Rinka Nihei, Shiomi Sugitani and Takashi Yamashita

Polymers 2023, 15(13), 2968; https://doi.org/10.3390/polym15132968 - 6 Jul 2023

Cited by 3 | Viewed by 1943

Abstract

In the current system, the disposal of plastic materials causes serious environmental pollution such as the generation of carbon dioxide and destruction of the ecosystem by micro-plastics. To solve this problem, bioplastics, biomass and biodegradable plastics have been developed. As part of our [...] Read more.

In the current system, the disposal of plastic materials causes serious environmental pollution such as the generation of carbon dioxide and destruction of the ecosystem by micro-plastics. To solve this problem, bioplastics, biomass and biodegradable plastics have been developed. As part of our research, we have developed novel bioplastics called “cell-plastics”, in which a unicellular green algal cell serves as a fundamental resource. The production of the cell-plastics would be expected to reduce environmental impact due to the usage of a natural product. Herein, to overcome the mechanical strength of cell-plastics, we used thermosetting epoxy and urethane resins containing Chlorella sp. as the green algae. We successfully fabricated thermosetting resins with a Chlorella sp. content of approximately 70 wt% or more. IR measurements revealed that the chemical structure of an epoxide or isocyanate monomer mixed with Chlorella sp. was modified, which suggests that the resins were hardened by the chemical reaction. In addition, we investigated the effect of thermosetting conditions such as temperature and compression for curing both resins. It was revealed that the Young’s moduli and tensile strengths were controlled by thermosetting temperature and compression, whereas the elongation ratios of the resins were constant at low values regardless of the conditions. Full article

(This article belongs to the Special Issue Biodegradable Polymers: Synthesis, Characterization and Applications)

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Chemical structures of BDE (a), BIC (b) and DBU (c), and chemical reactions of BDE (d) and BIC (e) with the hydroxyl group. Full article ">Figure 2
IR spectra of the thermosetting epoxy–cell (a,b) and urethane–cell (c,d) resins. Spectra enlarged for each wavelength region are shown in (b,d). The spectra of the mixture of monomer and Chlorella sp. After and before heat compression, Chlorella sp. and monomer are shown by red, blue, green and black lines. Full article ">Figure 3
SEM images of the surface and cross section of the thermosetting epoxy– (a) and urethane–cell (b) resins. Full article ">Figure 4
Typical stress–strain curves of the epoxy/cell (a) and urethane/cell (b) resins. The blue, red and green lines show the data of the resins formed at 120, 150 and 180 °C, respectively. The solid, dashed and dotted lines show the data of the resins formed at 20, 10 and 5 MPa, respectively. Full article ">Figure 5
TG (solid lines) and DTA (dashed lines) curves of the thermosetting epoxy– (red) and urethane–cell resins (blue) and Chlorella (green). Solid and dashed arrows indicate TG and DTA data, respectively. Full article ">

19 pages, 6905 KiB

Open AccessArticle

Surface Roughness and Grain Size Variation When 3D Printing Polyamide 11 Parts Using Selective Laser Sintering

by Riccardo Tonello, Knut Conradsen, David Bue Pedersen and Jeppe Revall Frisvad

Polymers 2023, 15(13), 2967; https://doi.org/10.3390/polym15132967 - 6 Jul 2023

Cited by 9 | Viewed by 2800

Abstract

Selective laser sintering (SLS) is a well-established technology that is used for additive manufacturing. Significant efforts have been made to improve SLS by optimizing the powder deposition, laser beam parameters, and temperature settings. The purpose is to ensure homogeneous sintering and prevent geometric [...] Read more.

Selective laser sintering (SLS) is a well-established technology that is used for additive manufacturing. Significant efforts have been made to improve SLS by optimizing the powder deposition, laser beam parameters, and temperature settings. The purpose is to ensure homogeneous sintering and prevent geometric and appearance inaccuracies in the manufactured objects. We evaluated the differences in the surface roughness and grain size of curved objects manufactured by using upcoming SLS technology that features two CO laser sources. Our analysis was carried out on polyamide 11 (PA11), which is a sustainable biobased polymer that has been gaining popularity due to its high-performance properties: its low melting point, high viscosity, and excellent mechanical properties. By using a Taguchi experimental design and analysis of variance (ANOVA), we examined the influence on the surface roughness and grain size of the build setup, the presence of thin walls, and the position of the sample on the powder bed. We found significant differences in some surface roughness and grain size measurements when these parameters were changed. Full article

(This article belongs to the Special Issue Progress in 3D Printing II)

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Chemical structure of PA. Full article ">Figure 2
Schematic representation of the coalescence process. A droplet of radius <math display="inline"><semantics><msub><mi>α</mi><mn>0</mn></msub></semantics></math> coalesces with another droplet and ends with the radius <math display="inline"><semantics><msub><mi>α</mi><mi>f</mi></msub></semantics></math>. During the process, the particle radius <math display="inline"><semantics><mi>α</mi></semantics></math> and the angle of the intersection <math display="inline"><semantics><mi>θ</mi></semantics></math> and the radius of the neck x change as a function of time t. Full article ">Figure 3
Schematic representation of the SLS technology. Full article ">Figure 4
3D model of the samples. Full sample (left), hollowed sample (right). Full article ">Figure 5
Layout of the print job for 94 samples on the same z-axis (top). The encircled samples were selected for analysis using confocal microscopy. Visualization in 3D of the 16 selected samples on the powder bed (bottom). Full article ">Figure 6
Numbers assigned to different positions in the powder bed for the pos factor in our factorial design. The red letter codes for the parts reveal their values for the build setup factor bus (U or not) and the design factor fuh (F or H). Full article ">Figure 7
Boxplots for some of the variables exhibiting significant differences in means with respect to different explanatory variables (pos, bus, fuh). Full article ">

19 pages, 5672 KiB

Open AccessArticle

Prospects for Recyclable Multilayer Packaging: A Case Study

by Martina Seier, Vasiliki-Maria Archodoulaki, Thomas Koch, Bernadette Duscher and Markus Gahleitner

Polymers 2023, 15(13), 2966; https://doi.org/10.3390/polym15132966 - 6 Jul 2023

Cited by 8 | Viewed by 5606

Abstract

Food preservation is an essential application for polymers, particularly in packaging. Complex multilayer films, such as those used for modified atmosphere packaging (MAP), extend the shelf life of sensitive foods. These mostly contain various polymers to achieve the necessary combination of mechanic, optic, [...] Read more.

Food preservation is an essential application for polymers, particularly in packaging. Complex multilayer films, such as those used for modified atmosphere packaging (MAP), extend the shelf life of sensitive foods. These mostly contain various polymers to achieve the necessary combination of mechanic, optic, and barrier properties that limit their recyclability. As the European Union’s Circular Economy Action Plan calls for sustainable products and business models, including waste prevention policies and recycling quotas, with plastic packaging being a high priority, solutions towards more sustainable multilayer packaging are urgently needed. This study evaluated and compared the recycling potential of functionally equivalent PET (polyethylene terephthalate) and PP (polypropylene) post-consumer MAP through structure analysis and recycling simulation. The structure analysis revealed that both types of MAP contained functional (stability) and barrier layers (oxygen and moisture). The recycling simulation showed that the PP-based packaging was recyclable 10 times, maintaining its mechanical properties and functionality. At the same time, the PET-based MAP resulted in a highly brittle material that was unsuitable for reprocessing into similar economic value products. The secondary material from the PP-based MAP was successfully manufactured into films, demonstrating the functional possibility of closed-loop recycling. The transition from a linear to a circular economy for MAP is currently still limited by safety concerns due to a lack of sufficient and efficient purification methods, but the proper design of multilayers for recyclability is a first step towards circularity. Full article

(This article belongs to the Special Issue Advanced Recycling of Plastic Waste: An Approach for Circular Economy)

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8 pages, 1377 KiB

Open AccessArticle

Bulk Polymerization of Acrylic Acid Using Dielectric-Barrier Discharge Plasma in a Mesoporous Material

by Matthew Mieles, Sky Harper and Hai-Feng Ji

Polymers 2023, 15(13), 2965; https://doi.org/10.3390/polym15132965 - 6 Jul 2023

Cited by 4 | Viewed by 3110

Abstract

This research investigated a non-thermal, dielectric-barrier discharge (DBD) plasma-based approach to prepare poly(acrylic acid) (PAA) from acrylic acid in its liquid state at atmospheric temperature and pressure. Neither additives nor solvents were needed, and the polymerization was accomplished both as a film and [...] Read more.

This research investigated a non-thermal, dielectric-barrier discharge (DBD) plasma-based approach to prepare poly(acrylic acid) (PAA) from acrylic acid in its liquid state at atmospheric temperature and pressure. Neither additives nor solvents were needed, and the polymerization was accomplished both as a film and inside a sheet of mesoporous paper. All prepared samples were characterized and the DBD plasma-initiated kinetics were analyzed for the polymerization of acrylic acid. Using FTIR semi-quantitative analysis, the degree of polymerization was monitored, and the reaction followed an overall second-order kinetic model with respect to the DBD-initiated polymerization. Additionally, the application of a PAA-modified paper as a water retention cloth or ‘wet wipe’ was investigated. The results showed that the PAA-modified paper substrates using DBD plasma increased water retention as a function of plasma treatment time. Full article

(This article belongs to the Special Issue Plasma Processing of Polymers)

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Scheme for the DBD plasma device. Full article ">Figure 2
FTIR spectra of acrylic acid (AA) and polyacrylic acid (PAA). Inset shows IR vibrational assignments for the carbonyl and vinylidene groups of AA. Full article ">Figure 3
(A) Plot of the FTIR peak area ratios (A1/A0) as a function of plasma treatment time. The A1 and A0 denote the peak areas of the 1636 cm−1 and 1700 cm−1 vibrational modes, respectively. (B) A second-order treatment of the A1/A0 ratio was plotted by graphing the inverse of this ratio as a function of treatment time. The inset shows several relevant parameters for the linear fit with an R-squared value of 0.98218. Full article ">Figure 4
FTIR spectra of acrylic acid monomer and paper substrate samples before and after 5 min of plasma exposure. Full article ">Figure 5
The mass loss due to water as a function of time. The black squares represent pristine paper, red circles represent the AA-modified paper before plasma treatment, and the blue triangles, magenta triangles, and green rhombuses represent the AA-modified paper after plasma treatments of 1, 2, and 5 min, respectively. Full article ">

12 pages, 4403 KiB

Open AccessArticle

Effect of Degradation in Small Intestinal Fluids on Mechanical Properties of Polycaprolactone and Poly-l-lactide-co-caprolactone

by Sam Peerlinck, Marc Miserez, Dominiek Reynaerts and Benjamin Gorissen

Polymers 2023, 15(13), 2964; https://doi.org/10.3390/polym15132964 - 6 Jul 2023

Viewed by 1770

Abstract

Polycaprolactone and poly-l-lactide-co-caprolactone are promising degradable biomaterials for many medical applications. Their mechanical properties, especially a low elastic modulus, make them particularly interesting for implantable devices and scaffolds that target soft tissues like the small intestine. However, the specific [...] Read more.

Polycaprolactone and poly-l-lactide-co-caprolactone are promising degradable biomaterials for many medical applications. Their mechanical properties, especially a low elastic modulus, make them particularly interesting for implantable devices and scaffolds that target soft tissues like the small intestine. However, the specific environment and mechanical loading in the intestinal lumen pose harsh boundary conditions on the design of these devices, and little is known about the degradation of those mechanical properties in small intestinal fluids. Here, we perform tensile tests on injection molded samples of both polymers during in vitro degradation of up to 70 days in human intestinal fluids. We report on yield stress, Young’s modulus, elongation at break and viscoelastic parameters describing both materials at regular time steps during the degradation. These characteristics are bench-marked against degradation studies of the same materials in other media. As a result, we offer time dependent mechanical properties that can be readily used for the development of medical devices that operate in the small intestine. Full article

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Full article ">Figure 1
Schematic of the material testing procedure; (A) tensile testing samples of PCL and PLCL are injection molded, (B) fresh small intestinal fluids are collected, (C) samples are submerged for their respective degradation time at 37 °C, while fluids are refreshed every 24 h, (D) tensile testing by imposing displacement on samples while recording reaction force and visual data, (E) post-processing of recorded data using Matlab, resulting in mechanical material properties over degradation time. Full article ">Figure 2
Observations made after degradation and during testing for PCL (top panes) and PLCL (bottom panes). The graphs show typical displacement- and force curves during tensile testing. (A,D) samples exhibited staining throughout degradation, without dimensional change. (B) Non-degraded PCL samples produce sharp high contrast images, and a well defined yield point as the samples show necking. (C) More degraded PCL samples (here 70 days) produced lower contrast images and display brittle fracture. (E) Non-degraded PLCL samples are partially transparent, producing low contrast images, without a clear yield point. (F) More degraded PLCL samples (here 56 days) display premature fracture, due to the appearance of multiple cracks in the reduced section. The locations of the considered yield points are indicated with a star. Full article ">Figure 3
Graphs displaying change in mechanical properties of PCL and PLCL. (A,B) change in yield stress and elongation at break relative to initial value, (C,D) absolute values of elasticity modulus, based on optical data (shaded area) and based on encoder data (solid lines). (E,F) change of each viscoelastic parameter (see Equation (<a href="#FD1-polymers-15-02964" class="html-disp-formula">1</a>)) relative to their initial, non-degraded, values. Full article ">Figure 4
Viscoelastic relaxation of a non-degraded PCL (A) and PLCL (B) sample, showing the dimensionless tensile modulus <math display="inline"><semantics><mrow><mi>E</mi><mo>/</mo><msub><mi>E</mi><mn>0</mn></msub></mrow></semantics></math>, where <math display="inline"><semantics><msub><mi>E</mi><mn>0</mn></msub></semantics></math> is the modulus at the onset of the stress relaxation. While the strain remains constant, the modulus decreases. This exponential decrease is fitted by the dimensionless relaxation modulus <math display="inline"><semantics><mrow><msub><mi>g</mi><mrow><mi>R</mi><mo>,</mo><mi>n</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow></mrow></semantics></math> (Equation (<a href="#FD1-polymers-15-02964" class="html-disp-formula">1</a>), using one term and two terms for comparison). Full article ">Figure 5
Comparison of the results with data from previous studies. (A) rate of change of yield stress and elasticity modulus of PCL in buffer solution (PBS) [<a href="#B20-polymers-15-02964" class="html-bibr">20</a>] versus small intestinal fluids and (B) comparison of data of the degradation of the elastic modulus from a literature review [<a href="#B3-polymers-15-02964" class="html-bibr">3</a>] and our results. Full article ">

20 pages, 2890 KiB

Open AccessArticle

The Influence of the Dispersion Method on the Morphological, Curing, and Mechanical Properties of NR/SBR Reinforced with Nano-Calcium Carbonate

by Mehrnoosh Damircheli and AmirHossein MajidiRad

Polymers 2023, 15(13), 2963; https://doi.org/10.3390/polym15132963 - 6 Jul 2023

Cited by 5 | Viewed by 2238

Abstract

There are several reasons for the development of nanopolymer compounds, such as improving physical, mechanical, and chemical properties, increasing lifespan, reducing costs, and decreasing negative environmental impact. The compatibility of two rubbers and mineral nanofillers in nanocomposites is a challenge that needs to [...] Read more.

There are several reasons for the development of nanopolymer compounds, such as improving physical, mechanical, and chemical properties, increasing lifespan, reducing costs, and decreasing negative environmental impact. The compatibility of two rubbers and mineral nanofillers in nanocomposites is a challenge that needs to be studied, and the effect of nanofillers on morphological, physical, and mechanical properties should be investigated accordingly. In this study, calcium carbonate nanoparticles were added to a polymer compound that included natural rubber (NR), styrene-butadiene rubber (SBR), vulcanization accelerators, and other additives. For mixing nanoparticles in the polymer matrix, various methods were used, including the solvent method in toluene and W410 solvents and the surface modification of calcium carbonate nanoparticles with stearic acid. The effect of dispersion nanoparticles in nanocomposite specimens on morphology, curing characteristics, and mechanical properties was studied. The morphologies of specimens were determined by X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM). The particle size of the nanocomposite was approximately 34 nm, and the interlayer spacing between crystal plates increased from 2.81 nm to 3.03 nm. These results indicate a uniform dispersion of nanoparticles, specifically with an optimum content of 3.52%, in the compounds prepared through all mixing methods, with no agglomeration observed in the nanocomposites. The results of the nanocomposites’ curing characterization demonstrate that with the addition of nanoparticles, a strong bond is created in the polymer chains, and curing properties are improved. Among the dispersion methods, the highest percentage improvement in curing properties is observed with the solvent method W410. To evaluate the effect of the addition of calcium carbonate nanoparticles and the dispersion method on improving mechanical properties, tensile, tear, hardness, and rebound resilience tests were performed. In tensile tests, the surface modification method showed the highest enhancement in ultimate stress (80%), followed by the W410 method (64%) and toluene method (63.7%). Tear strength improvements were highest in the W410-solvent sample (80%), followed by the surface modification method (57%) and the solvent-toluene method (50%). The W410 method resulted in the hardest samples, while the surface-modified samples had the lowest hardness. The addition of CaCO3 nanofillers reduced rebound resilience, with the W410 method experiencing the largest reduction (10.64%), followed by the toluene method (6.38%), and with the surface-modified samples showing the lowest reduction (4.25%). The results show that in the W410 solvent method, the nanocomposite is more elastic than for other methods. Additionally, for most of the mechanical properties, the W410 method results in the most growth in improvement. Full article

(This article belongs to the Topic Advanced Polymeric Composites: Processing, Characterization and Mechanical Behavior)

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13 pages, 2434 KiB

Open AccessReview

A Review of Developments in Polymer Stabilized Liquid Crystals

by Yong Ye, Li Guo and Tingjun Zhong

Polymers 2023, 15(13), 2962; https://doi.org/10.3390/polym15132962 - 6 Jul 2023

Cited by 22 | Viewed by 5074

Abstract

Polymer-stabilized liquid crystals (PSLCs) are multi-functional materials consisting of polymer networks in a continuous phase of liquid crystals (LCs), of which polymer networks provide anchoring energy to align the LCs. A number of improvements are detailed, including polymer-stabilized nematic liquid crystals (PSNLCs), polymer-stabilized [...] Read more.

Polymer-stabilized liquid crystals (PSLCs) are multi-functional materials consisting of polymer networks in a continuous phase of liquid crystals (LCs), of which polymer networks provide anchoring energy to align the LCs. A number of improvements are detailed, including polymer-stabilized nematic liquid crystals (PSNLCs), polymer-stabilized cholesteric liquid crystals (PSCLCs), polymer-stabilized blue phase liquid crystals (PSBPLCs), polymer-stabilized smectic liquid crystals (PSSLCs), polymer-stabilized ferroelectric liquid crystals (PSFLCs), and polymer-stabilized antiferroelectric liquid crystals (PSAFLCs) in this review. Polymer stabilization has achieved multiple functionalities for LCs; in smart windows, a sufficiently strong electric field allows the LCs to reorient and enables switching from a scattering (transparent) state to a transparent (scattering) state. For broadband reflectors, the reflection bandwidth of LCs is manually tuned by electric fields, light, magnetic fields, or temperature. PSBPLCs open a new way for next-generation displays, spatial light modulators, sensors, lasers, lenses, and photonics applications. Polymer networks in PSFLCs or PSAFLCs enhance their grayscale memories utilized in flexible displays and energy-saving smart cards. At the end, the remaining challenges and research opportunities of PSLCs are discussed. Full article

(This article belongs to the Special Issue Polymers Application in Electronics and Photonics)

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15 pages, 6082 KiB

Open AccessArticle

Antiviral Activity of Chitosan Nanoparticles and Chitosan Silver Nanocomposites against Alfalfa Mosaic Virus

by Sherif Mohamed El-Ganainy, Ahmed M. Soliman, Ahmed Mahmoud Ismail, Muhammad Naeem Sattar, Khaled Yehia Farroh and Radwa M. Shafie

Polymers 2023, 15(13), 2961; https://doi.org/10.3390/polym15132961 - 6 Jul 2023

Cited by 12 | Viewed by 3693

Abstract

Plant viruses are a global concern for sustainable crop production. Among the currently available antiviral approaches, nanotechnology has been overwhelmingly playing an effective role in circumventing plant viruses. Alfalfa mosaic virus (AMV) was isolated and identified from symptomatic pepper plants in Egypt using [...] Read more.

Plant viruses are a global concern for sustainable crop production. Among the currently available antiviral approaches, nanotechnology has been overwhelmingly playing an effective role in circumventing plant viruses. Alfalfa mosaic virus (AMV) was isolated and identified from symptomatic pepper plants in Egypt using symptomatology, serological tests using the direct ELISA technique, differential hosts and electron microscopy. The virus was biologically purified from a single local lesion that developed on Chenopodium amaranticolor. The AMV infection was further confirmed using an AMV coat protein-specific primer RT-PCR. We further evaluated the antiviral potential of chitosan nanoparticles (CS-NPs) and chitosan silver nanocomposites (CS-Ag NC) in different concentrations against AMV infections in pepper plants. All tested concentrations of CS-NPs and CS-Ag NC induced the inhibition of AMV systemically infected pepper plants when applied 24 h after virus inoculation. The foliar application of 400 ppm CS-NPs or 200 ppm CS-Ag NC produced the highest AMV inhibitory effect (90 and 91%) when applied 24 h after virus inoculation. Treatment with CS-NPs and CS-Ag NC considerably increased the phenol, proline and capsaicin contents compared to the infected plants. Moreover, the agronomic metrics (plant height, fresh and dry pod weights and number of pods per plant) were also significantly improved. According to our results, the potential applications of CS-NPs and CS-Ag NC may provide an effective therapeutic measure for better AMV and other related plant virus management. Full article

(This article belongs to the Collection Sustainable Polymer/Biopolymer-Based Composites: Processing, Characterization, and Application)

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11 pages, 1291 KiB

Open AccessArticle

Comparative Study on the Stiffness of Poly(lactic acid) Reinforced with Untreated and Bleached Hemp Fibers

by Roberto J. Aguado, Gabriela A. Bastida, Francisco X. Espinach, Joan Llorens, Quim Tarrés, Marc Delgado-Aguilar and Pere Mutjé

Polymers 2023, 15(13), 2960; https://doi.org/10.3390/polym15132960 - 6 Jul 2023

Cited by 3 | Viewed by 1771

Abstract

Composite materials containing natural reinforcement fibers, generally called biocomposites, have attracted the interest of both researchers and manufacturers, but the most environmentally advantageous combinations include a bio-based matrix, as well. With this in mind, a poly(lactic acid) (PLA) matrix was reinforced with natural [...] Read more.

Composite materials containing natural reinforcement fibers, generally called biocomposites, have attracted the interest of both researchers and manufacturers, but the most environmentally advantageous combinations include a bio-based matrix, as well. With this in mind, a poly(lactic acid) (PLA) matrix was reinforced with natural fibers from hemp, both untreated strands (UHSs) and soda-bleached fibers (SBHFs). The preparation of the subsequent fully bio-sourced, discontinuously reinforced composites involved kinetic mixing, intensive single-screw extrusion, milling, and injection molding. Up to a fiber content of 30 wt%, the tensile modulus increased linearly with the volume fraction of the dispersed phase. Differences between SBHFs (up to 7.6 Gpa) and UHSs (up to 6.9 Gpa) were hardly significant (p = 0.1), but SBHF-reinforced composites displayed higher strain at failure. In any case, for the same fiber load (30 wt%), the Young’s modulus of PLA/hemp biocomposites was greater than that of glass fiber (GF)-reinforced polypropylene (5.7 GPa), albeit lower than that of PLA/GF (9.8 GPa). Considering all the measurements, the contribution of each phase was analyzed by applying the Hirsch model and the Tsai-Pagano model. As a concluding remark, although the intrinsic tensile modulus of SBHFs was lower than that of GF, the efficiency of those natural fibers as reinforcement (according to the rule of mixtures) was found to be higher. Full article

(This article belongs to the Special Issue Advances in Cellulose-Based Polymers and Composites)

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21 pages, 11824 KiB

Open AccessArticle

Degradation Behavior of Biodegradable Man-Made Fibers in Natural Soil and in Compost

by Pia Borelbach, Rodion Kopitzky, Jörg Dahringer and Patrick Gutmann

Polymers 2023, 15(13), 2959; https://doi.org/10.3390/polym15132959 - 6 Jul 2023

Cited by 16 | Viewed by 3547

Abstract

In open environment applications, fibers are increasingly being used that are expected to biodegrade in the soil after their desired service life. Biodegradable polymer fibers are a versatile alternative to natural fibers. In this study, the degradation behavior of fibers made from polylactic [...] Read more.

In open environment applications, fibers are increasingly being used that are expected to biodegrade in the soil after their desired service life. Biodegradable polymer fibers are a versatile alternative to natural fibers. In this study, the degradation behavior of fibers made from polylactic acid (PLA) and a polyhydroxy alkanoate (PHA) blend with PLA, as well as a bicomponent fiber (BICO) made from polybutylene succinate (PBS) and PLA, was investigated. The fibers were stored in topsoil at 23 °C for 12 weeks. In addition, fibers were stored in compost at 58 °C for 4 weeks to investigate the degradation behavior in an industrial composting plant. Reference materials were also stored without substrate under the same temperatures and humidity conditions. Samples were taken regularly, and mechanical testing, scanning electron microscopy (SEM), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and infrared spectroscopy (IR) were used to study the degradation of the fibers. After 12 weeks in soil at ambient temperatures, the PLA and BICO fibers showed no degradation. The PHA fibers showed cracks in SEM, a decrease in molecular weight, and changes in the IR spectrum. No evidence of biological influence (bacteria or fungi) was found. Under industrial composting conditions, all fibers showed a decrease in strength and molecular weight. For the BICO and the PHA fibers, the SEM images show significant changes. Especially in the PHA fibers, fungal mycelia can be seen. The studies provide a better insight into the processes involved in the degradation behavior under different environmental conditions. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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21 pages, 20381 KiB

Open AccessArticle

Fracture of Epoxy Matrixes Modified with Thermo-Plastic Polymers and Winding Glass Fibers Reinforced Plastics on Their Base under Low-Velocity Impact Condition

by Ilya V. Tretyakov, Tuyara V. Petrova, Aleksey V. Kireynov, Roman A. Korokhin, Elena O. Platonova, Olga V. Alexeeva, Yulia A. Gorbatkina, Vitaliy I. Solodilov, Gleb Yu. Yurkov and Alexander Al. Berlin

Polymers 2023, 15(13), 2958; https://doi.org/10.3390/polym15132958 - 5 Jul 2023

Cited by 4 | Viewed by 1463

Abstract

The work is aimed at studying the impact resistance of epoxy oligomer matrices (EO) modified with polysulfone (PSU) or polyethersulfone (PES) and glass fibers reinforced plastics (GFRP) based on them under low-velocity impact conditions. The concentration dependences of strength and fracture energy of [...] Read more.

The work is aimed at studying the impact resistance of epoxy oligomer matrices (EO) modified with polysulfone (PSU) or polyethersulfone (PES) and glass fibers reinforced plastics (GFRP) based on them under low-velocity impact conditions. The concentration dependences of strength and fracture energy of modified matrices and GFRP were determined. It has been determined that the type of concentration curves of the fracture energy of GFRP depends on the concentration and type of the modifying polymer. It is shown that strength σ and fracture energy E_M of thermoplastic-modified epoxy matrices change little in the concentration range from 0 to 15 wt.%. However, even with the introduction of 20 wt.% PSU into EO, the strength increases from 164 MPa to 200 MPa, and the fracture energy from 32 kJ/m² to 39 kJ/m². The effect of increasing the strength and fracture energy of modified matrices is retained in GFRP. The maximum increase in shear strength (from 72 MPa to 87 MPa) is observed for GFRP based on the EO + 15 wt.% PSU matrix. For GFRP based on EO + 20 wt.% PES, the shear strength is reduced to 69 MPa. The opposite effect is observed for the EO + 20 wt.% PES matrix, where the strength value decreases from 164 MPa to 75 MPa, and the energy decreases from 32 kJ/m² to 10 kJ/m². The reference value for the fracture energy of GFRP 615 is 741 kJ/m². The maximum fracture energy for GFRP is based on EO + 20 wt.% PSU increases to 832 kJ/m² for GFRP based on EO + 20 wt.% PES—up to 950 kJ/m². The study of the morphology of the fracture surfaces of matrices and GFRP confirmed the dependence of impact characteristics on the microstructure of the modified matrices and the degree of involvement in the process of crack formation. The greatest effect is achieved for matrices with a phase structure “thermoplastic matrix-epoxy dispersion.” Correlations between the fracture energy and strength of EO + PES matrices and GFRP have been established. Full article

(This article belongs to the Collection Reinforced Polymer Composites)

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11 pages, 7664 KiB

Open AccessArticle

Effect of Grafting Conditions on the Interfacial Properties of Silane Modified Wood Veneer/PE Film Plywood

by Liang Chang, Yuanwu Wang, Xueqi Chen, Yiping Ren and Xiaoxi Luo

Polymers 2023, 15(13), 2957; https://doi.org/10.3390/polym15132957 - 5 Jul 2023

Viewed by 1442

Abstract

In order to elucidate the importance of grafting in the compatibilization process of silane coupling agents, poplar veneer was treated with silane coupling agents and grafted under different heating conditions. The treated veneers were used composited with PE film to prepare different plywood [...] Read more.

In order to elucidate the importance of grafting in the compatibilization process of silane coupling agents, poplar veneer was treated with silane coupling agents and grafted under different heating conditions. The treated veneers were used composited with PE film to prepare different plywood samples. XPS and WCA were used to analyze the effect of grafting conditions on the surface properties of the silane-treated veneer. The results showed that free silanols can physically be adsorbed onto all silane-treated veneer surfaces, forming hydrogen–Si–O–Si– bonds and therefore increasing the water contact angle. Only under heating conditions could the –Si–O–Si– be converted into covalent –Si–O–C– bonds, which helped to improve the bonding strength. When silane-treated veneer was grafted at 120 °C for 90 min, the tensile shear strength of plywood reached 1.03 MPa, meeting the requirements of GB/T 9846.3-2004 for outdoor materials. Enhanced interlock between silane-modified veneer and PE film was observed under the optimal grafting condition by SEM. The better interface structure allowed improvement of thermal stability. DMA results showed that the retention rate in storage modulus at 130 °C was 60% for the grafted sample, while the retention rate for the ungrafted sample was only 31%. Full article

(This article belongs to the Special Issue Wood Polymer Composites in Engineering and Environmental Applications)

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16 pages, 7009 KiB

Open AccessArticle

An Atomistic Study of the Tensile Deformation of Carbon Nanotube–Polymethylmethacrylate Composites

by Anshu Raj, Sk Md Ahnaf Akif Alvi, Khayrul Islam, Mohammad Motalab and Shuozhi Xu

Polymers 2023, 15(13), 2956; https://doi.org/10.3390/polym15132956 - 5 Jul 2023

Cited by 4 | Viewed by 2611

Abstract

There has been growing interest in polymer/carbon nanotube (CNT) composites due to an exceptional enhancement in mechanical, structural, thermal, and electronic properties resulting from a small percentage of CNTs. However, the performance of these composites is influenced by the type of polymer used. [...] Read more.

There has been growing interest in polymer/carbon nanotube (CNT) composites due to an exceptional enhancement in mechanical, structural, thermal, and electronic properties resulting from a small percentage of CNTs. However, the performance of these composites is influenced by the type of polymer used. PMMA is a polymer of particular interest among many other polymers because of its biomaterial applications due to its biocompatibility, non-toxicity, and non-biodegradability. In this research, we utilized a reactive force field to conduct molecular dynamics simulations to investigate changes in the mechanical properties of single-walled carbon nanotube (SWCNT)-reinforced Poly (methyl methacrylate) (PMMA) matrix composites. To explore the potential of SWCNT-reinforced PMMA composites in these applications, we conducted simulations with varying CNT diameters (0.542–1.08 nm), CNT volume fractions (8.1–16.5%), and temperatures (100 K–700 K). We also analyzed the dependence of Young’s modulus and interaction energy with different CNT diameters, along with changes in fracture toughness with varying temperatures. Our findings suggest that incorporating a small amount of SWCNT into the PMMA polymer matrix could significantly enhance the mechanical properties of the resulting composite. It is also found that the double-walled carbon nanotube has roughly twice the tensile strength of SWCNT, while maintaining the same simulation cell dimensions. Full article

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20 pages, 6874 KiB

Open AccessArticle

Laminar Biomaterial Composite of PVA Cryogel with Amnion as Potential Wound Dressing

by Łukasz Otulakowski, Agnieszka Klama-Baryła, Anna Celny, Maciej Kasprów, Anna Hercog, Marcin Godzierz, Anna Sitkowska, Sławomir Kadłubowski, Magdalena Jaworska, Ewa Chmielik, Barbara Trzebicka and Alicja Utrata-Wesołek

Polymers 2023, 15(13), 2955; https://doi.org/10.3390/polym15132955 - 5 Jul 2023

Cited by 1 | Viewed by 1940

Abstract

Gel dressings, composed of polymers both natural and synthetic, are successfully used in the treatment of burn wounds. They protect the burn wound site against adverse external factors, ensure an adequate level of tissue hydration, have soothing and pain-relieving properties, and also support [...] Read more.

Gel dressings, composed of polymers both natural and synthetic, are successfully used in the treatment of burn wounds. They protect the burn wound site against adverse external factors, ensure an adequate level of tissue hydration, have soothing and pain-relieving properties, and also support the healing process and reduce the risk of pathological scars. Another promising material that can be used in the wound-healing process is an amnion membrane. Due to its valuable properties such as protecting the body against bacterial infections and permeability to nutrition, it has found usage in different brands of medicine. In this work, we have combined the beneficial properties of hydrogels and amnion in order to make the laminar dressing that may serve for wound healing. For that purpose, the physically crosslinked cryogel of poly(vinyl alcohol) (PVA) was covered with an amnion membrane. Subsequently, gamma irradiation was performed, leading to the simultaneous internal crosslinking of the hydrogel, its permanent bonding with the amnion, and dressing sterilization. The physicochemical properties of the dressing including gel fraction, swelling, and hardness were studied. Biological tests such as the MTT assay, antimicrobial activity, and histopathological examination confirmed that the obtained material constituted a promising candidate for further, more in-depth studies aiming at wound dressing application. Full article

(This article belongs to the Special Issue Advances in Polymeric Biomaterials: Drug Delivery and Tissue Engineering II)

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14 pages, 3517 KiB

Open AccessArticle

Probing the Effect of Photovoltaic Material on V_oc in Ternary Polymer Solar Cells with Non-Fullerene Acceptors by Machine Learning

by Di Huang, Zhennan Li, Kuo Wang, Haixin Zhou, Xiaojie Zhao, Xinyu Peng, Rui Zhang, Jipeng Wu, Jiaojiao Liang and Ling Zhao

Polymers 2023, 15(13), 2954; https://doi.org/10.3390/polym15132954 - 5 Jul 2023

Cited by 7 | Viewed by 1744

Abstract

The power conversion efficiency (PCE) of ternary polymer solar cells (PSCs) with non-fullerene has a phenomenal increase in recent years. However, improving the open circuit voltage (V_oc) of ternary PSCs with non-fullerene still remains a challenge. Therefore, in this work, machine [...] Read more.

The power conversion efficiency (PCE) of ternary polymer solar cells (PSCs) with non-fullerene has a phenomenal increase in recent years. However, improving the open circuit voltage (V_oc) of ternary PSCs with non-fullerene still remains a challenge. Therefore, in this work, machine learning (ML) algorithms are employed, including eXtreme gradient boosting, K-nearest neighbor and random forest, to quantitatively analyze the impact mechanism of V_oc in ternary PSCs with the double acceptors from the two aspects of photovoltaic materials. In one aspect of photovoltaic materials, the doping concentration has the greatest impact on V_oc in ternary PSCs. Furthermore, the addition of the third component affects the energy offset between the donor and acceptor for increasing V_oc in ternary PSCs. More importantly, to obtain the maximum V_oc in ternary PSCs with the double acceptors, the HOMO and LUMO energy levels of the third component should be around (−5.7 ± 0.1) eV and (−3.6 ± 0.1) eV, respectively. In the other aspect of molecular descriptors and molecular fingerprints in the third component of ternary PSCs with the double acceptors, the hydrogen bond strength and aromatic ring structure of the third component have high impact on the V_oc of ternary PSCs. In partial dependence plot, it is clear that when the number of methyl groups is four and the number of carbonyl groups is two in the third component of acceptor, the V_oc of ternary PSCs with the double acceptors can be maximized. All of these findings provide valuable insights into the development of materials with high V_oc in ternary PSCs for saving time and cost. Full article

(This article belongs to the Special Issue Polymers for Electronics and Energy Devices)

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28 pages, 1435 KiB

Open AccessReview

Chitosan-Based Nano Systems for Natural Antioxidants in Breast Cancer Therapy

by Yedi Herdiana, Patihul Husni, Siti Nurhasanah, Shaharum Shamsuddin and Nasrul Wathoni

Polymers 2023, 15(13), 2953; https://doi.org/10.3390/polym15132953 - 5 Jul 2023

Cited by 22 | Viewed by 3320

Abstract

Breast cancer is a major cause of death globally, accounting for around 13% of all deaths. Chemotherapy, the common treatment for cancer, can have side effects that lead to the production of reactive oxygen species (ROS) and an increase in oxidative stress in [...] Read more.

Breast cancer is a major cause of death globally, accounting for around 13% of all deaths. Chemotherapy, the common treatment for cancer, can have side effects that lead to the production of reactive oxygen species (ROS) and an increase in oxidative stress in the body. Antioxidants are important for maintaining the health of cells and helping the immune system function properly. They play a crucial role in balancing the body’s internal environment. Using natural antioxidants is an alternative to mitigate the harmful effects of oxidative stress. However, around 80% of natural antioxidants have limited effectiveness when taken orally because they do not dissolve well in water or other solvents. This poor solubility affects their ability to be absorbed by the body and limits their bioavailability. One strategy that has been considered is to increase their water solubility to increase their oral bioavailability. Chitosan-based nanoparticle (CSNP) systems have been extensively explored due to their reliability and simpler synthesis routes. This review focuses on the various methods of chitosan-based nanoformulation for developing effective oral dosage forms for natural antioxidants based on the pharmacokinetics and pharmacodynamics properties. Chitosan (CS) could be a model, because of its wide use in polymeric NPs research, thus providing a better understanding of the role of vehicles that carry natural antioxidants in maintaining the stability and enhancing the performance of cancer drugs. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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14 pages, 2252 KiB

Open AccessArticle

Early In Vivo Osteogenic and Inflammatory Response of 3D Printed Polycaprolactone/Carbon Nanotube/Hydroxyapatite/Tricalcium Phosphate Composite Scaffolds

by Paulo Roberto Lopes Nalesso, Matheus Vedovatto, Julia Eduarda Schneider Gregório, Boyang Huang, Cian Vyas, Milton Santamaria-Jr, Paulo Bártolo and Guilherme Ferreira Caetano

Polymers 2023, 15(13), 2952; https://doi.org/10.3390/polym15132952 - 5 Jul 2023

Cited by 5 | Viewed by 2121

Abstract

The development of advanced biomaterials and manufacturing processes to fabricate biologically and mechanically appropriate scaffolds for bone tissue is a significant challenge. Polycaprolactone (PCL) is a biocompatible and degradable polymer used in bone tissue engineering, but it lacks biofunctionalization. Bioceramics, such as hydroxyapatite [...] Read more.

The development of advanced biomaterials and manufacturing processes to fabricate biologically and mechanically appropriate scaffolds for bone tissue is a significant challenge. Polycaprolactone (PCL) is a biocompatible and degradable polymer used in bone tissue engineering, but it lacks biofunctionalization. Bioceramics, such as hydroxyapatite (HA) and β tricalcium phosphate (β-TCP), which are similar chemically to native bone, can facilitate both osteointegration and osteoinduction whilst improving the biomechanics of a scaffold. Carbon nanotubes (CNTs) display exceptional electrical conductivity and mechanical properties. A major limitation is the understanding of how PCL-based scaffolds containing HA, TCP, and CNTs behave in vivo in a bone regeneration model. The objective of this study was to evaluate the use of three-dimensional (3D) printed PCL-based composite scaffolds containing CNTs, HA, and β-TCP during the initial osteogenic and inflammatory response phase in a critical bone defect rat model. Gene expression related to early osteogenesis, the inflammatory phase, and tissue formation was evaluated using quantitative real-time PCR (RT-qPCR). Tissue formation and mineralization were assessed by histomorphometry. The CNT+HA/TCP group presented higher expression of osteogenic genes after seven days. The CNT+HA and CNT+TCP groups stimulated higher gene expression for tissue formation and mineralization, and pro- and anti-inflammatory genes after 14 and 30 days. Moreover, the CNT+TCP and CNT+HA/TCP groups showed higher gene expressions related to M1 macrophages. The association of CNTs with ceramics at 10wt% (CNT+HA/TCP) showed lower expressions of inflammatory genes and higher osteogenic, presenting a positive impact and balanced cell signaling for early bone formation. The association of CNTs with both ceramics promoted a minor inflammatory response and faster bone tissue formation. Full article

(This article belongs to the Special Issue Polymers and Biocomposites Application in Bone Tissue Engineering)

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Osteogenic gene expression (qPCR) showing the fold change for (A) Runx-2, (B) Osterix, (C) Bmp-2, (D) Bmp-7, and (E) Vegf at days 7, 14, 30 and 60 in PCL, CNT+HA, CNT+TCP, and CNT +HA/TCP. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.005. Full article ">Figure 2
Inflammatory gene expression (qPCR) showing the fold change for (A) Il-1β, (B) Il-6, (C) Ccr7, (D) CD86, and (E) CD68 at days 7, 14, 30, and 60 in PCL, CNT+HA, CNT+TCP, and CNT+HA/TCP. * p < 0.05, ** p < 0.01. Full article ">Figure 3
Anti-inflammatory gene expression (qPCR) showing the fold change for (A) Il-10, (B) CD163, (C) Il-1rn, and (D) Arg1 at days 7, 14, 30, and 60 in PCL, CNT+HA, CNT+TCP, and CNT+HA/TCP. * p < 0.05, ** p < 0.01, *** p < 0.001. Full article ">Figure 4
Gene expression (qPCR) showing the fold change for (A) Osteopontin, (B) Collagen I; and histomorphometry for (C) connective tissue percentage, and (D) mineralized tissue percentage at days 30 and 60 in PCL, CNT+HA, CNT+TCP, and CNT+HA/TCP. Full article ">Figure 5
Photomicrography stained with Masson Trichrome (200× magnification) showing the tissue formation in the scaffolds after 30 days (A–C) and 60 days (D–F). MT: mineralized tissue; CT: connective tissue; BV: blood vessel; S: scaffolds fibres (scale = 200 µm). Full article ">

28 pages, 6816 KiB

Open AccessReview

The Difference in Performance and Compatibility between Crystalline and Amorphous Fillers in Mixed Matrix Membranes for Gas Separation (MMMs)

by Mariolino Carta, Ariana R. Antonangelo, Johannes Carolus Jansen and Mariagiulia Longo

Polymers 2023, 15(13), 2951; https://doi.org/10.3390/polym15132951 - 5 Jul 2023

Cited by 7 | Viewed by 2509

Abstract

An increasing number of high-performing gas separation membranes is reported almost on a daily basis, yet only a few of them have reached commercialisation while the rest are still considered pure research outcomes. This is often attributable to a rapid change in the [...] Read more.

An increasing number of high-performing gas separation membranes is reported almost on a daily basis, yet only a few of them have reached commercialisation while the rest are still considered pure research outcomes. This is often attributable to a rapid change in the performance of these separation systems over a relatively short time. A common approach to address this issue is the development of mixed matrix membranes (MMMs). These hybrid systems typically utilise either crystalline or amorphous additives, so-called fillers, which are incorporated into polymeric membranes at different loadings, with the aim to improve and stabilise the final gas separation performance. After a general introduction to the most relevant models to describe the transport properties in MMMs, this review intends to investigate and discuss the main advantages and disadvantages derived from the inclusion of fillers of different morphologies. Particular emphasis will be given to the study of the compatibility at the interface between the filler and the matrix created by the two different classes of additives, the inorganic and crystalline fillers vs. their organic and amorphous counterparts. It will conclude with a brief summary of the main findings. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films II)

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14 pages, 4887 KiB

Open AccessArticle

Experimental Investigation of Polymer Injection in High Permeability Conduits for Material Sustainability and Behavior in Oil Reservoirs

by Sherif Fakher and Abdelaziz Lafi Khlaifat

Polymers 2023, 15(13), 2950; https://doi.org/10.3390/polym15132950 - 5 Jul 2023

Cited by 6 | Viewed by 2093

Abstract

Polymers are one of the most widely used chemicals in the oil and gas industry. They are used for mobility control in enhanced oil recovery, in conformance control as a cross-linked plugging agent, as a fracking fluid for fracture propagation and proppant transportation, [...] Read more.

Polymers are one of the most widely used chemicals in the oil and gas industry. They are used for mobility control in enhanced oil recovery, in conformance control as a cross-linked plugging agent, as a fracking fluid for fracture propagation and proppant transportation, and in drilling fluids as an additive for drilling mud enhancement. This research characterizes the polymer injectivity in different pore sizes under different conditions and evaluates the polymer conditions after injection. Based on this, the ability to reinject the polymer in the porous media is discussed. The factors studied include the pore size, the polymer concentration, the polymer injection flowrate, and polymer injectivity. When the porous media size was reduced to 1.59 mm (1/16th of an inch), the injectivity value reduced significantly, reaching less than 0.2 mL/min/psi and the polymer degradation increased primarily due to shearing. Results also showed that the polymers underwent four main degradations during injection including dehydration, syneresis, shearing, and excessive hydrolysis. In continuous fractures, the degradation is a strong function of the fracture size, length, and the polymer structure. The experimental results showed that one or more of the polymer degradations resulted in the inability to reinject the polymer in most cases. Full article

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15 pages, 4670 KiB

Open AccessArticle

Synergistic Effect of Zinc-Chitosan Nanoparticles and Hydroxychloroquine to Inhibit Buffalo Coronavirus

by Anju Manuja, Balvinder Kumar, Dharvi Chhabra, Basanti Brar, Riyesh Thachamvally, Yash Pal and Minakshi Prasad

Polymers 2023, 15(13), 2949; https://doi.org/10.3390/polym15132949 - 5 Jul 2023

Cited by 9 | Viewed by 2139

Abstract

Zinc ions can hinder the synthesis of proteins required for accomplishing several stages of the viral life cycle. The intracellular zinc concentration can be increased by using zinc ionophores which transport zinc ions into the cells and hinder viral replication. (Hydroxy)chloroquine is an [...] Read more.

Zinc ions can hinder the synthesis of proteins required for accomplishing several stages of the viral life cycle. The intracellular zinc concentration can be increased by using zinc ionophores which transport zinc ions into the cells and hinder viral replication. (Hydroxy)chloroquine is an example of a zinc ionophore, but both zinc and (hydroxy)chloroquine can be toxic to the host organism. The nanocarriers may serve as camouflage to evade the adverse effects of drugs, chemicals, and nanoparticles on the host. We formulated ZnO nanoparticles with flower-like morphology (ZnONFs). It was further decorated with chitosan along with hydroxychloroquine (as a zinc ionophore) (CHCZnO NPs). We have chosen the cationic polymer chitosan since it is biocompatible, biodegradable and binds easily with the cells, and enhances the transport of drugs across cell membranes. The formulation was investigated for size, shape, surface charge, and interaction of chemicals used. We evaluated the formulations for cytotoxicity, and biocompatibility in embryonated chicks and their efficacy against bovine coronavirus (BCoV) isolated from a buffalo calf, and pneumo-enteric coronaviruses isolated from a buffalo calf with promising results in comparison to ZnONFs/hydroxychloroquine alone. Furthermore, we elucidate the mechanism underlying the lysosomotropic effect of various formulations on Vero cells infected with the buffalo coronavirus. Full article

(This article belongs to the Special Issue Eco-Friendly Polymers: Synthesis, Characterization and Applications II)

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15 pages, 3520 KiB

Open AccessArticle

Efficient Removal of Carcinogenic Azo Dyes from Water Using Iron(II) Clathrochelate Derived Metalorganic Copolymers Made from a Copper-Catalyzed [4 + 2] Cyclobenzannulation Reaction

by Noorullah Baig, Suchetha Shetty, Rupa Bargakshatriya, Sumit Kumar Pramanik and Bassam Alameddine

Polymers 2023, 15(13), 2948; https://doi.org/10.3390/polym15132948 - 4 Jul 2023

Cited by 7 | Viewed by 1817

Abstract

A novel synthetic strategy is disclosed to prepare a new class of metalorganic copolymers that contain iron(II) clathrochelate building blocks by employing a mild and cost-effective copper-catalyzed [4 + 2] cyclobenzannulation reaction, using three specially designed diethynyl iron(II) clathrochelate synthons. The target copolymers [...] Read more.

A novel synthetic strategy is disclosed to prepare a new class of metalorganic copolymers that contain iron(II) clathrochelate building blocks by employing a mild and cost-effective copper-catalyzed [4 + 2] cyclobenzannulation reaction, using three specially designed diethynyl iron(II) clathrochelate synthons. The target copolymers CBP1-3 were isolated in high purity and excellent yields as proven by their structural and photophysical characterization, namely, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and UV–VIS absorption and emission spectroscopies. The thermogravimetric analysis (TGA) of CBP1-3 revealed an excellent chemical stability. Investigation of the adsorption properties of the target copolymers towards the carcinogenic methyl red dye from aqueous solution revealed a quantitative uptake in 30 min. Isothermal adsorption studies disclosed that methyl red uptake from aqueous solution followed the Langmuir model for all of the target copolymers, reaching a maximum adsorption capacity (q_m) of 431 mg g⁻. Kinetic investigation revealed that the adsorption followed pseudo-first-order with an equilibrium adsorption capacity (q_e,cal) of 79.35 mg g⁻ and whose sorption property was sustained even after its reuse several times. Full article

(This article belongs to the Special Issue Advances in Functional Hybrid Polymeric Composites)

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17 pages, 5738 KiB

Open AccessArticle

Effect of Synthetic Low-Odor Thiol-Based Hardeners Containing Hydroxyl and Methyl Groups on the Curing Behavior, Thermal, and Mechanical Properties of Epoxy Resins

by Young-Hun Kim, Jeong Ju Baek, Ki Cheol Chang, Baek Soo Park, Won-Gun Koh and Gyojic Shin

Polymers 2023, 15(13), 2947; https://doi.org/10.3390/polym15132947 - 4 Jul 2023

Cited by 3 | Viewed by 2527

Abstract

A novel thiol-functionalized polysilsesqioxane containing hydroxyl and methyl groups was synthesized using a simple acid-catalyzed sol–gel method to develop an epoxy hardener with low odor, low volatile organic compound (VOC) emissions, and fast curing at low temperatures. The synthesized thiol-based hardeners were characterized [...] Read more.

A novel thiol-functionalized polysilsesqioxane containing hydroxyl and methyl groups was synthesized using a simple acid-catalyzed sol–gel method to develop an epoxy hardener with low odor, low volatile organic compound (VOC) emissions, and fast curing at low temperatures. The synthesized thiol-based hardeners were characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis (TGA), and gel permeation chromatography and compared with commercially available hardeners in terms of odor intensity and VOC emissions using the air dilution olfaction method and VOC analysis. The curing behavior and thermal and mechanical properties of the epoxy compounds prepared with the synthesized thiol-based hardeners were also evaluated. The results showed that synthetic thiol-based hardeners containing methyl and hydroxyl groups initiated the curing reaction of epoxy compounds at 53 °C and 45 °C, respectively. In contrast, commercial thiol-based hardeners initiated the curing reaction at 67 °C. Additionally, epoxy compounds with methyl-containing synthetic thiol-based hardeners exhibited higher TGA at a 5% weight loss temperature (>50 °C) and lap shear strength (20%) than those of the epoxy compounds with commercial thiol-based hardeners. Full article

(This article belongs to the Special Issue Research and Application of Polymer Adhesives)

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Polymers, Volume 15, Issue 13 (July-1 2023) – 220 articles

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