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Polymers, Volume 15, Issue 5 (March-1 2023) – 267 articles

Cover Story (view full-size image): Nature-inspired actuators are used to carry out effective motions based on the flexibility of natural creatures. This study presents an actuator that can simulate the motion of an elephant's trunk in several degrees of freedom. Actuators made of soft polymers that actively respond to external stimuli were integrated with shape memory alloys (SMAs) to mimic the flexible body and muscles of an elephant's trunk. The intended actuator is a soft gripper that combines a flexible polymer and SMAs to mimic an elephant trunk's flexible and effective gripping action. View this paper
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19 pages, 5696 KiB  
Article
Synthesis of Calcium Peroxide Nanoparticles with Starch as a Stabilizer for the Degradation of Organic Dye in an Aqueous Solution
by Nurul Nazihah Amerhaider Nuar, Siti Nurul Ain Md. Jamil, Thomas Shean Yaw Choong, Intan Diana Mat Azmi, Nor Athirah Abdul Romli, Luqman Chuah Abdullah, Pen-Chi Chiang and Fan Li
Polymers 2023, 15(5), 1327; https://doi.org/10.3390/polym15051327 - 06 Mar 2023
Viewed by 2137
Abstract
One of the most significant environmental problems in the world is the massive release of dye wastewater from the dyeing industry. Therefore, the treatment of dyes effluents has received significant attention from researchers in recent years. Calcium peroxide (CP) from the group of [...] Read more.
One of the most significant environmental problems in the world is the massive release of dye wastewater from the dyeing industry. Therefore, the treatment of dyes effluents has received significant attention from researchers in recent years. Calcium peroxide (CP) from the group of alkaline earth metal peroxides acts as an oxidizing agent for the degradation of organic dyes in water. It is known that the commercially available CP has a relatively large particle size, which makes the reaction rate for pollution degradation relatively slow. Therefore, in this study, starch, a non-toxic, biodegradable and biocompatible biopolymer, was used as a stabilizer for synthesizing calcium peroxide nanoparticles (Starch@CPnps). The Starch@CPnps were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer–Emmet–Teller (BET), dynamic light scattering (DLS), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM). The degradation of organic dyes, methylene blue (MB), using Starch@CPnps as a novel oxidant was studied using three different parameters: initial pH of the MB solution, calcium peroxide initial dosage and contact time. The degradation of the MB dye was carried out via a Fenton reaction, and the degradation efficiency of Starch@CPnps was successfully achieved up to 99%. This study shows that the potential application of starch as a stabilizer can reduce the size of the nanoparticles as it prevents the agglomeration of the nanoparticles during synthesis. Full article
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18 pages, 4633 KiB  
Article
Geometric Analysis of Three-Dimensional Woven Fabric with in-Plane Auxetic Behavior
by Muhammad Zeeshan, Hong Hu and Ehsan Etemadi
Polymers 2023, 15(5), 1326; https://doi.org/10.3390/polym15051326 - 06 Mar 2023
Cited by 3 | Viewed by 1907
Abstract
Auxetic textiles are emerging as an enticing option for many advanced applications due to their unique deformation behavior under tensile loading. This study reports the geometrical analysis of three-dimensional (3D) auxetic woven structures based on semi-empirical equations. The 3D woven fabric was developed [...] Read more.
Auxetic textiles are emerging as an enticing option for many advanced applications due to their unique deformation behavior under tensile loading. This study reports the geometrical analysis of three-dimensional (3D) auxetic woven structures based on semi-empirical equations. The 3D woven fabric was developed with a special geometrical arrangement of warp (multi-filament polyester), binding (polyester-wrapped polyurethane), and weft yarns (polyester-wrapped polyurethane) to achieve an auxetic effect. The auxetic geometry, the unit cell resembling a re-entrant hexagon, was modeled at the micro-level in terms of the yarn’s parameters. The geometrical model was used to establish a relationship between the Poisson’s ratio (PR) and the tensile strain when it was stretched along the warp direction. For validation of the model, the experimental results of the developed woven fabrics were correlated with the calculated results from the geometrical analysis. It was found that the calculated results were in good agreement with the experimental results. After experimental validation, the model was used to calculate and discuss critical parameters that affect the auxetic behavior of the structure. Thus, geometrical analysis is believed to be helpful in predicting the auxetic behavior of 3D woven fabrics with different structural parameters. Full article
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16 pages, 6557 KiB  
Article
Crosslinking Rapidly Cured Epoxy Resin Thermosets: Experimental and Computational Modeling and Simulation Study
by Ahmed Al-Qatatsheh, Jaworski C. Capricho, Paolo Raiteri, Saulius Juodkazis, Nisa Salim and Nishar Hameed
Polymers 2023, 15(5), 1325; https://doi.org/10.3390/polym15051325 - 06 Mar 2023
Viewed by 1804
Abstract
The power of computational modeling and simulation for establishing clear links between materials’ intrinsic properties and their atomic structure has more and more increased the demand for reliable and reproducible protocols. Despite this increased demand, no one approach can provide reliable and reproducible [...] Read more.
The power of computational modeling and simulation for establishing clear links between materials’ intrinsic properties and their atomic structure has more and more increased the demand for reliable and reproducible protocols. Despite this increased demand, no one approach can provide reliable and reproducible outcomes to predict the properties of novel materials, particularly rapidly cured epoxy-resins with additives. This study introduces the first computational modeling and simulation protocol for crosslinking rapidly cured epoxy resin thermosets based on solvate ionic liquid (SIL). The protocol combines several modeling approaches, including quantum mechanics (QMs) and molecular dynamics (MDs). Furthermore, it insightfully provides a wide range of thermo-mechanical, chemical, and mechano-chemical properties, which agree with experimental data. Full article
(This article belongs to the Special Issue Recent Advances in Lightweight Fiber-Reinforced Polymer Composites)
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19 pages, 1319 KiB  
Article
Design of New Dispersants Using Machine Learning and Visual Analytics
by María Jimena Martínez, Roi Naveiro, Axel J. Soto, Pablo Talavante, Shin-Ho Kim Lee, Ramón Gómez Arrayas, Mario Franco, Pablo Mauleón, Héctor Lozano Ordóñez, Guillermo Revilla López, Marco Bernabei, Nuria E. Campillo and Ignacio Ponzoni
Polymers 2023, 15(5), 1324; https://doi.org/10.3390/polym15051324 - 06 Mar 2023
Cited by 3 | Viewed by 2119
Abstract
Artificial intelligence (AI) is an emerging technology that is revolutionizing the discovery of new materials. One key application of AI is virtual screening of chemical libraries, which enables the accelerated discovery of materials with desired properties. In this study, we developed computational models [...] Read more.
Artificial intelligence (AI) is an emerging technology that is revolutionizing the discovery of new materials. One key application of AI is virtual screening of chemical libraries, which enables the accelerated discovery of materials with desired properties. In this study, we developed computational models to predict the dispersancy efficiency of oil and lubricant additives, a critical property in their design that can be estimated through a quantity named blotter spot. We propose a comprehensive approach that combines machine learning techniques with visual analytics strategies in an interactive tool that supports domain experts’ decision-making. We evaluated the proposed models quantitatively and illustrated their benefits through a case study. Specifically, we analyzed a series of virtual polyisobutylene succinimide (PIBSI) molecules derived from a known reference substrate. Our best-performing probabilistic model was Bayesian Additive Regression Trees (BART), which achieved a mean absolute error of 5.50±0.34 and a root mean square error of 7.56±0.47, as estimated through 5-fold cross-validation. To facilitate future research, we have made the dataset, including the potential dispersants used for modeling, publicly available. Our approach can help accelerate the discovery of new oil and lubricant additives, and our interactive tool can aid domain experts in making informed decisions based on blotter spot and other key properties. Full article
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18 pages, 4384 KiB  
Article
Mass and Charge Transfer in a Polymeric NiSalen Complex at Subzero Temperatures
by Elena V. Alekseeva, Julia V. Novoselova, Dmitrii V. Anischenko, Vasiliy V. Potapenkov and Oleg V. Levin
Polymers 2023, 15(5), 1323; https://doi.org/10.3390/polym15051323 - 06 Mar 2023
Viewed by 1277
Abstract
Electrochemical energy storage systems have a wide range of commercial applications. They keep energy and power even at temperatures up to +60 °C. However, the capacity and power of such energy storage systems reduce sharply at negative temperatures due to the difficulty of [...] Read more.
Electrochemical energy storage systems have a wide range of commercial applications. They keep energy and power even at temperatures up to +60 °C. However, the capacity and power of such energy storage systems reduce sharply at negative temperatures due to the difficulty of counterion injection into the electrode material. The application of organic electrode materials based on salen-type polymers is a prospective approach to the development of materials for low-temperature energy sources. Poly[Ni(CH3Salen)]–based electrode materials synthesized from different electrolytes were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and quartz crystal microgravimetry at temperatures from −40 °C to 20 °C. By analyzing data obtained in various electrolyte solutions, it was shown that at subzero temperatures, the process of injection into the polymer film, together with slow diffusion within the film, predominantly limit the electrochemical performance of electrode materials based on poly[Ni(CH3Salen)]. It was shown that the deposition of the polymer from solutions with larger cations allow the enhancement of the charge transfer due to the formation of porous structures facilitating the counter-ion diffusion. Full article
(This article belongs to the Special Issue Polymers for Electronics and Photonics)
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16 pages, 2622 KiB  
Article
Poly(octamethylene citrate) Modified with Glutathione as a Promising Material for Vascular Tissue Engineering
by Agata Flis, Martina Trávníčková, Filip Koper, Karolina Knap, Wiktor Kasprzyk, Lucie Bačáková and Elżbieta Pamuła
Polymers 2023, 15(5), 1322; https://doi.org/10.3390/polym15051322 - 06 Mar 2023
Cited by 3 | Viewed by 1404
Abstract
One of the major goals of vascular tissue engineering is to develop much-needed materials that are suitable for use in small-diameter vascular grafts. Poly(1,8-octamethylene citrate) can be considered for manufacturing small blood vessel substitutes, as recent studies have demonstrated that this material is [...] Read more.
One of the major goals of vascular tissue engineering is to develop much-needed materials that are suitable for use in small-diameter vascular grafts. Poly(1,8-octamethylene citrate) can be considered for manufacturing small blood vessel substitutes, as recent studies have demonstrated that this material is cytocompatible with adipose tissue-derived stem cells (ASCs) and favors their adhesion and viability. The work presented here is focused on modifying this polymer with glutathione (GSH) in order to provide it with antioxidant properties, which are believed to reduce oxidative stress in blood vessels. Cross-linked poly(1,8-octamethylene citrate) (cPOC) was therefore prepared by polycondensation of citric acid and 1,8-octanediol at a 2:3 molar ratio of the reagents, followed by in-bulk modification with 0.4, 0.8, 4 or 8 wt.% of GSH and curing at 80 °C for 10 days. The chemical structure of the obtained samples was examined by FTIR-ATR spectroscopy, which confirmed the presence of GSH in the modified cPOC. The addition of GSH increased the water drop contact angle of the material surface and lowered the surface free energy values. The cytocompatibility of the modified cPOC was evaluated in direct contact with vascular smooth-muscle cells (VSMCs) and ASCs. The cell number, the cell spreading area and the cell aspect ratio were measured. The antioxidant potential of GSH-modified cPOC was measured by a free radical scavenging assay. The results of our investigation indicate the potential of cPOC modified with 0.4 and 0.8 wt.% of GSH to produce small-diameter blood vessels, as the material was found to: (i) have antioxidant properties, (ii) support VSMC and ASC viability and growth and (iii) provide an environment suitable for the initiation of cell differentiation. Full article
(This article belongs to the Special Issue Polymer Scaffolds for Tissue Engineering II)
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12 pages, 3199 KiB  
Article
Solvent-Evaporation-Induced Synthesis of Graphene Oxide/Peptide Nanofiber (GO/PNF) Hybrid Membranes Doped with Silver Nanoparticles for Antibacterial Application
by Peng He, Minghao Yang, Yu Lei, Lei Guo, Yan Wang and Gang Wei
Polymers 2023, 15(5), 1321; https://doi.org/10.3390/polym15051321 - 06 Mar 2023
Viewed by 1699
Abstract
Designing functional membranes through the collaboration of multi-dimensional nanomaterials is of particular interest in environmental and biomedical applications. Herein, we propose a facile and green synthetic strategy by collaborating with graphene oxide (GO), peptides, and silver nanoparticles (AgNPs) to synthesize functional hybrid membranes [...] Read more.
Designing functional membranes through the collaboration of multi-dimensional nanomaterials is of particular interest in environmental and biomedical applications. Herein, we propose a facile and green synthetic strategy by collaborating with graphene oxide (GO), peptides, and silver nanoparticles (AgNPs) to synthesize functional hybrid membranes with favourable antibacterial effects. GO nanosheets are functionalized with self-assembled peptide nanofibers (PNFs) to form GO/PNFs nanohybrids, in which the PNFs not only improve the biocompatibility and dispersity of GO, but also provide more active sites for growing and anchoring AgNPs. As a result, multifunctional GO/PNFs/AgNP hybrid membranes with adjustable thickness and AgNP density are prepared via the solvent evaporation technique. The structural morphology of the as-prepared membranes is characterized using scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy, and their properties are analyzed by spectral methods. The hybrid membranes are then subjected to antibacterial experiments and their excellent antibacterial performances are demonstrated. Full article
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12 pages, 3650 KiB  
Article
Additive Effects of Solid Paraffins on Mechanical Properties of High-Density Polyethylene
by Asae Ito, Akid Ropandi, Koichi Kono, Yusuke Hiejima and Koh-hei Nitta
Polymers 2023, 15(5), 1320; https://doi.org/10.3390/polym15051320 - 06 Mar 2023
Cited by 1 | Viewed by 1483
Abstract
In this work, two types of solid paraffins (i.e., linear and branched) were added to high-density polyethylene (HDPE) to investigate their effects on the dynamic viscoelasticity and tensile properties of HDPE. The linear and branched paraffins exhibited high and low crystallizability, respectively. The [...] Read more.
In this work, two types of solid paraffins (i.e., linear and branched) were added to high-density polyethylene (HDPE) to investigate their effects on the dynamic viscoelasticity and tensile properties of HDPE. The linear and branched paraffins exhibited high and low crystallizability, respectively. The spherulitic structure and crystalline lattice of HDPE are almost independent of the addition of these solid paraffins. The linear paraffin in the HDPE blends exhibited a melting point at 70 °C in addition to the melting point of HDPE, whereas the branched paraffins showed no melting point in the HDPE blend. Furthermore, the dynamic mechanical spectra of the HDPE/paraffin blends exhibited a novel relaxation between −50 °C and 0 °C, which was absent in HDPE. Adding linear paraffin toughened the stress–strain behavior of HDPE by forming crystallized domains in the HDPE matrix. In contrast, branched paraffins with lower crystallizability compared to linear paraffin softened the stress–strain behavior of HDPE by incorporating them into its amorphous layer. The mechanical properties of polyethylene-based polymeric materials were found to be controlled by selectively adding solid paraffins with different structural architectures and crystallinities. Full article
(This article belongs to the Section Polymer Physics and Theory)
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12 pages, 3497 KiB  
Article
Synthesis of Alginate Nanoparticles Using Hydrolyzed and Enzyme-Digested Alginate Using the Ionic Gelation and Water-in-Oil Emulsion Method
by Nicolas Van Bavel, Anna-Marie Lewrenz, Travis Issler, Liping Pang, Max Anikovskiy and Elmar J. Prenner
Polymers 2023, 15(5), 1319; https://doi.org/10.3390/polym15051319 - 06 Mar 2023
Cited by 1 | Viewed by 2553
Abstract
Alginate nanoparticles (AlgNPs) are attracting increasing interest for a range of applications because of their good biocompatibility and their ability to be functionalized. Alginate is an easily accessible biopolymer which is readily gelled by the addition of cations such as calcium, facilitating a [...] Read more.
Alginate nanoparticles (AlgNPs) are attracting increasing interest for a range of applications because of their good biocompatibility and their ability to be functionalized. Alginate is an easily accessible biopolymer which is readily gelled by the addition of cations such as calcium, facilitating a cost-effective and efficient production of nanoparticles. In this study, AlgNPs based on acid hydrolyzed and enzyme-digested alginate were synthesized by using ionic gelation and water-in-oil emulsification, with the goal to optimize key parameters to produce small uniform (<200 nm) AlgNPs. By the ionic gelation method, such AlgNPs were obtained when sample concentrations were 0.095 mg/mL for alginate and CaCl2 in the range of 0.03–0.10 mg/mL. Alginate and CaCl2 concentrations > 0.10 mg/mL resulted in sizes > 200 nm with relatively high dispersity. Sonication in lieu of magnetic stirring proved to further reduce size and increase homogeneity of the nanoparticles. In the water-in-oil emulsification method, nanoparticle growth was confined to inverse micelles in an oil phase, resulting in lower dispersity. Both the ionic gelation and water-in-oil emulsification methods were suitable for producing small uniform AlgNPs that can be further functionalized as required for various applications. Full article
(This article belongs to the Section Biomacromolecules, Biobased and Biodegradable Polymers)
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13 pages, 1821 KiB  
Article
Life Cycle Environmental Impacts of a Biobased Acrylic Polymer for Leather Production
by Olga Ballús, Meritxell Guix, Grau Baquero and Anna Bacardit
Polymers 2023, 15(5), 1318; https://doi.org/10.3390/polym15051318 - 06 Mar 2023
Cited by 1 | Viewed by 2254
Abstract
The aim of this paper was to develop a biopolymer based on raw materials not originating from petroleum chemistry to reduce the environmental impact. To this end, an acrylic-based retanning product was designed where part of the fossil-based raw materials was replaced with [...] Read more.
The aim of this paper was to develop a biopolymer based on raw materials not originating from petroleum chemistry to reduce the environmental impact. To this end, an acrylic-based retanning product was designed where part of the fossil-based raw materials was replaced with biomass-derived polysaccharides. Life cycle assessment (LCA) of the new biopolymer and a standard product was conducted to determine the environmental impact. Biodegradability of both products was determined by BOD5/COD ratio measurement. Products were characterized by IR, gel permeation chromatography (GPC), and Carbon-14 content. The new product was experimented as compared to standard fossil-based product, and the main properties of leathers and effluents were assessed. The results showed that the new biopolymer provides the leather with similar organoleptic characteristics, higher biodegradability and better exhaustion. LCA allowed concluding that the new biopolymer reduces the environmental impact of 4 of the 19 impact categories analyzed. A sensitivity analysis was performed where the polysaccharide derivative was replaced with a protein derivative. The analysis concluded that the protein-based biopolymer reduced the environmental impact in 16 of the 19 categories studied. Therefore, the choice of the biopolymer is critical in this type of products, which may or may not reduce the environmental impact. Full article
(This article belongs to the Section Polymer Networks)
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14 pages, 3299 KiB  
Article
Dislodgment Resistance, Adhesive Pattern, and Dentinal Tubule Penetration of a Novel Experimental Algin Biopolymer-Incorporated Bioceramic-Based Root Canal Sealer
by Galvin Sim Siang Lin, Norhayati Luddin, Huwaina Abd Ghani, Josephine Chang Hui Lai and Tahir Yusuf Noorani
Polymers 2023, 15(5), 1317; https://doi.org/10.3390/polym15051317 - 06 Mar 2023
Cited by 2 | Viewed by 1550
Abstract
The currently available bioceramic-based sealers still demonstrate low bond strength with a poor seal in root canal despite desirable biological properties. Hence, the present study aimed to determine the dislodgment resistance, adhesive pattern, and dentinal tubule penetration of a novel experimental algin-incorporated bioactive [...] Read more.
The currently available bioceramic-based sealers still demonstrate low bond strength with a poor seal in root canal despite desirable biological properties. Hence, the present study aimed to determine the dislodgment resistance, adhesive pattern, and dentinal tubule penetration of a novel experimental algin-incorporated bioactive glass 58S calcium silicate-based (Bio-G) sealer and compared it with commercialised bioceramic-based sealers. A total of 112 lower premolars were instrumented to size 30. Four groups (n = 16) were assigned for the dislodgment resistance test: control, gutta-percha + Bio-G, gutta-percha + BioRoot RCS, and gutta-percha + iRoot SP, with exclusion of the control group in adhesive pattern and dentinal tubule penetration tests. Obturation was done, and teeth were placed in an incubator to allow sealer setting. For the dentinal tubule penetration test, sealers were mixed with 0.1% of rhodamine B dye. Subsequently, teeth were cut into a 1 mm-thick cross section at 5 mm and 10 mm levels from the root apex, respectively. Push-out bond strength, adhesive pattern, and dentinal tubule penetration tests were performed. Bio-G showed the highest mean push-out bond strength (p < 0.05), while iRoot SP showed the greatest sealer penetration (p < 0.05). Bio-G demonstrated more favourable adhesive patterns. No significant association was noted between dislodgment resistance and dentinal tubule penetration (p > 0.05). Full article
(This article belongs to the Special Issue Biomedical Applications of Intelligent Hydrogel)
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12 pages, 4576 KiB  
Article
Enhanced Mechanical Stability and Hydrophobicity of Cellulose Aerogels via Quantitative Doping of Nano-Lignin
by Xiaoyu Wang, Xinyu Yang, Zhen Wu, Xiaoyan Liu, Qian Li, Wenkai Zhu, Yetao Jiang and Lei Hu
Polymers 2023, 15(5), 1316; https://doi.org/10.3390/polym15051316 - 06 Mar 2023
Cited by 4 | Viewed by 1992
Abstract
As a porous biomass sustainable material, cellulose aerogel has attracted significant attention due to its unique properties in various applications. However, its mechanical stability and hydrophobicity are huge obstacles hindering practical applications. In this work, nano-lignin quantitative doping cellulose nanofiber aerogel was successfully [...] Read more.
As a porous biomass sustainable material, cellulose aerogel has attracted significant attention due to its unique properties in various applications. However, its mechanical stability and hydrophobicity are huge obstacles hindering practical applications. In this work, nano-lignin quantitative doping cellulose nanofiber aerogel was successfully fabricated via liquid nitrogen freeze drying combing vacuum oven drying. The impact of various parameters (lignin content, temperature, and matrix concentration) on the property of the as-prepared materials was systematically explored, revealing the optimum conditions. The morphology, mechanical properties, internal structure, and thermal degradation of the as-prepared aerogels were characterized by various methods (compression test, contact angle, SEM, BET, DSC, and TGA). Compared with pure cellulose aerogel, the addition of nano-lignin did not significantly change the pore size and specific surface area of the material but could improve its thermal stability. In particular, the enhanced mechanical stable and hydrophobic properties of cellulose aerogel via the quantitative doping of nano-lignin was confirmed. The mechanical compressive strength of 160–13.5 C/L-aerogel is as high as 0.913 MPa, while the contact angle was nearly reaching 90°. Significantly, this study provides a new strategy for constructing a novel cellulose nanofiber aerogel with mechanical stability and hydrophobicity. Full article
(This article belongs to the Section Polymer Applications)
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16 pages, 2913 KiB  
Article
Branched Amphiphilic Polylactides as a Polymer Matrix Component for Biodegradable Implants
by Vladislav Istratov, Vitaliy Gomzyak, Valerii Vasnev, Oleg V. Baranov, Yaroslav Mezhuev and Inessa Gritskova
Polymers 2023, 15(5), 1315; https://doi.org/10.3390/polym15051315 - 06 Mar 2023
Cited by 3 | Viewed by 1418
Abstract
The combination of biocompatibility, biodegradability, and high mechanical strength has provided a steady growth in interest in the synthesis and application of lactic acid-based polyesters for the creation of implants. On the other hand, the hydrophobicity of polylactide limits the possibilities of its [...] Read more.
The combination of biocompatibility, biodegradability, and high mechanical strength has provided a steady growth in interest in the synthesis and application of lactic acid-based polyesters for the creation of implants. On the other hand, the hydrophobicity of polylactide limits the possibilities of its use in biomedical fields. The ring-opening polymerization of L-lactide, catalyzed by tin (II) 2-ethylhexanoate in the presence of 2,2-bis(hydroxymethyl)propionic acid, and an ester of polyethylene glycol monomethyl ester and 2,2-bis(hydroxymethyl)propionic acid accompanied by the introduction of a pool of hydrophilic groups, that reduce the contact angle, were considered. The structures of the synthesized amphiphilic branched pegylated copolylactides were characterized by 1H NMR spectroscopy and gel permeation chromatography. The resulting amphiphilic copolylactides, with a narrow MWD (1.14–1.22) and molecular weight of 5000–13,000, were used to prepare interpolymer mixtures with PLLA. Already, with the introduction of 10 wt% branched pegylated copolylactides, PLLA-based films had reduced brittleness, hydrophilicity, with a water contact angle of 71.9–88.5°, and increased water absorption. An additional decrease in the water contact angle, of 66.1°, was achieved by filling the mixed polylactide films with 20 wt% hydroxyapatite, which also led to a moderate decrease in strength and ultimate tensile elongation. At the same time, the PLLA modification did not have a significant effect on the melting point and the glass transition temperature; however, the filling with hydroxyapatite increased the thermal stability. Full article
(This article belongs to the Special Issue Scaffolds and Surfaces with Biomedical Applications)
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20 pages, 6449 KiB  
Article
Formation of Porous Structures and Crystalline Phases in Poly(vinylidene fluoride) Membranes Prepared with Nonsolvent-Induced Phase Separation—Roles of Solvent Polarity
by Kuan-Ying Chan, Chia-Ling Li, Da-Ming Wang and Juin-Yih Lai
Polymers 2023, 15(5), 1314; https://doi.org/10.3390/polym15051314 - 06 Mar 2023
Cited by 10 | Viewed by 2387
Abstract
PVDF membranes were prepared with nonsolvent-induced phase separation, using solvents with various dipole moments, including HMPA, NMP, DMAc and TEP. Both the fraction of the polar crystalline phase and the water permeability of the prepared membrane increased monotonously with an increasing solvent dipole [...] Read more.
PVDF membranes were prepared with nonsolvent-induced phase separation, using solvents with various dipole moments, including HMPA, NMP, DMAc and TEP. Both the fraction of the polar crystalline phase and the water permeability of the prepared membrane increased monotonously with an increasing solvent dipole moment. FTIR/ATR analyses were conducted at the surfaces of the cast films during membrane formation to provide information on if the solvents were present as the PVDF crystallized. The results reveal that, with HMPA, NMP or DMAc being used to dissolve PVDF, a solvent with a higher dipole moment resulted in a lower solvent removal rate from the cast film, because the viscosity of the casting solution was higher. The lower solvent removal rate allowed a higher solvent concentration on the surface of the cast film, leading to a more porous surface and longer solvent-governed crystallization. Because of its low polarity, TEP induced non-polar crystals and had a low affinity for water, accounting for the low water permeability and the low fraction of polar crystals with TEP as the solvent. The results provide insight into how the membrane structure on a molecular scale (related to the crystalline phase) and nanoscale (related to water permeability) was related to and influenced by solvent polarity and its removal rate during membrane formation. Full article
(This article belongs to the Section Polymer Membranes and Films)
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16 pages, 2265 KiB  
Review
Mechanisms of Foreign Body Giant Cell Formation in Response to Implantable Biomaterials
by Farshid Eslami-Kaliji, Niloufar Hedayat Nia, Jonathan R. T. Lakey, Alexandra M. Smink and Mohammadreza Mohammadi
Polymers 2023, 15(5), 1313; https://doi.org/10.3390/polym15051313 - 06 Mar 2023
Cited by 4 | Viewed by 6057
Abstract
Long term function of implantable biomaterials are determined by their integration with the host’s body. Immune reactions against these implants could impair the function and integration of the implants. Some biomaterial-based implants lead to macrophage fusion and the formation of multinucleated giant cells, [...] Read more.
Long term function of implantable biomaterials are determined by their integration with the host’s body. Immune reactions against these implants could impair the function and integration of the implants. Some biomaterial-based implants lead to macrophage fusion and the formation of multinucleated giant cells, also known as foreign body giant cells (FBGCs). FBGCs may compromise the biomaterial performance and may lead to implant rejection and adverse events in some cases. Despite their critical role in response to implants, there is a limited understanding of cellular and molecular mechanisms involved in forming FBGCs. Here, we focused on better understanding the steps and mechanisms triggering macrophage fusion and FBGCs formation, specifically in response to biomaterials. These steps included macrophage adhesion to the biomaterial surface, fusion competency, mechanosensing and mechanotransduction-mediated migration, and the final fusion. We also described some of the key biomarkers and biomolecules involved in these steps. Understanding these steps on a molecular level would lead to enhance biomaterials design and improve their function in the context of cell transplantation, tissue engineering, and drug delivery. Full article
(This article belongs to the Special Issue Advances in Polymer Devices for Cell Transplantation)
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18 pages, 6230 KiB  
Article
High-Content Aloe vera Based Hydrogels: Physicochemical and Pharmaceutical Properties
by Mariana Chelu, Monica Popa, Emma Adriana Ozon, Jeanina Pandele Cusu, Mihai Anastasescu, Vasile Adrian Surdu, Jose Calderon Moreno and Adina Magdalena Musuc
Polymers 2023, 15(5), 1312; https://doi.org/10.3390/polym15051312 - 06 Mar 2023
Cited by 10 | Viewed by 4346
Abstract
The present research focuses on the physicochemical and pharmacotechnical properties of new hydrogels obtained using allantoin, xanthan gum, salicylic acid and different concentrations of Aloe vera (5, 10, 20% w/v in solution; 38, 56, 71 wt% in dry gels). The thermal [...] Read more.
The present research focuses on the physicochemical and pharmacotechnical properties of new hydrogels obtained using allantoin, xanthan gum, salicylic acid and different concentrations of Aloe vera (5, 10, 20% w/v in solution; 38, 56, 71 wt% in dry gels). The thermal behavior of Aloe vera composite hydrogels was studied using DSC and TG/DTG analyses. The chemical structure was investigated using different characterization methods (XRD, FTIR and Raman spectroscopies) and the morphology of the hydrogels was studied SEM and AFM microscopy. Pharmacotechnical evaluation on tensile strength and elongation, moisture content, swelling and spreadability was also completed. Physical evaluation confirmed that the appearance of the prepared Aloe vera based hydrogels was homogeneous and the color varied from pale beige to deep opaque beige with increasing Aloe vera concentration. All other evaluation parameters, e.g., pH, viscosity, spreadability and consistency were found to be adequate in all hydrogel formulations. SEM and AFM images show that the structure of the hydrogels condensed into homogeneous polymeric solids with the addition of Aloe vera, in accordance with the decrease in peak intensities observed via XRD analysis. These results suggest interactions between the hydrogel matrix and Aloe vera as observed via FTIR and TG/DTG and DSC analyses. Considering that Aloe vera content higher than 10% (w/v) did not stimulate further interactions, this formulation (FA-10) can be used for further biomedical applications. Full article
(This article belongs to the Special Issue Polymer Composites in Biomedical Applications II)
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16 pages, 3069 KiB  
Article
Black Tea Extracts/Polyvinyl Alcohol Active Nanofibers Electrospun Mats with Sustained Release of Polyphenols for Food Packaging Applications
by Lucía M. Quintero-Borregales, Alicia Vergara-Rubio, Ayelen Santos, Lucía Famá and Silvia Goyanes
Polymers 2023, 15(5), 1311; https://doi.org/10.3390/polym15051311 - 06 Mar 2023
Cited by 3 | Viewed by 2111
Abstract
The efficiency in the capabilities to store and release antioxidants depends on the film morphology and its manufacturing process, as well as on the type and methodology used to obtain the polyphenol extracts. Here, hydroalcoholic extracts of black tea polyphenols (BT) were obtained [...] Read more.
The efficiency in the capabilities to store and release antioxidants depends on the film morphology and its manufacturing process, as well as on the type and methodology used to obtain the polyphenol extracts. Here, hydroalcoholic extracts of black tea polyphenols (BT) were obtained and dropped onto different polyvinyl alcohol (PVA) aqueous solutions (water or BT aqueous extract with and without citric acid, CA) to obtain three unusual PVA electrospun mats containing polyphenol nanoparticles within their nanofibers. It was shown that the mat obtained through the nanoparticles precipitated in BT aqueous extract PVA solution presented the highest total polyphenol content and antioxidant activity, and that the addition of CA as an esterifier or PVA crosslinker interfered with the polyphenols. The release kinetics in different food simulants (hydrophilic, lipophilic and acidic) were fitted using Fick’s diffusion law and Peppas’ and Weibull’s models, showing that polymer chain relaxation is the main mechanism in all food simulants except for the acidic, which presented an abrupt release by Fick’s diffusion mechanism of about 60% before being controlled. This research provides a strategy for the development of promising controlled-release materials for active food packaging, mainly for hydrophilic and acidic food products. Full article
(This article belongs to the Special Issue Electrospun Composite Nanofibers for Functional Applications II)
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12 pages, 1972 KiB  
Article
Cotton Woven Fabrics as Protective Polymer Materials against Solar Radiation in the Range of 210–1200 nm
by Polona Dobnik Dubrovski, Darinka Fakin and Alenka Ojstršek
Polymers 2023, 15(5), 1310; https://doi.org/10.3390/polym15051310 - 06 Mar 2023
Cited by 1 | Viewed by 1425
Abstract
The proposed paper describes the influence of woven fabric constructional parameters (type of weave, relative fabric density) and colouration (obtained by eco-friendly dyeing) on the solar transmittance of cotton woven fabrics in the range of 210–1200 nm. The cotton woven fabrics in their [...] Read more.
The proposed paper describes the influence of woven fabric constructional parameters (type of weave, relative fabric density) and colouration (obtained by eco-friendly dyeing) on the solar transmittance of cotton woven fabrics in the range of 210–1200 nm. The cotton woven fabrics in their raw state were prepared according to Kienbaum’s setting theory, at three levels of relative fabric density and three levels of the weave factor, and then exposed to the dyeing process with natural dyestuffs (beetroot, walnut leaves). After ultraviolet/visible/near-infrared (UV/VIS/IRA) solar transmittance and reflection in the range of 210–1200 nm were recorded, the influence of the fabric construction and colouration were analysed. The guidelines for fabric constructor were proposed. The results show that the walnut-coloured satin samples at the third level of relative fabric density provide the best solar protection in the whole solar spectrum. All the tested eco-friendly dyed fabrics offer good solar protection, while only raw satin fabric at the third level of relative fabric density can be classified as solar protective material with even better protection in IRA region than some coloured samples. Full article
(This article belongs to the Special Issue Recent Advances in Textiles and Fibers)
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15 pages, 339 KiB  
Review
A Review of the Use of Coconut Fiber in Cement Composites
by Flávia Regina Bianchi Martinelli, Francisco Roger Carneiro Ribeiro, Markssuel Teixeira Marvila, Sergio Neves Monteiro, Fabio da Costa Garcia Filho and Afonso Rangel Garcez de Azevedo
Polymers 2023, 15(5), 1309; https://doi.org/10.3390/polym15051309 - 06 Mar 2023
Cited by 20 | Viewed by 16480
Abstract
The use of plant fibers in cementitious composites has been gaining prominence with the need for more sustainable construction materials. It occurs due to the advantages natural fibers provide to these composites, such as the reduction of density, fragmentation, and propagation of cracks [...] Read more.
The use of plant fibers in cementitious composites has been gaining prominence with the need for more sustainable construction materials. It occurs due to the advantages natural fibers provide to these composites, such as the reduction of density, fragmentation, and propagation of cracks in concrete. The consumption of coconut, a fruit grown in tropical countries, generates shells that are improperly disposed of in the environment. The objective of this paper is to provide a comprehensive review of the use of coconut fibers and coconut fiber textile mesh in cement-based materials. For this purpose, discussions were conducted on plant fibers, the production and characteristics of coconut fibers, cementitious composites reinforced with coconut fibers, cementitious composites reinforced with textile mesh as an innovative material to absorb coconut fibers, and treatments of coconut fiber for improved product performance and durability. Finally, future perspectives on this field of study have also been highlighted. Thus, this paper aims to understand the behavior of cementitious matrices reinforced with plant fibers and demonstrate that coconut fiber has a high capacity to be used in cementitious composites instead of synthetic fibers. Full article
12 pages, 3918 KiB  
Article
Preparation and Characterization of Nanocomposite Hydrogels Based on Self-Assembling Collagen and Cellulose Nanocrystals
by Ya Li, Xiaotong Dong, Lihui Yao, Yajuan Wang, Linghui Wang, Zhiqiang Jiang and Dan Qiu
Polymers 2023, 15(5), 1308; https://doi.org/10.3390/polym15051308 - 05 Mar 2023
Cited by 4 | Viewed by 2079
Abstract
Collagen (Col) hydrogels are an important biomaterial with many applications in the biomedical sector. However, deficiencies, including insufficient mechanical properties and a rapid rate of biodegradation, hamper their application. In this work, nanocomposite hydrogels were prepared by combining a cellulose nanocrystal (CNC) with [...] Read more.
Collagen (Col) hydrogels are an important biomaterial with many applications in the biomedical sector. However, deficiencies, including insufficient mechanical properties and a rapid rate of biodegradation, hamper their application. In this work, nanocomposite hydrogels were prepared by combining a cellulose nanocrystal (CNC) with Col without any chemical modification. The high-pressure, homogenized CNC matrix acts as nuclei in the collagen’s self-aggregation process. The obtained CNC/Col hydrogels were characterized in terms of their morphology, mechanical and thermal properties and structure by SEM, rotational rheometer, DSC and FTIR, respectively. Ultraviolet-visible spectroscopy was used to characterize the self-assembling phase behavior of the CNC/Col hydrogels. The results showed an accelerated assembling rate with the increasing loading of CNC. The triple-helix structure of the collagen was preserved with a dosage of CNC of up to 15 wt%. The CNC/Col hydrogels demonstrated an improvement in both the storage modulus and thermal stability which is attributed to the interaction between the CNC and collagen by the hydrogen bonds. Full article
(This article belongs to the Special Issue Polymeric Composite Nanomaterials in Medicine)
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17 pages, 4627 KiB  
Review
Recent Advances in Degradation of Polymer Plastics by Insects Inhabiting Microorganisms
by Rongrong An, Chengguo Liu, Jun Wang and Puyou Jia
Polymers 2023, 15(5), 1307; https://doi.org/10.3390/polym15051307 - 05 Mar 2023
Cited by 7 | Viewed by 5017
Abstract
Plastic pollution endangers all natural ecosystems and living creatures on earth. Excessive reliance on plastic products and excessive production of plastic packaging are extremely dangerous for humans because plastic waste has polluted almost the entire world, whether it is in the sea or [...] Read more.
Plastic pollution endangers all natural ecosystems and living creatures on earth. Excessive reliance on plastic products and excessive production of plastic packaging are extremely dangerous for humans because plastic waste has polluted almost the entire world, whether it is in the sea or on the land. This review introduces the examination of pollution brought by non-degradable plastics, the classification and application of degradable materials, and the current situation and strategy to address plastic pollution and plastic degradation by insects, which mainly include Galleria mellonella, Zophobas atratus, Tenebrio molitor, and other insects. The efficiency of plastic degradation by insects, biodegradation mechanism of plastic waste, and the structure and composition of degradable products are reviewed. The development direction of degradable plastics in the future and plastic degradation by insects are prospected. This review provides effective ways to solve plastic pollution. Full article
(This article belongs to the Special Issue Natural-Based Biodegradable Polymeric Materials)
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14 pages, 3204 KiB  
Communication
Facile Synthesis of Light-Switchable Polymers with Diazocine Units in the Main Chain
by Shuo Li, Katrin Bamberg, Yuzhou Lu, Frank D. Sönnichsen and Anne Staubitz
Polymers 2023, 15(5), 1306; https://doi.org/10.3390/polym15051306 - 05 Mar 2023
Cited by 3 | Viewed by 1728
Abstract
Unlike azobenzene, the photoisomerization behavior of its ethylene-bridged derivative, diazocine, has hardly been explored in synthetic polymers. In this communication, linear photoresponsive poly(thioether)s containing diazocine moieties in the polymer backbone with different spacer lengths are reported. They were synthesized in thiol-ene polyadditions between [...] Read more.
Unlike azobenzene, the photoisomerization behavior of its ethylene-bridged derivative, diazocine, has hardly been explored in synthetic polymers. In this communication, linear photoresponsive poly(thioether)s containing diazocine moieties in the polymer backbone with different spacer lengths are reported. They were synthesized in thiol-ene polyadditions between a diazocine diacrylate and 1,6-hexanedithiol. The diazocine units could be reversibly photoswitched between the (Z)- and (E)-configurations with light at 405 nm and 525 nm, respectively. Based on the chemical structure of the diazocine diacrylates, the resulting polymer chains differed in their thermal relaxation kinetics and molecular weights (7.4 vs. 43 kDa) but maintained a clearly visible photoswitchability in the solid state. Gel permeation chromatography (GPC) measurements indicated a hydrodynamic size expansion of the individual polymer coils as a result of the ZE pincer-like diazocine switching motion on a molecular scale. Our work establishes diazocine as an elongating actuator that can be used in macromolecular systems and smart materials. Full article
(This article belongs to the Special Issue Stimuli-Responsive Polymers)
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12 pages, 5302 KiB  
Article
All-Organic PTFE Coated PVDF Composite Film Exhibiting Low Conduction Loss and High Breakdown Strength for Energy Storage Applications
by Xiang-Shuo Meng, Yujiu Zhou, Jianfeng Li, Hu Ye, Fujia Chen, Yuetao Zhao, Qifeng Pan and Jianhua Xu
Polymers 2023, 15(5), 1305; https://doi.org/10.3390/polym15051305 - 05 Mar 2023
Cited by 2 | Viewed by 1419
Abstract
Plastic film capacitors are widely used in pulse and energy storage applications because of their high breakdown strength, high power density, long lifetime, and excellent self-healing properties. Nowadays, the energy storage density of commercial biaxially oriented polypropylene (BOPP) is limited by its low [...] Read more.
Plastic film capacitors are widely used in pulse and energy storage applications because of their high breakdown strength, high power density, long lifetime, and excellent self-healing properties. Nowadays, the energy storage density of commercial biaxially oriented polypropylene (BOPP) is limited by its low dielectric constant (~2.2). Poly(vinylidene fluoride) (PVDF) exhibits a relatively high dielectric constant and breakdown strength, making it a candidate material for electrostatic capacitors. However, PVDF presents significant losses, generating a lot of waste heat. In this paper, under the guidance of the leakage mechanism, a high-insulation polytetrafluoroethylene (PTFE) coating is sprayed on the surface of a PVDF film. The potential barrier at the electrode–dielectric interface is raised by simply spraying PTFE and reducing the leakage current, and then the energy storage density is increased. After introducing the PTFE insulation coating, the high-field leakage current in the PVDF film shows an order of magnitude reduction. Moreover, the composite film presents a 30.8% improvement in breakdown strength, and a 70% enhancement in energy storage density is simultaneously achieved. The all-organic structure design provides a new idea for the application of PVDF in electrostatic capacitors. Full article
(This article belongs to the Section Polymer Applications)
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14 pages, 7042 KiB  
Article
Facile Synthesis of Reduced-Graphene-Oxide-Modified Ammonium Polyphosphate to Enhance the Flame Retardancy, Smoke Release Suppression, and Mechanical Properties of Epoxy Resin
by Feiyue Wang, Jiahao Liao, Miaotian Long, Long Yan and Mengtao Cai
Polymers 2023, 15(5), 1304; https://doi.org/10.3390/polym15051304 - 05 Mar 2023
Cited by 5 | Viewed by 1483
Abstract
A unique hybridized intumescent flame retardant named reduced-graphene-oxide-modified ammonium polyphosphate (RGO-APP) was successfully synthesized via the simple hydrothermal method and reduced process. Then, the obtained RGO-APP was applied in epoxy resin (EP) for flame retardancy reinforcement. The addition of RGO-APP results in a [...] Read more.
A unique hybridized intumescent flame retardant named reduced-graphene-oxide-modified ammonium polyphosphate (RGO-APP) was successfully synthesized via the simple hydrothermal method and reduced process. Then, the obtained RGO-APP was applied in epoxy resin (EP) for flame retardancy reinforcement. The addition of RGO-APP results in a significant reduction in heat release and smoke production from the EP, which is attributed to EP/RGO-APP producing a more compact and intumescent char against the heat transfer and combustible decomposition, thus enhancing the fire safety of EP, as confirmed by char residue analysis. Especially, the EP containing 15 wt% RGO-APP acquires a limiting oxygen index (LOI) value of 35.8% and shows a 83.6% reduction in peak heat release rate and a 74.3% reduction in peak smoke production rate compared with those of pure EP. The tensile test exhibits that the presence of RGO-APP favors the enhancement in tensile strength and elastic modulus of EP due to the good compatibility between flame retardant and epoxy matrix, as supported by differential scanning calorimetry (DSC) and scanning electron microscope (SEM) analyses. This work provides a new strategy for the modification of APP, thus facilitating a promising application in polymeric materials. Full article
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34 pages, 15626 KiB  
Article
A Study on mPPO Development and Injection Molding Process for Lightweight Stack Enclosure of FCEV
by Soo-Lim Lee, Jong-Hwal Kim and Seon-Bong Lee
Polymers 2023, 15(5), 1303; https://doi.org/10.3390/polym15051303 - 04 Mar 2023
Cited by 1 | Viewed by 1142
Abstract
The automobile industry is focused on eco-friendly vehicles with the goal of carbon neutrality (Netzero), and vehicle weight reduction is essential to achieve high fuel efficiency for driving performance and distance compared to internal combustion engines. This is important for the light-weight stack [...] Read more.
The automobile industry is focused on eco-friendly vehicles with the goal of carbon neutrality (Netzero), and vehicle weight reduction is essential to achieve high fuel efficiency for driving performance and distance compared to internal combustion engines. This is important for the light-weight stack enclosure of FCEV. Moreover, mPPO needs to be developed with injection molding for the replacement of existing material (aluminum). For this purpose, this study develops mPPO and presents it through physical property tests, predicts the injection molding process flow system for stack enclosure production, proposes injection molding process conditions to secure productivity, and verifies conditions through mechanical stiffness analysis. As a result of the analysis, the runner system with pin-point gate and tab gate’s sizes are proposed. In addition, injection molding process conditions were proposed with the results of cycle time 107.627 s and reduced weld lines. As a result of the strength analysis, it can withstand the load 5933 kg. Therefore, it is possible to reduce weight and material costs using the mPPO existing manufacturing process with existing aluminum, and it is expected that there would be effects, such as reducing the production cost by securing productivity through reducing cycle time. Full article
(This article belongs to the Section Polymer Processing and Engineering)
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18 pages, 5127 KiB  
Article
Bio-Based Adhesives Formulated from Tannic Acid, Chitosan, and Shellac for Packaging Materials
by Urška Vrabič-Brodnjak
Polymers 2023, 15(5), 1302; https://doi.org/10.3390/polym15051302 - 04 Mar 2023
Cited by 4 | Viewed by 2408
Abstract
The aim of this study was to develop bio-based adhesives that can be used for various packaging papers. In addition to commercial paper samples, papers produced from harmful plant species in Europe, such as Japanese Knotweed and Canadian Goldenrod, were used. In this [...] Read more.
The aim of this study was to develop bio-based adhesives that can be used for various packaging papers. In addition to commercial paper samples, papers produced from harmful plant species in Europe, such as Japanese Knotweed and Canadian Goldenrod, were used. In this research, methods were developed to produce bio-based adhesive solutions in combinations of tannic acid, chitosan, and shellac. The results showed that the viscosity and adhesive strength of the adhesives were best in solutions with added tannic acid and shellac. The tensile strength with adhesives of tannic acid and chitosan was 30% better than with commercial adhesives and 23% for combinations of shellac and chitosan. For paper from Japanese Knotweed and Canadian Goldenrod, the most durable adhesive was pure shellac. Because the surface morphology of the invasive plant papers was more open and had numerous pores compared to the commercial papers, the adhesives penetrated the paper structure and filled the voids. There was less adhesive on the surface and the commercial papers achieved better adhesive properties. As expected, the bio-based adhesives also showed an increase in peel strength and exhibited favorable thermal stability. In summary, these physical properties support the use of bio-based adhesives use in different packaging applications. Full article
(This article belongs to the Special Issue Biomass-Derived Polymers II)
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15 pages, 4635 KiB  
Article
Investigation of Performance of Anion Exchange Membrane (AEM) Electrolysis with Different Operating Conditions
by Adam Mohd Izhan Noor Azam, Thuushren Ragunathan, Nurul Noramelya Zulkefli, Mohd Shahbudin Masdar, Edy Herianto Majlan, Rozan Mohamad Yunus, Noor Shahirah Shamsul, Teuku Husaini and Siti Nur Amira Shaffee
Polymers 2023, 15(5), 1301; https://doi.org/10.3390/polym15051301 - 04 Mar 2023
Cited by 7 | Viewed by 2887
Abstract
In this work, the performance of anion exchange membrane (AEM) electrolysis is evaluated. A parametric study is conducted, focusing on the effects of various operating parameters on the AEM efficiency. The following parameters—potassium hydroxide (KOH electrolyte concentration (0.5–2.0 M), electrolyte flow rate (1–9 [...] Read more.
In this work, the performance of anion exchange membrane (AEM) electrolysis is evaluated. A parametric study is conducted, focusing on the effects of various operating parameters on the AEM efficiency. The following parameters—potassium hydroxide (KOH electrolyte concentration (0.5–2.0 M), electrolyte flow rate (1–9 mL/min), and operating temperature (30–60 °C)—were varied to understand their relationship to AEM performance. The performance of the electrolysis unit is measured by its hydrogen production and energy efficiency using the AEM electrolysis unit. Based on the findings, the operating parameters greatly influence the performance of AEM electrolysis. The highest hydrogen production was achieved with the operational parameters of 2.0 M electrolyte concentration, 60 °C operating temperature, and 9 mL/min electrolyte flow at 2.38 V applied voltage. Hydrogen production of 61.13 mL/min was achieved with an energy consumption of 48.25 kW·h/kg and an energy efficiency of 69.64%. Full article
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16 pages, 3903 KiB  
Article
Improvement of Heat Resistance of Fluorosilicone Rubber Employing Vinyl-Functionalized POSS as a Chemical Crosslinking Agent
by Jae Il So, Chung Soo Lee, Byeong Seok Kim, Hyeon Woo Jeong, Jin Sung Seo, Sung Hyeon Baeck, Sang Eun Shim and Yingjie Qian
Polymers 2023, 15(5), 1300; https://doi.org/10.3390/polym15051300 - 04 Mar 2023
Cited by 1 | Viewed by 1803
Abstract
Fluorosilicone rubber (F-LSR) is a promising material that can be applied in various cutting-edge industries. However, the slightly lower thermal resistance of F-LSR compared with that of conventional PDMS is difficult to overcome by applying nonreactive conventional fillers that readily agglomerate owing to [...] Read more.
Fluorosilicone rubber (F-LSR) is a promising material that can be applied in various cutting-edge industries. However, the slightly lower thermal resistance of F-LSR compared with that of conventional PDMS is difficult to overcome by applying nonreactive conventional fillers that readily agglomerate owing to their incompatible structure. Polyhedral oligomeric silsesquioxane with vinyl groups (POSS-V) is a suitable material that may satisfy this requirement. Herein, F-LSR-POSS was prepared using POSS-V as a chemical crosslinking agent chemically bonded with F-LSR through hydrosilylation. All F-LSR-POSSs were successfully prepared and most of the POSS-Vs were uniformly dispersed in the F-LSR-POSSs, as confirmed by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H-NMR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) measurements. The mechanical strength and crosslinking density of the F-LSR-POSSs were determined using a universal testing machine (UTM) and dynamic mechanical analysis (DMA), respectively. Finally, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements confirmed that the low-temperature thermal properties were maintained, and the heat resistance was significantly improved compared with conventional F-LSR. Eventually, the poor heat resistance of the F-LSR was overcome with three-dimensional high-density crosslinking by introducing POSS-V as a chemical crosslinking agent, thereby expanding the potential fluorosilicone applications. Full article
(This article belongs to the Collection Silicon-Containing Polymeric Materials)
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22 pages, 6126 KiB  
Article
On the Vibration-Damping Properties of the Prestressed Polyurethane Granular Material
by Aleš Gosar, Igor Emri, Jernej Klemenc, Marko Nagode and Simon Oman
Polymers 2023, 15(5), 1299; https://doi.org/10.3390/polym15051299 - 04 Mar 2023
Cited by 2 | Viewed by 2085
Abstract
Granular materials promise opportunities for the development of high-performance, lightweight vibration-damping elements that provide a high level of safety and comfort. Presented here is an investigation of the vibration-damping properties of prestressed granular material. The material studied is thermoplastic polyurethane (TPU) in Shore [...] Read more.
Granular materials promise opportunities for the development of high-performance, lightweight vibration-damping elements that provide a high level of safety and comfort. Presented here is an investigation of the vibration-damping properties of prestressed granular material. The material studied is thermoplastic polyurethane (TPU) in Shore 90A and 75A hardness grades. A method for preparing and testing the vibration-damping properties of tubular specimens filled with TPU granules was developed. A new combined energy parameter was introduced to evaluate the damping performance and weight-to-stiffness ratio. Experimental results show that the material in granular form provides up to 400% better vibration-damping performance as compared to the bulk material. Such improvement is possible by combining both the effect of the pressure–frequency superposition principle at the molecular scale and the effect of the physical interactions between the granules (force-chain network) at the macro scale. The two effects complement each other, with the first effect predominating at high prestress and the second at low prestress. Conditions can be further improved by varying the material of the granules and applying a lubricant that facilitates the granules to reorganize and reconfigure the force-chain network (flowability). Full article
(This article belongs to the Section Polymer Applications)
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17 pages, 2256 KiB  
Article
Fabrication of Novel Omeprazole-Based Chitosan Coated Nanoemulgel Formulation for Potential Anti-Microbia; In Vitro and Ex Vivo Characterizations
by Irshad Ullah, Aiyeshah Alhodaib, Iffat Naz, Waqar Ahmad, Hidayat Ullah, Adnan Amin and Asif Nawaz
Polymers 2023, 15(5), 1298; https://doi.org/10.3390/polym15051298 - 04 Mar 2023
Cited by 2 | Viewed by 1628
Abstract
Infectious diseases remain inevitable factors for high mortality and morbidity rate in the modern world to date. Repurposing is a novel approach to drug development has become an intriguing research topic in the literature. Omeprazole is one of the top ten proton pump [...] Read more.
Infectious diseases remain inevitable factors for high mortality and morbidity rate in the modern world to date. Repurposing is a novel approach to drug development has become an intriguing research topic in the literature. Omeprazole is one of the top ten proton pump inhibitors prescribed in the USA. The literature suggests that no reports based on omeprazole anti-microbial actions have been discovered to date. This study entails the potential of omeprazole to treat skin and soft tissue infections based on the literature’s evident anti-microbial effects. To get a skin-friendly formulation, a chitosan-coated omeprazole-loaded nanoemulgel formulation was fabricated using olive oil, carbopol 940, Tween 80, Span 80, and triethanolamine by high-speed homogenization technique. The optimized formulation was physicochemically characterized for zeta potential, size distribution, pH, drug content, entrapment efficiency, viscosity, spreadability, extrudability, in-vitro drug release, ex-vivo permeation analysis, and minimum inhibitory concentration determination. The FTIR analysis indicated that there was no incompatibility between the drug and formulation excipients. The optimized formulation exhibited particle size, PDI, zeta potential, drug content, and entrapment efficiency of 369.7 ± 8.77 nm, 0.316, −15.3 ± 6.7 mV, 90.92 ± 1.37% and 78.23 ± 3.76%, respectively. In-vitro release and ex-vivo permeation data of optimized formulation showed 82.16% and 72.21 ± 1.71 μg/cm2, respectively. The results of minimum inhibitory concentration (1.25 mg/mL) against selected bacterial strains were satisfactory, suggesting a successful treatment approach for the topical application of omeprazole to treat microbial infections. Furthermore, chitosan coating synergistically increases the antibacterial activity of the drug. Full article
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