Polymers

20 pages, 3584 KiB

Open AccessArticle

Study on Adsorption Characteristics and Water Retention Properties of Attapulgite–Sodium Polyacrylate and Polyacrylamide to Trace Metal Cadmium Ion

by Ziming Cai, Feng Zhan, Yingnan Wang, Meiling Wu, Lingjian Kong, An Wang and Zhanbin Huang

Polymers 2024, 16(12), 1756; https://doi.org/10.3390/polym16121756 - 20 Jun 2024

Viewed by 1098

Abstract

The adsorption mechanism of superabsorbent polymer (SAP) can provide theoretical guidance for their practical applications in different environments. However, there has been limited research on the mechanism of attapulgite–sodium polyacrylate. This research aimed to compare the Cd(II) adsorption characteristics and water retention properties [...] Read more.

The adsorption mechanism of superabsorbent polymer (SAP) can provide theoretical guidance for their practical applications in different environments. However, there has been limited research on the mechanism of attapulgite–sodium polyacrylate. This research aimed to compare the Cd(II) adsorption characteristics and water retention properties of organic–inorganic composite SAP (attapulgite–sodium polyacrylate, OSAP) and organic SAP (polyacrylamide, JSAP). Batch experiments were used to investigate the kinetics of Cd(II) adsorption, as well as the thermodynamic properties and factors influencing these properties. The results show that the Cd(II) adsorption capacity was directly proportional to the pH value. The maximum adsorption capacities of OSAP and JSAP were of 770 and 345 mg·g⁻¹. The Cd(II) adsorption for OSAP and JSAP conformed to the Langmuir and the quasi-second-order kinetic model. This indicates that chemical adsorption is the primary mechanism. The adsorption process was endothermic (ΔH₀ > 0) and spontaneous (ΔG₀ < 0). The water adsorption ratios of OSAP and SAP were 474.8 and 152.6 in pure water. The ratio decreases with the increase in Cd(II) concentration. OSAP and JSAP retained 67.23% and 38.37% of the initial water adsorption after six iterations of water adsorption. Hence, OSAP is more suitable than JSAP for agricultural and environmental ecological restoration in arid and semi-arid regions. Full article

(This article belongs to the Section Polymer Analysis and Characterization)

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10 pages, 2275 KiB

Open AccessArticle

Molecular Dynamics Simulation of Silicone Oil Polymerization from Combined QM/MM Modeling

by Pascal Puhlmann and Dirk Zahn

Polymers 2024, 16(12), 1755; https://doi.org/10.3390/polym16121755 - 20 Jun 2024

Cited by 1 | Viewed by 1187

Abstract

We outline a molecular simulation protocol for elucidating the formation of silicone oil from trimethlyl- and dimethlysilanediole precursor mixtures. While the fundamental condensation reactions are effectively described by quantum mechanical calculations, this is combined with molecular mechanics models in order to assess the [...] Read more.

We outline a molecular simulation protocol for elucidating the formation of silicone oil from trimethlyl- and dimethlysilanediole precursor mixtures. While the fundamental condensation reactions are effectively described by quantum mechanical calculations, this is combined with molecular mechanics models in order to assess the extended relaxation processes. Within a small series of different precursor mixtures used as starting points, we demonstrate the evolution of the curing degree and heat formation in the course of polymer chain growth. Despite the increasing complexity of the amorphous agglomerate of polymer chains, our approach shows an appealing performance for tackling both elastic and viscous relaxation. Indeed, the finally obtained polymer systems feature 99% curing and thus offer realistic insights into the growth mechanisms of coexisting/competing polymer strands. Full article

(This article belongs to the Special Issue Molecular Dynamics Simulation of Polymeric Materials)

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Polymerization of PDMS by condensation reactions. In our simulation protocol, the gas phase reaction for k = m = 1 (and imposing vaporization of the formed water molecule) is used as the QM subsystem, whereas all other degrees of freedom are treated from MM calculations. Full article ">Figure 2
Comparison of the structure of hexamethyldisilane as obtained from dimerization of TMS. The atomic positions resulting from the MM model are shown as solid spheres (Si: yellow; O: red; C: gray; H: white), whereas the QM structure is indicated by a transparent ball and stick representation. Full article ">Figure 3
Interplay of curing degree and relaxation times needed as observed for a typical polymerization run. Left: evolution of the acceptance probability of the individual polymerization steps as a function of η. Right: curing degree as a function of the cumulative sum of reaction attempts needed. For comparison, the dashed curves shown in green indicate an idealized scenario in which all reaction attempts are successful. The solid curves shown in blue, black, and red refer to averages taken from three independent runs each performed at 250, 300, and 350 K, respectively, whereas the root-mean-square deviations are indicated by transparent color representations. Full article ">Figure 4
Curing of PDMS at 300 K and 1 atm using 3D periodic simulation cells. Starting from 500 DMSD precursor species, curing up to η = 99% is achieved, leading to a density increase from 0.91 g/cm3 to 1.04 g/cm3, respectively. Only Si atoms are shown. In the final system, a siloxane chain of 54 DMSD building blocks is highlighted in blue. To illustrate the formation process via reactions of monomers and oligomers, the same coloring is applied to earlier stages of polymerization. Full article ">Figure 5
Distribution of PDMS chain length as functions of (a) curing degree, (b) process temperature, and (c) precursor composition. The mean chain length (ν) is averaged from three independent polymerization runs. From the root-mean-square deviations we assess the polydispersity index (PDI = Mw/Mn) as PDI = 1.73/1.49/1.59 and PDI = 1.49/1.60/1.91, as functions of temperature (T = 250/300/350 K and 100% DMSD precursors) and composition (0/10/20% TMS and T = 300 K), respectively. Full article ">Figure 6
Heat of individual reaction steps as observed during the curing of PDMS. Data are shown for various DMSD/TMS precursor mixtures, all cured at 300 K and 1 atm, respectively. The curves shown in black refer to averages taken from three independent runs, whereas the root-mean-square deviations are indicated in gray. Left to right: profiles sampled for 0/10/20% TMS content, respectively, showing rough constant reaction heat (<ΔH>0<η<70% = 0.26/0.25/0.26 eV, as indicated by the dashed lines) up to η < 70%. Upon curing by 99%, the reaction heat is gradually reduced by about 0.1 eV because of the mechanical strain within the (amorphous) agglomerates of PDMS chains. The overall heat of formation is sampled as <ΔH>0<η<99% = 0.24/0.24/0.24 eV per monomeric unit for the silicone oils prepared from DMSD/TMS precursor mixtures of 0/10/20% TMS content, respectively. Full article ">Figure 7
Characterization of the finally obtained silicone oil models from curing the precursor systems of 0/10/20% TMS content at 300 K and 1 atm. Left: radial distribution functions of the Si-O distances. Right: mean-squared-deviation profiles as function of time as used for assessing the diffusion constants. For the latter, linear fits are applied to the last 7 ns, as indicated by the dashed lines. Full article ">

19 pages, 4178 KiB

Open AccessEditor’s ChoiceArticle

Cross-Scale Industrial Manufacturing of Multifunctional Glass Fiber/Epoxy Composite Tubes via a Purposely Modified Filament Winding Production Line

by George Karalis, Lampros Koutsotolis, Angelos Voudouris Itksaras, Thomai Tiriakidi, Nikolaos Tiriakidis, Kosmas Tiriakidis and Alkiviadis S. Paipetis

Polymers 2024, 16(12), 1754; https://doi.org/10.3390/polym16121754 - 20 Jun 2024

Viewed by 1132

Abstract

In the present research work is demonstrated a cross-scale manufacturing approach for the production of multifunctional glass fiber reinforced polymer (GFRP) composite tubes with a purposely redesigned filament winding process. Up until now, limited studies have been reported towards the multiscale reinforcement direction [...] Read more.

In the present research work is demonstrated a cross-scale manufacturing approach for the production of multifunctional glass fiber reinforced polymer (GFRP) composite tubes with a purposely redesigned filament winding process. Up until now, limited studies have been reported towards the multiscale reinforcement direction of continuous fibers for the manufacturing of hierarchical composites at the industrial level. This study involved the development of two different multi-walled carbon nanotube (MWCNT) aqueous-based inks, which were employed for the modification of commercial glass fiber (GF) reinforcing tows via a bath coating unit in a pilot production line. The obtained multifunctional GFRP tubes presented a variety of characteristics in relation to their final mechanical, hydrothermal aging, electrical, thermal and thermoelectric properties. Results revealed that the two individual systems exhibited pronounced differences both in crushing behavior and durability performance. Interestingly, for lateral compression the MWCNT coatings comprising a polymeric dispersant minorly affected the mechanical response of the produced tubes. The crashworthiness indicators of the multifunctional tubes displayed a slight 5% variation to the respective reference values, combined with a more ductile behavior. Moreover, regarding the bulk electrical and thermal conductivity values, as well as the Seebeck coefficient factor, the corresponding tubes displayed a variance of 233% and 19% and an opposite semi-conducting sign denoting a p- and n-type character, respectively. Full article

(This article belongs to the Special Issue Smart and Intelligent Composite Structures for Innovative Industrial and Space Applications: Fiber-Reinforced Polymer Composites)

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12 pages, 7233 KiB

Open AccessArticle

Additive Manufacturing of Head Surrogates for Evaluation of Protection in Sports

by Ramiro Mantecón, Borja Valverde-Marcos, Ignacio Rubio, George Youssef, José Antonio Loya, José Díaz-Álvarez and María Henar Miguélez

Polymers 2024, 16(12), 1753; https://doi.org/10.3390/polym16121753 - 20 Jun 2024

Viewed by 1193

Abstract

Head impacts are a major concern in contact sports and sports with high-speed mobility due to the prevalence of head trauma events and their dire consequences. Surrogates of human heads are required in laboratory testing to safely explore the efficacy of impact-mitigating mechanisms. [...] Read more.

Head impacts are a major concern in contact sports and sports with high-speed mobility due to the prevalence of head trauma events and their dire consequences. Surrogates of human heads are required in laboratory testing to safely explore the efficacy of impact-mitigating mechanisms. This work proposes using polymer additive manufacturing technologies to obtain a substitute for the human skull to be filled with a silicone-based brain surrogate. This assembly was instrumentalized with an Inertial Measurement Unit. Its performance was compared to a standard Hybrid III head form in validation tests using commercial headgear. The tests involved impact velocities in a range centered around 5 m/s. The results show a reasonable homology between the head substitutes, with a disparity in the impact response within 20% between the proposed surrogate and the standard head form. The head surrogate herein developed can be easily adapted to other morphologies and will significantly decrease the cost of the laboratory testing of head protection equipment, all while ensuring the safety of the testing process. Full article

(This article belongs to the Special Issue Polymers Additive Manufacturing in Sports and Protective Equipment)

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(A) Reference CT scan. (B) Segmented CAD model with only the skull of the cranial vault. (C) Layout of half-skull for 3D printing. (D) Geometry and attributes of the trilayer structure. Full article ">Figure 2
Assembly of demonstrators with cycling helmets of (A) Hybrid III and (B) surrogate in the drop tower. Full article ">Figure 3
Sensorization of the head forms and location of the accelerometers in (A) the 3D-printed head surrogate and (B) the Hybrid III. Full article ">Figure 4
Calibration curves for the Hybrid III head form (blue) and the 3D-printed head surrogate (red). Full article ">Figure 5
Acceleration–time histories as a function of drop height and velocities using cyclist helmet–Hybrid III testing construct. Shaded region is the time interval that maximizes the value of the HIC. Full article ">Figure 6
Acceleration–time curves were measured by dropping a 3D-printed, silicone-filled head surrogate fitted with a cyclist helmet at different velocities. Shaded region is the time interval that maximizes the value of the HIC. Full article ">Figure 7
Impact response of the two head forms represented by peak linear acceleration as a function of impact velocity. Datapoints are highlighted in circles. Full article ">

21 pages, 1474 KiB

Open AccessArticle

A Multi-Objective Optimization of Neural Networks for Predicting the Physical Properties of Textile Polymer Composite Materials

by Ivan Malashin, Vadim Tynchenko, Andrei Gantimurov, Vladimir Nelyub and Aleksei Borodulin

Polymers 2024, 16(12), 1752; https://doi.org/10.3390/polym16121752 - 20 Jun 2024

Cited by 2 | Viewed by 1346

Abstract

This paper explores the application of multi-objective optimization techniques, including MOPSO, NSGA II, and SPEA2, to optimize the hyperparameters of artificial neural networks (ANNs) and support vector machines (SVMs) for predicting the physical properties of textile polymer composite materials (TPCMs). The optimization process [...] Read more.

This paper explores the application of multi-objective optimization techniques, including MOPSO, NSGA II, and SPEA2, to optimize the hyperparameters of artificial neural networks (ANNs) and support vector machines (SVMs) for predicting the physical properties of textile polymer composite materials (TPCMs). The optimization process utilizes data on the physical characteristics of the constituent fibers and fabrics used to manufacture these composites. By employing optimization algorithms, we aim to enhance the predictive accuracy of the ANN and SVM models, thereby facilitating the design and development of high-performance textile polymer composites. The effectiveness of the proposed approach is demonstrated through comparative analyses and validation experiments, highlighting its potential for optimizing complex material systems. Full article

(This article belongs to the Special Issue Scientific Machine Learning for Polymeric Materials)

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14 pages, 4995 KiB

Open AccessArticle

Laser-Sintering of Cyclic Olefine Copolymer for Low Dielectric Loss Applications

by Manuel Romeis, Michael Ehrngruber and Dietmar Drummer

Polymers 2024, 16(12), 1751; https://doi.org/10.3390/polym16121751 - 20 Jun 2024

Viewed by 1214

Abstract

With increasing demands for data transfer, the production of components with low dielectric loss is crucial for the development of advanced antennas, which are needed to meet the requirements of next-generation communication technologies. This study investigates the impact of a variation in energy [...] Read more.

With increasing demands for data transfer, the production of components with low dielectric loss is crucial for the development of advanced antennas, which are needed to meet the requirements of next-generation communication technologies. This study investigates the impact of a variation in energy density on the part properties of a low-loss cyclic olefin copolymer (COC) in the SLS process as a way to manufacture complex low-dielectric-loss structures. Through a systematic variation in the laser energy, its impact on the part density, geometric accuracy, surface quality, and dielectric properties of the fabricated parts is assessed. This study demonstrates notable improvements in material handling and the quality of the manufactured parts while also identifying areas for further enhancement, particularly in mitigating thermo-oxidative aging. This research not only underscores the potential of COC in the realm of additive manufacturing but also sets the stage for future studies aimed at optimizing process parameters and enhancing material formulations to overcome current limitations. Full article

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

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23 pages, 2968 KiB

Open AccessReview

Valorization of Grain and Oil By-Products with Special Focus on Hemicellulose Modification

by Xiaoxian Liu, Jin Xie, Nicolas Jacquet and Christophe Blecker

Polymers 2024, 16(12), 1750; https://doi.org/10.3390/polym16121750 - 20 Jun 2024

Viewed by 1034

Abstract

Hemicellulose is one of the most important natural polysaccharides in nature. Hemicellulose from different sources varies in chemical composition and structure, which in turn affects the modification effects and industrial applications. Grain and oil by-products (GOBPs) are important raw materials for hemicellulose. This [...] Read more.

Hemicellulose is one of the most important natural polysaccharides in nature. Hemicellulose from different sources varies in chemical composition and structure, which in turn affects the modification effects and industrial applications. Grain and oil by-products (GOBPs) are important raw materials for hemicellulose. This article reviews the modification methods of hemicellulose in GOBPs. The effects of chemical and physical modification methods on the properties of GOBP hemicellulose biomaterials are evaluated. The potential applications of modified GOBP hemicellulose are discussed, including its use in film production, hydrogel formation, three-dimensional (3D) printing materials, and adsorbents for environmental remediation. The limitations and future recommendations are also proposed to provide theoretical foundations and technical support for the efficient utilization of these by-products. Full article

(This article belongs to the Section Polymer Applications)

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Representative chemical structures of hemicellulose ((A): Grasses, (B): Hardwood, (C): Softwood). Full article ">Figure 2
The etherification of hemicellulose ((A): Carboxymethylation, (B): Methylation, (C): Benzylation, (D): Quaternization). Full article ">Figure 3
The esterification of hemicellulose. Full article ">Figure 4
Using two α-arabinofuranosidases to remove α-arabinofuranose from wheat xylan [<a href="#B76-polymers-16-01750" class="html-bibr">76</a>]. Copyright 2024. Reproduced with permission from the American Chemical Society. Full article ">Figure 5
The synergistic enhancement of sodium alginate composite films by corn husk cellulose and hemicellulose [<a href="#B89-polymers-16-01750" class="html-bibr">89</a>]. Copyright 2024. Reproduced with permission from the Elsevier. Full article ">Figure 6
Construction of fully bio-based hydrogels using cellulose nanocrystals and arabinoxylan (CNC: cellulose nanocrystals, AX: arabinoxylan) [<a href="#B104-polymers-16-01750" class="html-bibr">104</a>]. Copyright 2024. Reproduced with permission from the American Chemical Society. Full article ">Figure 7
Synthesis of hemicellulose-co-PAAc hydrogels via radical copolymerization [<a href="#B105-polymers-16-01750" class="html-bibr">105</a>]. Copyright 2024. Reproduced with permission from the Elsevier. Full article ">Figure 8
Laccase-induced cross-linking of xylan [<a href="#B51-polymers-16-01750" class="html-bibr">51</a>]. Copyright 2024. Reproduced with permission from the Elsevier. Full article ">

16 pages, 16387 KiB

Open AccessArticle

Process Characterizations of Ultrasonic Extruded Weld-Riveting of AZ31B Magnesium Alloy to Carbon Fiber-Reinforced PA66

by Zeguang Liu, Guanxiong Lu, Yuanduo Yang, Sansan Ao, Kaifeng Wang and Yang Li

Polymers 2024, 16(12), 1749; https://doi.org/10.3390/polym16121749 - 20 Jun 2024

Cited by 2 | Viewed by 943

Abstract

Traditional metal–plastic dissimilar welding methods directly heat the metal workpiece, which may cause potential thermal damage to the metal workpiece. Ultrasonic extruded weld-riveting (UEWR) is a relatively new method for dissimilar joining of carbon fiber-reinforced thermoplastic (CFRTP) and metal. In this method, the [...] Read more.

Traditional metal–plastic dissimilar welding methods directly heat the metal workpiece, which may cause potential thermal damage to the metal workpiece. Ultrasonic extruded weld-riveting (UEWR) is a relatively new method for dissimilar joining of carbon fiber-reinforced thermoplastic (CFRTP) and metal. In this method, the CFRTP workpiece is melted using the ultrasonic effect and is squeezed into prefabricated holes in the metal workpiece to form a rivet structure. In this method, the metal workpiece is not directly heated, and potential high-temperature losses can be avoided. This paper investigates the process characterizations of UERW of AZ31B magnesium alloy to carbon fiber-reinforced PA66. The process parameters are optimized by the Taguchi method. The joint formation process is analyzed based on the fiber distribution in the cross-sections of joints. The effects of welding parameters on the joint microstructure and fracture surface morphology are discussed. The results show that a stepped amplitude strategy (40 μm amplitude in the first stage and 56 μm amplitude in the second stage) could balance the joint strength and joint appearance. Insufficient (welding energy < 2600 J or amplitude-A < 50%) or excessive (welding energy > 2800 J or amplitude-A > 50%) welding parameters lead to the formation of porous defects. Three fracture modes are identified according to the fracture surface analysis. The maximum tensile shear strength of joints at the optimal parameters is about 56.5 ± 6.2 MPa. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Polymer Blends and Composites)

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16 pages, 2636 KiB

Open AccessArticle

Characterization of a Delivery System Based on a Hyaluronic Acid 3D Scaffold and Gelatin Microparticles

by Cristina Martínez-Ramos, Alejandro Rodríguez Ruiz, Manuel Monleón Pradas and Fernando Gisbert Roca

Polymers 2024, 16(12), 1748; https://doi.org/10.3390/polym16121748 - 20 Jun 2024

Viewed by 4063

Abstract

The objective of this study was to develop and characterize a novel hyaluronic acid (HA) 3D scaffold integrated with gelatin microparticles for sustained-delivery applications. To achieve this goal, the delivery microparticles were synthesized and thoroughly characterized, focusing on their crosslinking mechanisms (vanillin and [...] Read more.

The objective of this study was to develop and characterize a novel hyaluronic acid (HA) 3D scaffold integrated with gelatin microparticles for sustained-delivery applications. To achieve this goal, the delivery microparticles were synthesized and thoroughly characterized, focusing on their crosslinking mechanisms (vanillin and genipin), degradation profiles, and release kinetics. Additionally, the cytotoxicity of the system was assessed, and its impact on the cell adhesion and distribution using mouse fibroblasts was examined. The combination of both biomaterials offers a novel platform for the gradual release of various factors encapsulated within the microparticles while simultaneously providing cell protection, support, and controlled factor dispersion due to the HA 3D scaffold matrix. Hence, this system offers a platform for addressing injure repair by continuously releasing specific encapsulated factors for optimal tissue regeneration. Additionally, by leveraging the properties of HA conjugates with small drug molecules, we can enhance the solubility, targeting capabilities, and cellular absorption, as well as prolong the system stability and half-life. As a result, this integrated approach presents a versatile strategy for therapeutic interventions aimed at promoting tissue repair and regeneration. Full article

(This article belongs to the Section Biobased and Biodegradable Polymers)

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SEM and fluorescence microscope images of the combined structure. SEM was used to study the structure of the HA scaffold with the gelatin microparticles crosslinked with genipin (images (A–D)) at 5×, 30×, 600×, and 2000×, respectively. Images (E,F) show the distribution of gelatin microparticles crosslinked with genipin and loaded with BSA-FITC in the HA scaffold once vacuum-injected at 10× and 20×, respectively. Full article ">Figure 2
SEM images of the gelatin microparticles. SEM was used to image the dry morphologies of gelatin microparticles before crosslinking (A) and after crosslinking with vanilin (B) and genipin (C). Full article ">Figure 3
Release of BSA and diffusion coefficients of microparticles. Percentage of BSA released in the 3 studied groups of microparticles: without crosslinking, crosslinked with genipin, and crosslinked with vanilin. A linear stage is observed during the first 4–5 h, followed by a saturation phase, as the group of microparticles crosslinked with genipin is the one that released the greatest amount of BSA. Full article ">Figure 4
Degradation study of microparticles. SEM pictures of the microparticle morphologies without crosslinking (A), crosslinked with vanilin (B), and crosslinked with genipin (C), showing less degradation on the genipin-crosslinked microparticles. Degradation of microparticles after 24, 72, and 144 h (D), confirming the lesser degradation of the genipin-crosslinked microparticles. Statistically significant differences are indicated by *** and ****, indicating p-values below 0.001 and 0.0001, respectively. Full article ">Figure 5
Cell viabilities via MTT assay after 24 h, 48 h, and 72 h. Cytotoxicity by indirect contact (extracts) of the negative control (NC), positive control (PC), and genipin-crosslinked gelatin microspheres on HA scaffold (HA–gelatin) using mouse fibroblast cells (L929). If the cell viability of the sample is >70%, the material shall be considered non-cytotoxic (dotted line). Statistically significant differences are indicated by *, *** and ****, indicating p-values below 0.05, 0.001 and 0.0001, respectively. Full article ">Figure 6
Confocal and scanning electron microscope (SEM) images of L929 cells cultured for 7 days on the system. In the confocal images (A,B), the attachment of the L929 cells to the scaffold of HA with gelatin microparticles crosslinked with genipin can be observed. In the SEM images (C,D), micrographs of fibroblasts cultured on the system are observed, showing the complete cell coverage of the HA scaffold with gelatin microparticles. Full article ">

18 pages, 9168 KiB

Open AccessArticle

Dual-Mode Ce-MOF Nanozymes for Rapid and Selective Detection of Hydrogen Sulfide in Aquatic Products

by Qi Cheng, Xiaoyu Du, Zuyao Fu, Zhaoyang Ding and Jing Xie

Polymers 2024, 16(12), 1747; https://doi.org/10.3390/polym16121747 - 20 Jun 2024

Cited by 1 | Viewed by 1503

Abstract

Increasing concern over the safety of consumable products, particularly aquatic products, due to freshness issues, has become a pressing issue. Therefore, ensuring the quality and safety of aquatic products is paramount. To address this, a dual-mode colorimetric–fluorescence sensor utilizing Ce-MOF as a mimic [...] Read more.

Increasing concern over the safety of consumable products, particularly aquatic products, due to freshness issues, has become a pressing issue. Therefore, ensuring the quality and safety of aquatic products is paramount. To address this, a dual-mode colorimetric–fluorescence sensor utilizing Ce-MOF as a mimic peroxidase to detect H₂S was developed. Ce-MOF was prepared by a conventional solvothermal synthesis method. Ce-MOF catalyzed the oxidation of 3,3’,5,5’-tetramethylbenzidine (TMB) by hydrogen peroxide (H₂O₂) to produce blue oxidized TMB (oxTMB). When dissolved, hydrogen sulfide (H₂S) was present in the solution, and it inhibited the catalytic effect of Ce-MOF and caused the color of the solution to fade from blue to colorless. This change provided an intuitive indication for the detection of H₂S. Through steady-state dynamic analysis, the working mechanism of this sensor was elucidated. The sensor exhibited pronounced color changes from blue to colorless, accompanied by a shift in fluorescence from none to light blue. Additionally, UV–vis absorption demonstrated a linear correlation with the H₂S concentration, ranging from 200 to 2300 µM, with high sensitivity (limit of detection, LOD = 0.262 μM). Fluorescence intensity also showed a linear correlation, ranging from 16 to 320 µM, with high selectivity and sensitivity (LOD = 0.156 μM). These results underscore the sensor’s effectiveness in detecting H₂S. Furthermore, the sensor enhanced the accuracy of H₂S detection and fulfilled the requirements for assessing food freshness and safety. Full article

(This article belongs to the Special Issue Application of Metal-Organic Frameworks Based on Polymers)

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22 pages, 5171 KiB

Open AccessArticle

Flash Pyrolysis of Waste Tires in an Entrained Flow Reactor—An Experimental Study

by Balan Ramani, Arqam Anjum, Eddy Bramer, Wilma Dierkes, Anke Blume and Gerrit Brem

Polymers 2024, 16(12), 1746; https://doi.org/10.3390/polym16121746 - 20 Jun 2024

Cited by 1 | Viewed by 2027

Abstract

In this study, a flash pyrolysis process is developed using an entrained flow reactor for recycling of waste tires. The flash pyrolysis system is tested for process stability and reproducibility of the products under similar operating conditions when operated continuously. The study is [...] Read more.

In this study, a flash pyrolysis process is developed using an entrained flow reactor for recycling of waste tires. The flash pyrolysis system is tested for process stability and reproducibility of the products under similar operating conditions when operated continuously. The study is performed with two different feedstock materials, i.e., passenger car (PCT) and truck tire (TT) granulates, to understand the influence of feedstock on the yield and properties of the pyrolysis products. The different pyrolytic products i.e., pyrolytic carbon black (pCB), oil, and pyro-gas, are analyzed, and their key properties are discussed. The potential applications for the obtained pyrolytic products are discussed. Finally, a mass and energy balance analysis has been performed for the developed pyrolysis process. The study provides insight into the governing mechanisms of the flash pyrolysis process for waste tires, which is useful to optimize the process depending on the desired applications for the pyrolysis products, and also to scale up the pyrolysis process. Full article

(This article belongs to the Special Issue Recycling of Plastic and Rubber Wastes)

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12 pages, 916 KiB

Open AccessArticle

Development of a Biopolymer-Based Anti-Fog Coating with Sealing Properties for Applications in the Food Packaging Sector

by Masoud Ghaani, Maral Soltanzadeh, Daniele Carullo and Stefano Farris

Polymers 2024, 16(12), 1745; https://doi.org/10.3390/polym16121745 - 20 Jun 2024

Viewed by 1563

Abstract

The quest for sustainable and functional food packaging materials has led researchers to explore biopolymers such as pullulan, which has emerged as a notable candidate for its excellent film-forming and anti-fogging properties. This study introduces an innovative anti-fog coating by combining pullulan with [...] Read more.

The quest for sustainable and functional food packaging materials has led researchers to explore biopolymers such as pullulan, which has emerged as a notable candidate for its excellent film-forming and anti-fogging properties. This study introduces an innovative anti-fog coating by combining pullulan with poly (acrylic acid sodium salt) to enhance the display of packaged food in high humidity environments without impairing the sealing performance of the packaging material—two critical factors in preserving food quality and consumers’ acceptance. The research focused on varying the ratios of pullulan to poly (acrylic acid sodium salt) and investigating the performance of this formulation as an anti-fog coating on bioriented polypropylene (BOPP). Contact angle analysis showed a significant improvement in BOPP wettability after coating deposition, with water contact angle values ranging from ~60° to ~17° for formulations consisting only of poly (acrylic acid sodium salt) (P0) or pullulan (P100), respectively. Furthermore, seal strength evaluations demonstrated acceptable performance, with the optimal formulation (P50) achieving the highest sealing force (~2.7 N/2.5 cm) at higher temperatures (130 °C). These results highlight the exceptional potential of a pullulan-based coating as an alternative to conventional packaging materials, significantly enhancing anti-fogging performance. Full article

(This article belongs to the Special Issue Development and Application of Bio-Based Polymers)

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20 pages, 10437 KiB

Open AccessArticle

The Seed Germination Test as a Valuable Tool for the Short-Term Phytotoxicity Screening of Water-Soluble Polyamidoamines

by Elisabetta Ranucci, Sofia Treccani, Paolo Ferruti and Jenny Alongi

Polymers 2024, 16(12), 1744; https://doi.org/10.3390/polym16121744 - 19 Jun 2024

Cited by 1 | Viewed by 1534

Abstract

Six differently charged amphoteric polyamidoamines, synthesized by the polyaddition of N,N′-methylenebisacrylamide to alanine, leucine, serine, arginine (M-ARG), glutamic acid (M-GLU) and a glycine/cystine mixture, were screened for their short-term phytotoxicity using a seed germination test. Lepidium sativum L. seeds were [...] Read more.

Six differently charged amphoteric polyamidoamines, synthesized by the polyaddition of N,N′-methylenebisacrylamide to alanine, leucine, serine, arginine (M-ARG), glutamic acid (M-GLU) and a glycine/cystine mixture, were screened for their short-term phytotoxicity using a seed germination test. Lepidium sativum L. seeds were incubated in polyamidoamine water solutions with concentrations ranging from 0.156 to 2.5 mg mL⁻¹ at 25 ± 1 °C for 120 h. The seed germination percentage (SG%), an indicator of acute toxicity, and both root and shoot elongation, related to plant maturation, were the considered endpoints. The germination index (GI) was calculated as the product of relative seed germination times relative radical growth. The SG% values were in all cases comparable to those obtained in water, indicating no detectable acute phytotoxicity of the polyamidoamines. In the short term, the predominantly positively charged M-ARG proved to be phytotoxic at all concentrations (GI < 0.8), whereas the predominantly negatively charged M-GLU proved to be biostimulating at intermediate concentrations (GI > 1) and slightly inhibitory at 2.5 mg mL⁻¹ (0.8 < GI < 1). Overall, polyamidoamine phytotoxicity could be correlated to charge distribution, demonstrating the potential of the test for predicting and interpreting the eco-toxicological behavior of water-soluble polyelectrolytes. Full article

(This article belongs to the Section Polymer Applications)

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19 pages, 5651 KiB

Open AccessArticle

Advanced Dentistry Biomaterials Containing Graphene Oxide

by Doina Prodan, Marioara Moldovan, Stanca Cuc, Codruţa Sarosi, Ioan Petean, Miuța Filip, Rahela Carpa, Rami Doukeh and Ioana-Codruta Mirica

Polymers 2024, 16(12), 1743; https://doi.org/10.3390/polym16121743 - 19 Jun 2024

Viewed by 1172

Abstract

The aim of this study was to obtain three experimental resin-based cements containing GO and HA-Ag for posterior restorations. The samples (S0, S1, and S2) shared the same polymer matrix (BisGMA, TEGDMA) and powder mixture (bioglass (La₂O₃ and Sr-Zr), quartz, [...] Read more.

The aim of this study was to obtain three experimental resin-based cements containing GO and HA-Ag for posterior restorations. The samples (S0, S1, and S2) shared the same polymer matrix (BisGMA, TEGDMA) and powder mixture (bioglass (La₂O₃ and Sr-Zr), quartz, GO, and HA-Ag), with different percentages of graphene oxide (0%, 0.1%, 0.2% GO) and silver-doped hydroxyapatite (10%, 9.9%, 9.8% HA-Ag). The physical–chemical properties (water absorption, degree of conversion), mechanical properties (DTS, CS, FS), structural properties (SEM, AFM), and antibacterial properties (Staphylococcus aureus, Enterococcus faecalis, Streptococcus mutans, Porphyromonas gingivalis, and Escherichia coli) were investigated. The results showed that the mechanical properties, except for the diametral tensile test, increased with the rise in the %GO. After 28 days, water absorption increased with the rise in the %GO. The surface structure of the samples did not show major changes after water absorption for 28 days. The antibacterial effects varied depending on the samples and bacterial strains tested. After increasing the %GO and decreasing the %HA-Ag, we observed a more pronounced antibacterial effect. The presence of GO, even in very small percentages, improved the properties of the tested experimental cements. Full article

(This article belongs to the Special Issue Functional Graphene-Polymer Composites)

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16 pages, 4487 KiB

Open AccessArticle

An Oxalato-Bridged Cu(II)-Based 1D Polymer Chain: Synthesis, Structure, and Adsorption of Organic Dyes

by Fouzia Munawar, Muhammad Khalid, Muhammad Imran, Muhammad Naveed Qasim, Shazia Waseem, Murad A. AlDamen, Muhammad Ashfaq, Muhammad Imran and Muhammad Nadeem Akhtar

Polymers 2024, 16(12), 1742; https://doi.org/10.3390/polym16121742 - 19 Jun 2024

Cited by 1 | Viewed by 932

Abstract

In the current research, we prepared a polymeric framework, {[Cu(C₂O₄)(C₁₀H₈N₂)]·H₂O·0.67(CH₃OH)]}_n (1) (where C₂O₄ = oxalic acid; C₁₀H₈N₂ = [...] Read more.

In the current research, we prepared a polymeric framework, {[Cu(C₂O₄)(C₁₀H₈N₂)]·H₂O·0.67(CH₃OH)]}_n (1) (where C₂O₄ = oxalic acid; C₁₀H₈N₂ = 2,2-bipyridine), and explored this compound for adsorption of methylene blue (MB) and methyl orange (MO). The crystal structure of the compound consists of a Cu(ox)(bpy) unit connected via oxalate to form a 1D polymeric chain. This polymeric chain has adsorption capacities of 194.0 and 167.3 mg/g for MB and MO, respectively. The removal rate is estimated to be 77.6% and 66.9% for MB and MO, respectively. The plausible mechanisms for adsorption are electrostatic, π-π interaction, and OH-π interaction for dye stickiness. The adsorbent surface exhibits a negative charge that produces the electrostatic interaction, resulting in excellent adsorption efficiency at pH 7 and 8. The pseudo-first-order kinetic model is selected for the adsorption of MB and MO on the adsorbent. The reported compound has remarkable efficiency for sorption of organic dyes and can be useful in wastewater treatment. Full article

(This article belongs to the Section Polymer Chemistry)

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17 pages, 6621 KiB

Open AccessArticle

New Fire-Retardant Open-Cell Composite Polyurethane Foams Based on Triphenyl Phosphate and Natural Nanoscale Additives

by Kirill Cherednichenko, Egor Smirnov, Maria Rubtsova, Dmitrii Repin and Anton Semenov

Polymers 2024, 16(12), 1741; https://doi.org/10.3390/polym16121741 - 19 Jun 2024

Cited by 1 | Viewed by 1191

Abstract

Despite the mechanical and physical properties of polyurethane foams (PUF), their application is still hindered by high inflammability. The elaboration of effective, low-cost, and environmentally friendly fire retardants remains a pressing issue that must be addressed. This work aims to show the feasibility [...] Read more.

Despite the mechanical and physical properties of polyurethane foams (PUF), their application is still hindered by high inflammability. The elaboration of effective, low-cost, and environmentally friendly fire retardants remains a pressing issue that must be addressed. This work aims to show the feasibility of the successful application of natural nanomaterials, such as halloysite nanotubes and nanocellulose, as promising additives to the commercial halogen-free, fire-retardant triphenyl phosphate (TPP) to enhance the flame retardance of open-cell polyurethane foams. The nanocomposite foams were synthesized by in situ polymerization. Investigation of the mechanical properties of the nanocomposite PUF revealed that the nanoscale additives led to a notable decrease in the foam’s compressibility. The obtained results of the flammability tests clearly indicate that there is a prominent synergetic effect between the fire-retardant and the natural nanoscale additives. The nanocomposite foams containing a mixture of TPP (10 and 20 parts per hundred polyol by weight) and either 10 wt.% of nanocellulose or 20 wt.% of halloysite demonstrated the lowest burning rate without dripping and were rated as HB materials according to UL 94 classification. Full article

(This article belongs to the Special Issue Advances in Functional Polyurethane and Composites)

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SEM micrographs, elemental mapping and the corresponding EDS spectrum of PUF/20HNT (A), PUF/20TPP (B), and PUF/20TPP/20HNT (C). Full article ">Figure 2
The photos of the cross sections, apparent densities, and box-plots of the cell area of PUF/TPP/HNT and PUF/TPP/NC. Full article ">Figure 3
(A) FTIR spectra of individual HNT, TPP, reference PUF, PUF/20TPP, PUF/20HNT, and PUF/20TPP/20HNT; (B) FTIR spectra of individual NC, TPP, reference PUF, PUF/20TPP, PUF/20NC, and PUF/20TPP/20NC. The red, blue, and green dashed zones indicate the presence of TPP, HNT, and NC bands in the FTIR spectra of the final nanocomposite PUF samples, respectively. Full article ">Figure 4
Results of compression force deflection measurements for the reference PUF, PUF modified with 10 php and 20 php of TPP and nanocomposite PUF: (A) PUF/10TPP/HNT and PUF/20TPP/HNT, (B) PUF/10TPP/NC and PUF/20TPP/NC. Full article ">Figure 5
dTG curves of reference PUF, single TPP, PUF modified with 10 php and 20 php of TPP, and nanocomposite PUF: (A) PUF/TPP10/HNT, (B) PUF/TPP20/HNT, (C) PUF/TPP10/NC, and (D) PUF/TPP20/NC. Full article ">Figure 6
Burning rates of PUF/TPP/HNT (A) and PUF/TPP/NC (B) in comparison with reference PUF, foams modified with 10 and 20 php of TPP and 10 and 20 wt.% of HNT and NC. The horizontal dashed line represents burning rate of 40 mm/min, which corresponds to HB class. Full article ">Figure 7
SEM micrographs of char layer and the corresponding EDS spectra of PUF/20HNT, PUF/20NC, PUF/20TPP, PUF/20TPP/20HNT, and PUF/20TPP/20NC. The zones of sample analyzed at higher magnification and zones of EDS analysis are marked by green and red, respectively. Full article ">

15 pages, 9036 KiB

Open AccessReview

Substrate Neutrality for Obtaining Block Copolymer Vertical Orientation

by Kaitlyn Hillery, Nayanathara Hendeniya, Shaghayegh Abtahi, Caden Chittick and Boyce Chang

Polymers 2024, 16(12), 1740; https://doi.org/10.3390/polym16121740 - 19 Jun 2024

Viewed by 1218

Abstract

Nanopatterning methods utilizing block copolymer (BCP) self-assembly are attractive for semiconductor fabrication due to their molecular precision and high resolution. Grafted polymer brushes play a crucial role in providing a neutral surface conducive for the orientational control of BCPs. These brushes create a [...] Read more.

Nanopatterning methods utilizing block copolymer (BCP) self-assembly are attractive for semiconductor fabrication due to their molecular precision and high resolution. Grafted polymer brushes play a crucial role in providing a neutral surface conducive for the orientational control of BCPs. These brushes create a non-preferential substrate, allowing wetting of the distinct chemistries from each block of the BCP. This vertically aligns the BCP self-assembled lattice to create patterns that are useful for semiconductor nanofabrication. In this review, we aim to explore various methods used to tune the substrate and BCP interface toward a neutral template. This review takes a historical perspective on the polymer brush methods developed to achieve substrate neutrality. We divide the approaches into copolymer and blended homopolymer methods. Early attempts to obtain neutral substrates utilized end-grafted random copolymers that consisted of monomers from each block. This evolved into side-group-grafted chains, cross-linked mats, and block cooligomer brushes. Amidst the augmentation of the chain architecture, homopolymer blends were developed as a facile method where polymer chains with each chemistry were mixed and grafted onto the substrate. This was largely believed to be challenging due to the macrophase separation of the chemically incompatible chains. However, innovative methods such as sequential grafting and BCP compatibilizers were utilized to circumvent this problem. The advantages and challenges of each method are discussed in the context of neutrality and feasibility. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)

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21 pages, 13283 KiB

Open AccessArticle

Quantitative Analysis of Morphology and Surface Properties of Poly(lactic acid)/Poly(ε-caprolactone)/Hydrophilic Nano-Silica Blends

by Sanja Mahović Poljaček, Dino Priselac, Tamara Tomašegović, Mirela Leskovac, Aleš Šoster and Urška Stanković Elesini

Polymers 2024, 16(12), 1739; https://doi.org/10.3390/polym16121739 - 19 Jun 2024

Viewed by 1213

Abstract

A quantitative analysis of the morphology, as well as an analysis of the distribution of components and surface/interfacial properties in poly(lactic acid)(PLA) InegoTM 3251D, poly(ε-caprolactone) (PCL) Capa 6800 and nano-silica (SiO₂) Aerosil^®200 blends, was conducted in this research. The [...] Read more.

A quantitative analysis of the morphology, as well as an analysis of the distribution of components and surface/interfacial properties in poly(lactic acid)(PLA) InegoTM 3251D, poly(ε-caprolactone) (PCL) Capa 6800 and nano-silica (SiO₂) Aerosil^®200 blends, was conducted in this research. The study aimed to improve the understanding of how PLA, PCL, and nano-SiO₂ interact, resulting in the specific morphology and surface properties of the blends. Samples were produced by varying the concentration of all three components. They were analyzed using SEM, EDS mapping, water contact angle measurements, surface free energy calculation, adhesion parameter measurements, and FTIR-ATR spectroscopy. The results showed that the addition of SiO₂ nanoparticles led to an increase in the contact angle of water, making the surface more hydrophobic. SEM images of the blends showed that increasing the PCL content reduced the size of spherical PCL elements in the blends. FTIR-ATR analysis showed that SiO₂ nanoparticles influenced the structure ordering of PLA in the blend with equal portions of PLA and PCL. In the samples with a higher PCL content, the spherical elements present in the samples with a higher PLA/PCL ratio have been reduced, indicating better interactions at the interface between PLA, PCL, and SiO₂. SEM-EDS mapping of the PLA/PCL 100/0 blend surfaces revealed the presence of SiO₂ clusters and the silicon (Si) concentration reaching up to ten times higher than the nominal concentration of SiO₂. However, with the addition of 3% SiO₂ to the blend containing PCL, the structure became more granular. Specifically, Si protrusions in the sample PLA/PCL 90/10 with 3% SiO₂ displayed 29.25% of Si, and the sample PLA/PCL 70/30 with 3% SiO₂ displayed an average of 10.61% of Si at the protrusion locations. The results confirmed the affinity of SiO₂ to be encapsulated by PCL. A better understanding of the interactions between the materials in the presented blends and the quantitative analysis of their morphology could improve the understanding of their properties and allow the optimization of their application for different purposes. Full article

(This article belongs to the Special Issue Advanced Polymer Blends: From Processing to Characterisation and Application)

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21 pages, 6224 KiB

Open AccessArticle

Hybrid Zinc Phthalocyanine/PVDF-HFP System for Reducing Biofouling in Water Desalination: DFT Theoretical and MolDock Investigations

by Bassem Jamoussi, Mohhamed Naif M. Al-Sharif, Lassaad Gzara, Hussam Organji, Talal B. Almeelbi, Radhouane Chakroun, Bandar A. Al-Mur, Naief H. M. Al Makishah, Mohamed H. F. Madkour, Fahed A. Aloufi and Riyadh F. Halawani

Polymers 2024, 16(12), 1738; https://doi.org/10.3390/polym16121738 - 19 Jun 2024

Viewed by 1681

Abstract

Fouling and biofouling remain significant challenges in seawater desalination plants. One practical approach to address these issues is to develop anti-biofouling membranes. Therefore, novel hybrid zinc phthalocyanine/polyvinylidene fluoride-co-hexafluoropropylene (Zn(4-PPOx)₄Pc/PVDF-HFP) membranes were prepared by electrospinning to evaluate their properties against biofouling. The [...] Read more.

Fouling and biofouling remain significant challenges in seawater desalination plants. One practical approach to address these issues is to develop anti-biofouling membranes. Therefore, novel hybrid zinc phthalocyanine/polyvinylidene fluoride-co-hexafluoropropylene (Zn(4-PPOx)₄Pc/PVDF-HFP) membranes were prepared by electrospinning to evaluate their properties against biofouling. The hybrid nanofiber membrane was characterized by atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and contact angle measurements. The theoretical calculations of PVDF-HFP, Zn(4-PPOx)₄Pc), and Zn(4-PPOx)₄Pc/PVDF-HFP nanofibers were performed using a hybrid functional RB3LYP and the 6-31 G (d,p) basis set, employing Gaussian 09. DFT calculations illustrated that the calculated physical and electronic parameters ensured the feasibility of the interaction of PVDF-HFP with Zn(4-PPOx)₄Pc via a halogen–hydrogen bond, resulting in a highly stable and remarkably reactive structure. Moreover, molecular electrostatic potential (MEP) maps were drawn to identify the reactive regions of the Zn(4-PPOx)4Pc and PVDF-HFP/Zn(4-PPOx)4Pc nanofibers. Molecular docking analysis revealed that Zn(4-PPOx)₄Pc has highest binding affinity (−8.56 kcal/mol) with protein from S. aureus (1N67) mainly with ten amino acids (ASP405, LYS374, GLU446, ASN406, ALA441, TYR372, LYS371, TYR448, LYS374, and ALA442). These findings highlight the promising potential of Zn(4-PPOx) ₄Pc/PVDF-HFP nanocomposite membranes in improving the efficiency of water desalination by reducing biofouling and providing antibacterial properties. Full article

(This article belongs to the Special Issue Advanced Polymer Materials for Water and Wastewater Treatment)

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2 pages, 617 KiB

Open AccessCorrection

Correction: Zanchetta et al. Effects of Electrospun Fibrous Membranes of PolyCaprolactone and Chitosan/Poly(Ethylene Oxide) on Mouse Acute Skin Lesions. Polymers 2020, 12, 1580

by Flávia Cristina Zanchetta, Rafael Bergamo Trinca, Juliany Lino Gomes Silva, Jéssica da Silva Cunha Breder, Thiago Anselmo Cantarutti, Sílvio Roberto Consonni, Ângela Maria Moraes, Eliana Pereira de Araújo, Mario José Abdalla Saad, Gary G. Adams and Maria Helena Melo Lima

Polymers 2024, 16(12), 1737; https://doi.org/10.3390/polym16121737 - 19 Jun 2024

Viewed by 2744

Abstract

In the original publication, the authors claimed that Figure 6 reporting Western blot data was erroneous as published [...] Full article

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15 pages, 2880 KiB

Open AccessArticle

Hydrophilization and Functionalization of Fullerene C₆₀ with Maleic Acid Copolymers by Forming a Non-Covalent Complex

by Nadezhda A. Samoilova, Maria A. Krayukhina, Zinaida S. Klemenkova, Alexander V. Naumkin, Michail I. Buzin, Yaroslav O. Mezhuev, Evgeniy A. Turetsky, Sergey M. Andreev, Nelya M. Anuchina and Dmitry A. Popov

Polymers 2024, 16(12), 1736; https://doi.org/10.3390/polym16121736 - 19 Jun 2024

Viewed by 1589

Abstract

In this study, we report an easy approach for the production of aqueous dispersions of C₆₀ fullerene with good stability. Maleic acid copolymers, poly(styrene-alt-maleic acid) (SM), poly(N-vinyl-2-pyrrolidone-alt-maleic acid) (VM) and poly(ethylene-alt-maleic acid) (EM) were used to [...] Read more.

In this study, we report an easy approach for the production of aqueous dispersions of C₆₀ fullerene with good stability. Maleic acid copolymers, poly(styrene-alt-maleic acid) (SM), poly(N-vinyl-2-pyrrolidone-alt-maleic acid) (VM) and poly(ethylene-alt-maleic acid) (EM) were used to stabilize C₆₀ fullerene molecules in an aqueous environment by forming non-covalent complexes. Polymer conjugates were prepared by mixing a solution of fullerene in N-methylpyrrolidone (NMP) with an aqueous solution of the copolymer, followed by exhaustive dialysis against water. The molar ratios of maleic acid residues in the copolymer and C₆₀ were 5/1 for SM and VM and 10/1 for EM. The volume ratio of NMP and water used was 1:1.2–1.6. Water-soluble complexes (composites) dried lyophilically retained solubility in NMP and water but were practically insoluble in non-polar solvents. The optical and physical properties of the preparations were characterized by UV-Vis spectroscopy, FTIR, DLS, TGA and XPS. The average diameter of the composites in water was 120–200 nm, and the ξ-potential ranged from −16 to −20 mV. The bactericidal properties of the obtained nanostructures were studied. Toxic reagents and time-consuming procedures were not used in the preparation of water-soluble C₆₀ nanocomposites stabilized by the proposed copolymers. Full article

(This article belongs to the Special Issue Polymer-Containing Nanomaterials: Synthesis, Properties, Applications)

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Aqueous solutions and dry forms of polymer–fullerene samples: 1—C60/SM, 2—C60/EM, 3—C60/VM. Full article ">Figure 2
Absorption spectra of water solutions of copolymers and C60 conjugates: 1—EM, 2—SM, 3—VM; 4—C60/SM, 5—C60/VM, 6—C60/EM; (C = 80–90 μg/mL, l = 0.2 cm); 7—C60/VM after drying and dissolving (C = 100 μg/mL). Full article ">Figure 3
FTIR spectra of samples containing copolymers: (a) VM, (b) EM and (c) SM; initial copolymers (a1–c1) and fullerene conjugates (a2–c2). Full article ">Figure 3 Cont.
FTIR spectra of samples containing copolymers: (a) VM, (b) EM and (c) SM; initial copolymers (a1–c1) and fullerene conjugates (a2–c2). Full article ">Figure 4
TGA curves of samples containing VM (a), EM (b) and SM (c) copolymers: 1—copolymers, 2—mechanical mixtures of copolymer with C60, 3—hybrid structures and 4—C60. Heating rate of 10 °C/min (argon atmosphere). Full article ">Figure 5
TGA curves: 1—C60 after dialysis and lyophilic drying, 2—pristine C60. Full article ">Figure 6
The high-resolution C 1s spectra normalized by the intensity of the main peak ((a) 1—C60/SM, 2—C60/EM, 3—C60/VM), sample C60/SM (b), sample C60/EM (c) and sample C60/VM (d). Black—experimental line, green—Gaussian profiles used for fitting, red—result of fitting. Full article ">

15 pages, 5650 KiB

Open AccessArticle

Crystallization Behavior and Mechanical Property of Biodegradable Poly(butylene succinate-co-2-methyl succinate)/Cellulose Nanocrystals Composites

by Wenxin Yao, Siyu Pan and Zhaobin Qiu

Polymers 2024, 16(12), 1735; https://doi.org/10.3390/polym16121735 - 19 Jun 2024

Cited by 1 | Viewed by 890

Abstract

Biodegradable poly(butylene succinate-co-2-methyl succinate) (PBSMS)/cellulose nanocrystals (CNC) composites were successfully prepared at low CNC loadings with the aims of improving crystallization and mechanical properties and extending the practical application of PBSMS. CNC is finely dispersed in the PBSMS matrix without obvious [...] Read more.

Biodegradable poly(butylene succinate-co-2-methyl succinate) (PBSMS)/cellulose nanocrystals (CNC) composites were successfully prepared at low CNC loadings with the aims of improving crystallization and mechanical properties and extending the practical application of PBSMS. CNC is finely dispersed in the PBSMS matrix without obvious aggregations. The low content of CNC obviously promoted the crystallization behavior of PBSMS under different conditions. The spherulitic morphology study revealed that CNC, as an effective heterogeneous nucleating agent, provided more nucleation sites during the melt crystallization process. In addition, the nucleation effect of CNC was quantitatively evaluated by the following two parameters, i.e., nucleation activity and nucleation efficiency. The crystal structure and crystallization mechanism of PBSMS remained unchanged in the composites. In addition, as a reinforcing nanofiller, CNC significantly increased Young’s modulus and the yield strength of PBSMS. The crystallization behavior and mechanical properties of PBSMS were significantly improved by the low content of CNC, which should be interesting and essential from the perspective of biodegradable polymer composites. Full article

(This article belongs to the Special Issue Sustainable Bio-Based and Circular Polymers and Composites)

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22 pages, 5195 KiB

Open AccessArticle

Xanthan–Polyurethane Conjugates: An Efficient Approach for Drug Delivery

by Narcis Anghel, Iuliana Spiridon, Maria-Valentina Dinu, Stelian Vlad and Mihaela Pertea

Polymers 2024, 16(12), 1734; https://doi.org/10.3390/polym16121734 - 19 Jun 2024

Viewed by 1046

Abstract

The antifungal agent, ketoconazole, and the anti-inflammatory drug, piroxicam, were incorporated into matrices of xanthan or oleic acid-esterified xanthan (Xn) and polyurethane (PU), to develop topical drug delivery systems. Compared to matrices without bioactive compounds, which only showed a nominal compressive stress of [...] Read more.

The antifungal agent, ketoconazole, and the anti-inflammatory drug, piroxicam, were incorporated into matrices of xanthan or oleic acid-esterified xanthan (Xn) and polyurethane (PU), to develop topical drug delivery systems. Compared to matrices without bioactive compounds, which only showed a nominal compressive stress of 32.18 kPa (sample xanthan–polyurethane) at a strain of 71.26%, the compressive resilience of the biomaterials increased to nearly 50.04 kPa (sample xanthan–polyurethane–ketoconazole) at a strain of 71.34%. The compressive strength decreased to around 30.67 kPa upon encapsulating a second drug within the xanthan–polyurethane framework (sample xanthan–polyurethane–piroxicam/ketoconazole), while the peak sustainable strain increased to 87.21%. The Weibull model provided the most suitable fit for the drug release kinetics. Unlike the materials based on xanthan–polyurethane, those made with oleic acid-esterified xanthan–polyurethane released the active ingredients more slowly (the release rate constant showed lower values). All the materials demonstrated antimicrobial effectiveness. Furthermore, a higher volume of piroxicam was released from oleic acid-esterified xanthan–polyurethane–piroxicam (64%) as compared to xanthan–polyurethane–piroxicam (44%). Considering these results, materials that include polyurethane and either modified or unmodified xanthan showed promise as topical drug delivery systems for releasing piroxicam and ketoconazole. Full article

(This article belongs to the Special Issue Progress in Polymer Networks)

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15 pages, 8343 KiB

Open AccessArticle

Structural Behavior of High Durability FRP Helical Screw Piles Installed in Reclaimed Saline Land

by Sun-Hee Kim, Hyung-Joong Joo and Wonchang Choi

Polymers 2024, 16(12), 1733; https://doi.org/10.3390/polym16121733 - 19 Jun 2024

Viewed by 1024

Abstract

The bearing capacity of fiber-reinforced plastic (FRP) helical screw piles is determined by the lesser of the breaking load at the bolted joint and the resistance provided by the screw tip area. In this study, compression and tensile tests were performed with the [...] Read more.

The bearing capacity of fiber-reinforced plastic (FRP) helical screw piles is determined by the lesser of the breaking load at the bolted joint and the resistance provided by the screw tip area. In this study, compression and tensile tests were performed with the number of bolts and edge distance as variables. It showed similar strength when compared to the failure stress derived from material testing. In addition, considering load resistance performance, the optimal screw cross section was obtained through parametric analysis. Considering the structural behavior of the screw, a prediction equation was presented to design the screw cross-section as a tapered cross-section using a theoretical method. As a result of comparing the screw cross-section with the finite element analysis results, it was confirmed that the design stress and analysis stress showed an error of 1.1 MPa and were within the allowable stress of 80 MPa. Full article

(This article belongs to the Special Issue Advances in Reinforced Polymer Materials for Additive Manufacturing, Product Design, Processing and Their Applications)

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12 pages, 3569 KiB

Open AccessArticle

Preparation and Evaluation of PVDF-HFP-Based Gel Electrolyte for Ge-Sensitized Thermal Cell

by Yadong Chai and Sachiko Matsushita

Polymers 2024, 16(12), 1732; https://doi.org/10.3390/polym16121732 - 18 Jun 2024

Viewed by 2275

Abstract

The semiconductor-sensitized thermal cell (STC) is a new thermoelectric conversion technology. The development of nonliquid electrolytes is the top priority for the practical application of the STC. In this study, a novel gel polymer electrolyte (PH-based GPE) composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PH), [...] Read more.

The semiconductor-sensitized thermal cell (STC) is a new thermoelectric conversion technology. The development of nonliquid electrolytes is the top priority for the practical application of the STC. In this study, a novel gel polymer electrolyte (PH-based GPE) composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PH), 1-Methyl-2-pyrrolidone (NMP), and Cu ions was synthesized and applied to the STC system. The PH-based GPE synthesized at 45 °C showed higher open-circuit voltage (−0.3 V), short-circuit current density (59 μA cm⁻²) and diffusion coefficient (7.82 × 10⁻¹² m² s⁻¹), indicating that a well-balanced structure among the NMP molecules was formed to generate a high-efficiency conduction path of the Cu ions. Moreover, the ion diffusion lengths decreased with decreasing content rates of NMP for the PH-based GPEs, indicating that the NMP plays an important role in the diffusion of Cu ions. Furthermore, the activation energy was calculated to be 107 kJ mol⁻¹, and that was smaller compared to 150 kJ mol⁻¹ for the poly(ethylene glycol)-based liquid electrolyte. These results play an important reference role in the development of electrolytes for STC systems. At the same time, they also provide a new avenue and reference indicator for the synthesis of high-performance and safe GPEs. Full article

(This article belongs to the Special Issue Polymers for Environmental Remediation and Energy Regeneration)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
(a) Illustration of the cell assembly procedure and (b) digital camera image of the assembled cell. Full article ">Figure 2
FT-IR spectra of (PVDF-HFP) PH, NMP, PH-NMP, NMP-Cu, and PH-NMP-Cu. Full article ">Figure 3
(a–g) Digital camera images of the fabricated cells and (h–n) microphotographs of the electrolytes observed from FTO side at different gelation temperatures ((a,h) 30 °C, (b,i) 35 °C, (c,j) 40 °C, (d,k) 45 °C, (e,l) 50 °C, (f,m) 55 °C, and (g,n) 60 °C). Full article ">Figure 4
(a) FT-IR spectra and (b) content rates of NMP for the electrolytes at different gelation temperatures, where A1 is the absorption band due to C=O stretching vibration of NMP and A2 is the absorption band due to CF2 stretching vibration of PVDF-HFP. Full article ">Figure 5
(a) Cyclic voltammetry and (c) chronoamperometry of the cells measured at different temperatures which are equal to the gelation temperatures. (b) Open−circuit voltages, short−circuit current densities, and (d) discharge times of the cells are obtained from CV and CP measurements. Full article ">

13 pages, 2093 KiB

Open AccessArticle

An Approach to a Silver Conductive Ink for Inkjet Printer Technology

by Svetlana N. Kholuiskaya, Valentina Siracusa, Gulnaz M. Mukhametova, Luybov A. Wasserman, Vladislav V. Kovalenko and Alexey L. Iordanskii

Polymers 2024, 16(12), 1731; https://doi.org/10.3390/polym16121731 - 18 Jun 2024

Cited by 1 | Viewed by 1677

Abstract

Silver-based metal–organic decomposition inks composed of silver salts, complexing agents and volatile solvents are now the subject of much research due to the simplicity and variability of their preparation, their high stability and their relatively low sintering temperature. The use of this type [...] Read more.

Silver-based metal–organic decomposition inks composed of silver salts, complexing agents and volatile solvents are now the subject of much research due to the simplicity and variability of their preparation, their high stability and their relatively low sintering temperature. The use of this type of ink in inkjet printing allows for improved cost-effective and environmentally friendly technology for the production of electrical devices, including flexible electronics. An approach to producing a silver salt-based reactive ink for jet printing has been developed. The test images were printed with an inkjet printer onto polyimide substrates, and two-stage thermal sintering was carried out at temperatures of 60 °C and 100–180 °C. The structure and electrical properties of the obtained conductive lines were investigated. As a result, under optimal conditions an electrically conductive film with low surface resistance of approximately 3 Ω/square can be formed. Full article

(This article belongs to the Special Issue Applications of 3D Printing for Polymers, 3rd Edition)

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16 pages, 6329 KiB

Open AccessArticle

Investigation of Recycled Expanded Polyamide Beads through Artificial Ageing and Mechanical Recycling as a Proof of Concept for Circular Economy

by Sören Handtke, Lena Brömstrup, Jörg Hain, Fabian Fischer, Tim Ossowski, Sven Hartwig and Klaus Dröder

Polymers 2024, 16(12), 1730; https://doi.org/10.3390/polym16121730 - 18 Jun 2024

Cited by 1 | Viewed by 1238

Abstract

Car manufacturers are currently challenged with increasing the sustainability of their products and production to comply with sustainability requirements and legislation. One way to enhance product sustainability is by reducing the carbon footprint of fossil-based plastic parts. Particle foams are a promising solution [...] Read more.

Car manufacturers are currently challenged with increasing the sustainability of their products and production to comply with sustainability requirements and legislation. One way to enhance product sustainability is by reducing the carbon footprint of fossil-based plastic parts. Particle foams are a promising solution to achieve the goal of using lightweight parts with minimal material input. Ongoing developments involve the use of expanded particle foam beads made from engineering plastics such as polyamide (EPA). To achieve this, a simulated life cycle was carried out on virgin EPA, including mechanical recycling. The virgin material was processed into specimens using a steam-free method. One series was artificially aged to replicate automotive life cycle stresses, while the other series was not. The mechanical recycling and re-foaming of the minipellets were then carried out, resulting in an EPA particle foam with 100% recycled content. Finally, the thermal and chemical material properties were comparatively analysed. The study shows that the recycled EPA beads underwent polymer degradation during the simulated life cycle, as evidenced by their material properties. For instance, the recycled beads showed a more heterogeneous molecular weight distribution (an increase in PDI from two to three), contained carbonyl groups, and exhibited an increase in the degree of crystallization from approximately 24% to 36%. Full article

(This article belongs to the Special Issue Thermoplastic Foams: Processing, Manufacturing, and Characterization)

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18 pages, 6495 KiB

Open AccessArticle

Antibacterial Potential and Biocompatibility of Chitosan/Polycaprolactone Nanofibrous Membranes Incorporated with Silver Nanoparticles

by Viktoriia Korniienko, Yevgeniia Husak, Kateryna Diedkova, Yuliia Varava, Vladlens Grebnevs, Oksana Pogorielova, Māris Bērtiņš, Valeriia Korniienko, Baiba Zandersone, Almira Ramanaviciene, Arunas Ramanavicius and Maksym Pogorielov

Polymers 2024, 16(12), 1729; https://doi.org/10.3390/polym16121729 - 18 Jun 2024

Cited by 7 | Viewed by 1710

Abstract

This study addresses the need for enhanced antimicrobial properties of electrospun membranes, either through surface modifications or the incorporation of antimicrobial agents, which are crucial for improved clinical outcomes. In this context, chitosan—a biopolymer lauded for its biocompatibility and extracellular matrix-mimicking properties—emerges as [...] Read more.

This study addresses the need for enhanced antimicrobial properties of electrospun membranes, either through surface modifications or the incorporation of antimicrobial agents, which are crucial for improved clinical outcomes. In this context, chitosan—a biopolymer lauded for its biocompatibility and extracellular matrix-mimicking properties—emerges as an excellent candidate for tissue regeneration. However, fabricating chitosan nanofibers via electrospinning often challenges the preservation of their structural integrity. This research innovatively develops a chitosan/polycaprolactone (CH/PCL) composite nanofibrous membrane by employing a layer-by-layer electrospinning technique, enhanced with silver nanoparticles (AgNPs) synthesized through a wet chemical process. The antibacterial efficacy, adhesive properties, and cytotoxicity of electrospun chitosan membranes were evaluated, while also analyzing their hydrophilicity and nanofibrous structure using SEM. The resulting CH/PCL-AgNPs composite membranes retain a porous framework, achieve balanced hydrophilicity, display commendable biocompatibility, and exert broad-spectrum antibacterial activity against both Gram-negative and Gram-positive bacteria, with their efficacy correlating to the AgNP concentration. Furthermore, our data suggest that the antimicrobial efficiency of these membranes is influenced by the timed release of silver ions during the incubation period. Membranes incorporated starting with AgNPs at a concentration of 50 µg/mL effectively suppressed the growth of both microorganisms during the early stages up to 8 h of incubation. These insights underscore the potential of the developed electrospun composite membranes, with their superior antibacterial qualities, to serve as innovative solutions in the field of tissue engineering. Full article

(This article belongs to the Special Issue Bio-Inspired Polymers: Synthesis, Properties and Applications)

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10 pages, 1098 KiB

Open AccessArticle

Piezoelectric Outputs of Electrospun PVDF Web as Full-Textile Sensor at Different Mechanical Excitation Frequencies

by Fenye Meng and Jiyong Hu

Polymers 2024, 16(12), 1728; https://doi.org/10.3390/polym16121728 - 18 Jun 2024

Viewed by 1031

Abstract

With the increasing application of electrospun PVDF webs in piezoelectric sensors and energy-harvesting devices, it is crucial to understand their responses under complex mechanical excitations. However, the dependence of the piezoelectric effect on mechanical excitation properties is not fully comprehended. This study aims [...] Read more.

With the increasing application of electrospun PVDF webs in piezoelectric sensors and energy-harvesting devices, it is crucial to understand their responses under complex mechanical excitations. However, the dependence of the piezoelectric effect on mechanical excitation properties is not fully comprehended. This study aims to investigate the piezoelectric output of randomly oriented electrospun PVDF nanofiber webs fabricated through different electrospinning processes at various mechanical excitation frequencies. The electrospun PVDF web was sandwiched between two textile electrodes, and its piezoelectric output as a full-textile sensor was measured across a frequency range from 0.1 Hz to 10 Hz. The experimental results revealed that the piezoelectric output of the electrospun PVDF web exhibited a nearly linear increase at excitation frequencies below 1.0 Hz and then reached an almost constant value thereafter up to 10 Hz, which is different from the hybrid PVDF or its copolymer web. Furthermore, the dependency of the piezoelectric output on the excitation frequency was found to be influenced by the specific electrospinning process employed, which determined the crystalline structure of electrospun PVDF nanofibers. These findings suggest that determining an appropriate working frequency for randomly oriented electrospun PVDF nanofiber webs is essential before practical implementation, and the piezoelectric response mode in different mechanical activation frequency ranges can be used to detect different human physiological behaviors. Full article

(This article belongs to the Special Issue Polymer-Based Smart Textiles: Synthesis, Characterization and Application, 2nd Edition)

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19 pages, 9277 KiB

Open AccessArticle

Bioactivity and Antibacterial Analysis of Plasticized PLA Electrospun Fibers Reinforced with MgO and Mg(OH)₂ Nanoparticles

by Adrián Leonés, Valentina Salaris, Laura Peponi, Marcela Lieblich, Alexandra Muñoz-Bonilla, Marta Fernández-García and Daniel López

Polymers 2024, 16(12), 1727; https://doi.org/10.3390/polym16121727 - 18 Jun 2024

Cited by 3 | Viewed by 1305

Abstract

In this work, we focused on the bioactivity and antibacterial behavior of PLA-based electrospun fibers, efibers, reinforced with both MgO and Mg(OH)₂ nanoparticles, NPs. The evolution of PLA-based efibers was followed in terms of morphology, FTIR, XRD, and visual appearance. The bioactivity [...] Read more.

In this work, we focused on the bioactivity and antibacterial behavior of PLA-based electrospun fibers, efibers, reinforced with both MgO and Mg(OH)₂ nanoparticles, NPs. The evolution of PLA-based efibers was followed in terms of morphology, FTIR, XRD, and visual appearance. The bioactivity was discussed in terms of hydroxyapatite growth after 28 days, considered as T28, of immersion in simulated body fluid, SBF. In particular, the biomineralization process evidenced after immersion in SBF started at T14 in both systems. The number of precipitated crystals increased by increasing the amount of both NPs. The chemical composition of the precipitated crystals was also characterized in terms of the Ca/P molar ratio after T28 of immersion in SBF, indicating the presence of hydroxyapatite on the surface of both reinforced efibers. Moreover, a reduction in the average diameter of the PLA-based efibers was observed, reaching a maximum reduction of 46 and 60% in the average diameter of neat PLA and PLA:OLA efibers, respectively, after 28 days of immersion in SBF. The antibacterial behavior of the MgO and Mg(OH)₂ NPs in the PLA-based electrospun fibers was tested against Escherichia coli, E. coli, as the Gram-negative bacteria, and Staphylococcus aureus, S. aureus, as the Gram-positive bacteria, obtaining the best antibacterial activity against the Gram-negative bacteria E. coli of 21 ± 2% and 34 ± 6% for the highest concentration of MgO and Mg(OH)₂ NPs, respectively. Full article

(This article belongs to the Special Issue Organic-Inorganic Hybrid Materials III)

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SEM images of PLA and PLA:OLA efibers in SBF at T0, T14, and T28. Full article ">Figure 2
SEM images of PLA:OLA-MgO efibers in SBF at T0, T14, and T28. Full article ">Figure 3
SEM images of PLA:OLA-Mg(OH)2 efibers in SBF at T0, T14 and T28. Full article ">Figure 4
Diameter size distributions at T0 for the different electrospun fibers studied. Full article ">Figure 5
Average diameter evolution of PLA-based efibers in SBF at T0, T14, and T28 of (a) PLA:OLA-MgO and (b) PLA:OLA-Mg(OH)2 efibers. Full article ">Figure 6
XRD patterns of (a) PLA and PLA:OLA, (b) PLA:OLA-MgO, and (c) PLA:OLA-Mg(OH)2 efibers in SBF at T0 (left) and T28 (right). Full article ">Figure 7
FTIR spectra of (a) PLA:OLA-MgO and (b) PLA:OLA-Mg(OH)2 efibers after immersion in SBF at T0 and T28. Spectra of PLA and PLA:OLA are also included in the graphs. Full article ">Figure 8
FTIR spectra 1800–400 cm−1 of (a) PLA:OLA-MgO and (b) PLA:OLA-Mg(OH)2 efibers after immersion in SBF at T28. Spectra of PLA and PLA:OLA are also included in the graphs. Full article ">Figure 9
Images of the control plate and the plasticized PLA electrospun fiber at the highest concentrations of MgO and Mg(OH)2 NPs against (a) E. coli and (b) S. aureus. Full article ">

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Polymers, Volume 16, Issue 12 (June-2 2024) – 143 articles

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