Polymers

23 pages, 2409 KiB

Open AccessArticle

Physico-Mechanical Properties of 3D-Printed Filament Materials for Mouthguard Manufacturing

by Maciej Trzaskowski, Gen Tanabe, Hiroshi Churei, Toshiaki Ueno, Michał Ziętala, Bartłomiej Wysocki, Judyta Sienkiewicz, Agata Szczesio-Włodarczyk, Jerzy Sokołowski, Ewa Czochrowska, Małgorzata Zadurska, Elżbieta Mierzwińska-Nastalska, Jolanta Kostrzewa-Janicka and Katarzyna Mańka-Malara

Polymers 2025, 17(16), 2190; https://doi.org/10.3390/polym17162190 (registering DOI) - 10 Aug 2025

Abstract

Mouthguards are recommended for all sports that may cause injuries to the head and oral cavity. Custom mouthguards, made conventionally in the thermoforming process from ethylene vinyl acetate (EVA), face challenges with thinning at the incisor area during the process. In contrast, additive [...] Read more.

Mouthguards are recommended for all sports that may cause injuries to the head and oral cavity. Custom mouthguards, made conventionally in the thermoforming process from ethylene vinyl acetate (EVA), face challenges with thinning at the incisor area during the process. In contrast, additive manufacturing (AM) processes enable the precise reproduction of the dimensions specified in a computer-aided design (CAD) model. The potential use of filament extrusion materials in the fabrication of custom mouthguards has not yet been explored in comparative studies. Our research aimed to compare five commercially available filaments for the material extrusion (MEX) also known as fused deposition modelling (FDM) of custom mouthguards using a desktop 3D printer. Samples made using Copper 3D PLActive, Spectrum Medical ABS, Braskem Bio EVA, DSM Arnitel ID 2045, and NinjaFlex were compared to EVA Erkoflex, which served as a control sample. The samples underwent tests for ultimate tensile strength (UTS), split Hopkinson pressure bar (SHPB) performance, drop-ball impact, abrasion resistance, absorption, and solubility. The results showed that Copper 3D PLActive and Spectrum Medical ABS had the highest tensile strength. DSM Arnitel ID 2045 had the highest dynamic property performance, measured with the SHPB and drop-ball tests. On the other hand, NinjaFlex exhibited the lowest abrasion resistance and the highest absorption and solubility. DSM Arnitel ID 2045’s absorption and solubility levels were comparable to those of EVA, but had significantly lower abrasion resistance. Ultimately, DSM Arnitel ID 2045 is recommended as the best filament for 3D-printing mouthguards. The properties of this biocompatible material ensure high-impact energy absorption while maintaining low fluid sorption and solubility, supporting its safe intra-oral application for mouthguard fabrication. However, its low abrasion resistance indicated that mouthguards made from this material may need to be replaced more frequently. Full article

(This article belongs to the Special Issue Polymers Composites for Dental Applications, 2nd Edition)

26 pages, 6937 KiB

Open AccessArticle

Effect of pH, Temperature, Molecular Weight and Salt Concentration on the Structure and Hydration of Short Poly(N,N-dimethylaminoethyl methacrylate) Chains in Dilute Aqueous Solutions: A Combined Experimental and Molecular Dynamics Study

by Dimitris G. Mintis, Marco Dompé, Panagiotis D. Kolokathis, Jasper van der Gucht, Antreas Afantitis and Vlasis G. Mavrantzas

Polymers 2025, 17(16), 2189; https://doi.org/10.3390/polym17162189 (registering DOI) - 10 Aug 2025

Abstract

We study the microstructural properties and state of hydration of aqueous low-molecular-weight poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) solutions and their dependence on polymer concentration and pH by means of detailed atomistic Molecular Dynamics (MD) simulations and experiments. For infinitely dilute solutions [...] Read more.

We study the microstructural properties and state of hydration of aqueous low-molecular-weight poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) solutions and their dependence on polymer concentration and pH by means of detailed atomistic Molecular Dynamics (MD) simulations and experiments. For infinitely dilute solutions with a degree of polymerization of N = 30 at basic pH conditions, no temperature dependence is observed on the overall shape and state of hydration of the polyelectrolyte. This is supported by the experimental component of our work according to which the hydrodynamic radius, R_h, does not change dramatically with temperature. Small, but not drastic, changes are observed for solutions with longer PDMAEMA chains (N = 50, 70, and 110). Although the MD simulations demonstrate that temperature and salt do affect the strength of hydrophobic interactions between PDMAEMA and water, apparently these effects are not strong enough to cause drastic changes to the overall shape of the polymer. MD simulations also reveal that Na⁺ salt ions strongly interact with the oxygen atoms located at the side chain of the polyelectrolyte. While no significant changes in the global shape or state of hydration of the PDMAEMA chain are found, a strong dependence is revealed for the aggregation behavior of the polymer on temperature and salt in slightly more concentrated solutions. A structural transition from a collapsed coil to a stretched conformation is also observed as we move from basic to acidic pH conditions, which is strongly correlated with the degree of chain rigidity as a function of pH. Full article

(This article belongs to the Special Issue Designing Polymers for Emerging Applications)

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20 pages, 2271 KiB

Open AccessArticle

Development of Gelatin/Polyvinyl Alcohol Films Incorporated with Blueberry Extracts for Freshness Detection of Shrimp

by Bárbara Teixeira Gomes, Meirielly Jesus, Joana Santos, Clara Suprani Marques, Noé Mitterhofer Eiterer Ponce de Leon da Costa, Fernando Mata, Paulo Cesar Stringheta, Taila Veloso de Oliveira and Nilda de Fatima Ferreira Soares

Polymers 2025, 17(16), 2188; https://doi.org/10.3390/polym17162188 (registering DOI) - 10 Aug 2025

Abstract

The objective of this study was to evaluate the physical, chemical, mechanical, thermal, and topological properties of polyvinyl alcohol (PVA) and gelatin (GL) films after incorporating three different fractions of blueberry extract: crude extract (EB, without purification), phenolic portion (EF), and concentrated anthocyanins [...] Read more.

The objective of this study was to evaluate the physical, chemical, mechanical, thermal, and topological properties of polyvinyl alcohol (PVA) and gelatin (GL) films after incorporating three different fractions of blueberry extract: crude extract (EB, without purification), phenolic portion (EF), and concentrated anthocyanins (EA). Additionally, the study aimed to analyze the efficiency of these colorimetric indicator films in monitoring the freshness quality of shrimp. The experiment followed a completely randomized design with one factor—different types of films—studied at six levels: film incorporated with crude blueberry extract (FB), film incorporated with phenolic extract (FF), and film incorporated with anthocyanin extract (FA), in addition to the control films: the plasticized blend containing glycerol, PVA, and GL (FC), the pristine gelatin film (FG), and the pristine PVA film (FPVA). To evaluate the colorimetric sensitivity of the indicators applied to shrimp, storage time was studied at two levels: T0 (before storage—on the day of collection) and T7 (after 7 days of storage at 6.5 ± 1 °C) for the FB and FA films. Regarding thermal properties, the degradation profile occurred in three stages, with the FC film being the most thermally stable. In terms of mechanical behavior, the isolated anthocyanin content increased the elasticity of FA, while the crude extract and other phenolic compounds contributed to the stiffness of FB (Young’s modulus, YM = 22.52) and FF (YM = 37.33). Structurally, the FC film exhibited a smooth and well-blended polymeric surface, whereas FF, FB, and FA displayed heterogeneous and discontinuous phases. The incorporation of blueberry extracts reduced water absorption, leading to decreased swelling and solubility. FF showed the lowest solubility (S = 16.14%), likely due to hydrogen bonding between phenolic compounds and the polymer matrix. Notably, FB demonstrated superior physical, chemical, and mechanical performance, as well as the highest thermal stability among the extract-containing films. It also showed a visible color change (from purple to green/brown) after 7 days of shrimp storage, corresponding with spoilage and pH values unsuitable for consumption. Both FA and FB effectively monitored shrimp freshness, offering a sustainable approach to quality assurance and food waste reduction. Among them, FB was the most practical for visual detection. Overall, these films demonstrated strong potential as pH-sensitive indicators for evaluating the freshness of shrimp. Full article

(This article belongs to the Section Polymer Membranes and Films)

28 pages, 2183 KiB

Open AccessReview

Production Technologies and Application of Polymer Composites in Engineering: A Review

by Milan Bukvić, Saša Milojević, Sandra Gajević, Momčilo Đorđević and Blaža Stojanović

Polymers 2025, 17(16), 2187; https://doi.org/10.3390/polym17162187 (registering DOI) - 9 Aug 2025

Abstract

Composite materials have been increasingly used in various branches of industry, transport, construction, and medicine—as well as in other sectors of the economy and science—in recent decades. A significant advancement in the improvement of composite material characteristics has been achieved through the use [...] Read more.

Composite materials have been increasingly used in various branches of industry, transport, construction, and medicine—as well as in other sectors of the economy and science—in recent decades. A significant advancement in the improvement of composite material characteristics has been achieved through the use of nanoparticles, which substantially enhance the properties of the base material, whether it is the matrix or the reinforcing phase in hybrid composites. The broad application of polymers and polymer composites in many areas of engineering has had a significant impact on reducing friction and wear, improving the thermal characteristics of individual components and entire technical systems, enhancing electrical conductivity, reducing the specific weight of components, lowering noise and vibration levels, and ultimately decreasing fuel consumption, production costs, and the costs of operation and maintenance of technical systems. This paper explores the potential applications of polymer composites in various assemblies and components of conventional vehicles, as well as in hybrid and electric vehicles. Furthermore, their use in medicine and the defense industry is examined—fields in which some authors believe composites were first pioneered. Finally, aviation represents an indispensable domain for the application of such materials, presenting unique exploitation boundary conditions, including dynamic environmental changes such as variations in temperature, pressure, velocity, and direction, as well as the need for high levels of protection. Future research can be unequivocally focused on the structural and technological advancement of polymer composites, specifically through optimization aimed at reducing waste and lowering production costs. Full article

(This article belongs to the Special Issue Polymeric Composites: Manufacturing, Processing and Applications)

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28 pages, 5694 KiB

Open AccessArticle

Polymers in Sustainable Construction Composites: Rheology, Mechanical Performance, and Durability

by Yahya Kaya, Veysel Kobya, Murteda Ünverdi, Naz Mardani and Ali Mardani

Polymers 2025, 17(16), 2186; https://doi.org/10.3390/polym17162186 (registering DOI) - 9 Aug 2025

Abstract

Today, various strategies are being adopted to produce more environmentally friendly cementitious systems. A commonly adopted strategy is the enhancement of energy efficiency in the clinker grinding process through the use of grinding aids (GAs). Another approach is to reduce cement consumption by [...] Read more.

Today, various strategies are being adopted to produce more environmentally friendly cementitious systems. A commonly adopted strategy is the enhancement of energy efficiency in the clinker grinding process through the use of grinding aids (GAs). Another approach is to reduce cement consumption by partially replacing cement with mineral additives such as fly ash. The literature has highlighted that the use of GAs during clinker grinding can narrow the particle size distribution, thereby promoting higher rates of mineral additive replacement. Nevertheless, the literature still lacks comprehensive insight into how the combined application of commonly used GAs influences the substitution levels of mineral additives. In this regard, this study thoroughly examined the influence of varying proportions and dosages of Triethanolamine (TEA) and Triisopropanolamine (TIPA)—two commonly employed grinding aids—on the hydration kinetics, compressive strength development, and life cycle performance of fly ash (FA)-blended cementitious systems. The mixtures prepared with the cements produced were analyzed through XRD, TGA, and SEM techniques, and the compressive strength results were evaluated using the Taguchi method. The results demonstrated that, irrespective of the type of additive used, the use of GAs enhanced pozzolanic activity and compressive strength. In particular, the GA combination containing 75% TIPA and 25% TEA proved the most superior results in terms of hydration kinetics, mechanical strength, and environmental performance. It was demonstrated that the combined use of TEA and TIPA in specific proportions creates a synergistic effect, enabling the development of more efficient binder systems. Full article

(This article belongs to the Special Issue Application of Polymers in Cementitious Materials)

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25 pages, 6160 KiB

Open AccessArticle

Electrospun Polyvinyl Alcohol/Sodium Alginate Nanocomposite Dressings Loaded with ZnO and Bioglass: Characterization, Antibacterial Activity, and Cytocompatibility

by J. Andrés Ortiz, Francesca Antonella Sepúlveda, Siomara Flores, Marcela Saavedra, Suhelen Sáez-Silva, Thomas Jiménez, Paola Murgas, Scarlett Troncoso, Camila Sanhueza, María T. Ulloa, Lorena Porte Torre, Manuel Ahumada, Teresa Corrales, Humberto Palza and Paula A. Zapata

Polymers 2025, 17(16), 2185; https://doi.org/10.3390/polym17162185 (registering DOI) - 9 Aug 2025

Abstract

Chronic wounds pose a great challenge due to their slow healing and susceptibility to infections, hence the need for innovative alternatives to conventional antibiotics, as increasing bacterial resistance limits the efficacy of current treatments. This paper addresses the development of novel electrospun membranes [...] Read more.

Chronic wounds pose a great challenge due to their slow healing and susceptibility to infections, hence the need for innovative alternatives to conventional antibiotics, as increasing bacterial resistance limits the efficacy of current treatments. This paper addresses the development of novel electrospun membranes based on polyvinyl alcohol (PVA) and sodium alginate, incorporating therapeutic ZnO and bioglass (54SiO₂:40CaO:6P₂O₅) nanoparticles. While nanocomposites presented smaller fiber diameters than pure polymers, ternary nanocomposites displayed higher values, e.g., in porous areas, values were in the ca. 80 - 240 nm range and 0.06 - 0.60 mm², respectively. The Young's modulus of the PVA/SA membrane, initially 15.9 ± 2.0 MPa, decreased by 65% with 10 wt.% ZnO NPs, whereas 10 wt.% BG NPs increased it by 100%. The membranes demonstrated efficacy against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) isolated from a human wound secretion, as well as two ATCC strains: Staphylococcus aureus and Staphylococcus epidermidis. A cell viability assay conducted with HaCaT cells demonstrated nearly complete survival following 72 h of membrane exposure. Their combined Gram-positive antibacterial activity and cytocompatibility support their potential application as biofunctional dressings for the management of chronic and hospital-acquired topical infections, while also contributing to the global effort to combat antibiotic resistance. Full article

(This article belongs to the Special Issue Electrospun Nanofibers: Current Advances and Future Perspective)

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20 pages, 3627 KiB

Open AccessArticle

Crown Ether-Functionalized Polyethersulfone Membranes with Potential Applications in Hemodialysis

by Madalina Oprea, Andreea Madalina Pandele, Catalin Ionel Enachescu, Iulian Vasile Antoniac, Stefan Ioan Voicu and Anca Maria Fratila

Polymers 2025, 17(16), 2184; https://doi.org/10.3390/polym17162184 (registering DOI) - 9 Aug 2025

Abstract

Polyethersulfone (PES) is one of the most used synthetic polymers for the production of hemodialysis membranes, due to its appropriate features, such as biocompatibility, high permeability for low-molecular-weight proteins, high endotoxin retention ability, and resistance to sterilization processes. However, there is room for [...] Read more.

Polyethersulfone (PES) is one of the most used synthetic polymers for the production of hemodialysis membranes, due to its appropriate features, such as biocompatibility, high permeability for low-molecular-weight proteins, high endotoxin retention ability, and resistance to sterilization processes. However, there is room for improvement regarding their anticoagulant properties when coming into contact with blood. In the present study, commercial PES membranes were plasma-treated and then chemically modified with crown ether, an organic compound that could interfere with the coagulation cascade by complexating Ca²⁺ in the blood. The physico-chemical and morphological characteristics of the membranes were determined by FT-IR, XPS, TGA, SEM, and CT analyses, while their efficiency in retaining calcium ions was evaluated via ICP-MS. The results revealed that plasma treatment with a mixture of argon and ammonia was the most effective in generating nitrogen-containing surface functional groups and that these moieties can be successfully used for the covalent functionalization of the membranes. Also, the Ca²⁺ retention ability of the PES membranes was improved by up to 30% after chemical modification with 4′-aminobenzo-15-crown-5 ether. Full article

(This article belongs to the Section Polymer Applications)

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14 pages, 3367 KiB

Open AccessArticle

Realization of a 27.5 °C Atmospheric Microwave Plasma Jet at 8 W for Surface Modification of Thermosensitive Polymers

by Dongxue Han, Wencong Zhang, Yong Yang, Yuantao Huang, Jiangqi Yu, Li Wu, Wenyan Tian and Huacheng Zhu

Polymers 2025, 17(16), 2183; https://doi.org/10.3390/polym17162183 (registering DOI) - 9 Aug 2025

Abstract

Atmospheric pressure plasma jets (APPJs) enable efficient solvent-free surface modification to enhance the wettability, adhesion, and biocompatibility of polymers. However, conventional APPJs often generate high temperatures and energetic particles, which lead to melting, surface degradation, and molecular damage of thermosensitive polymers, thus limiting [...] Read more.

Atmospheric pressure plasma jets (APPJs) enable efficient solvent-free surface modification to enhance the wettability, adhesion, and biocompatibility of polymers. However, conventional APPJs often generate high temperatures and energetic particles, which lead to melting, surface degradation, and molecular damage of thermosensitive polymers, thus limiting their scope of application. This study demonstrates an optimized atmospheric pressure microwave plasma jet (MPJ) operating at 8 W microwave power, achieving gas temperatures as low as 27.5 °C—only 2 °C above ambient. Direct skin contacts with the plasma jet for 150 s resulted in a maximum temperature of 35 °C without discomfort. In addition, the MPJ significantly enhances the surface hydrophilicity of TPU, PVC, and POM materials without causing damage. The designed MPJ has low gas temperature and good discharge stability, providing a new solution for plasma surface modification of thermosensitive materials. Full article

(This article belongs to the Special Issue Recent Progress in Surface Treatment for Polymer Materials by Plasmas)

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21 pages, 6781 KiB

Open AccessArticle

Tensile and Structural Properties of Antioxidant- and CaCO₃-Modified Polyethylene Films

by Dmitry Myalenko, Olga Fedotova, Aleksandr Agarkov, Sergey Sirotin and Polina Poletaeva

Polymers 2025, 17(16), 2182; https://doi.org/10.3390/polym17162182 (registering DOI) - 9 Aug 2025

Abstract

The demand for modified packaging materials increases annually. At the same time, there is growing interest in the development of functional packaging. The incorporation of modifiers, stabilizers, and fillers into polymer matrices can enhance the functionality of the material but may also negatively [...] Read more.

The demand for modified packaging materials increases annually. At the same time, there is growing interest in the development of functional packaging. The incorporation of modifiers, stabilizers, and fillers into polymer matrices can enhance the functionality of the material but may also negatively affect its safety. Polymers are susceptible to degradation, which negatively affects their strength and tensile properties under external factors (physical, chemical or environmental). Packaging containing antimicrobial and antioxidant agents is among the most promising, as it contributes to the product quality during storage. Films based on calcium carbonate (CaCO₃) and dihydroquercetin (DHQ) remain insufficiently studied, despite their potential. Such materials are especially relevant for fatty products with a large contact surface area, including butter, cheese, and other solid high-fat foods. This study aimed to comprehensively investigate the structural and tensile properties of polyethylene films modified with varying contents of CaCO₃ and DHQ. The films were produced via blown film extrusion using a laboratory extruder (SJ-28). Surface analysis was performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Fourier-transform infrared (FTIR) spectroscopy was used to examine the film’s composition. The results showed that the introduction of more than 40.0 wt.% of CaCO₃ into the polymer base affected the strength properties. The conducted studies of the physical and mechanical properties of LDPE film samples filled with CaCO₃ showed significant changes in the samples containing more than 50.0 wt.% of the filler, with an increase in strength of more than 40.0%. The relative elongation at break after 50.0 wt.% decreased by more than 75.0%. These results indicate that to achieve the best strength properties for packaging materials, it is recommended to fill them to a maximum of 40.0 wt.%. The introduction of the antioxidant DHQ had almost no effect on the strength of the modified films. SEM analysis of films with high CaCO₃ content and DHQ revealed visible antioxidant particles on the film surface, suggesting enhanced antioxidant potential at the interface between the film and dairy products. AFM analysis confirmed that a CaCO₃ 40.0 wt.% content altered the surface roughness and heterogeneity of the films. FTIR spectroscopy revealed that the incorporation of CaCO₃ influenced the overall spectral profile of polyethylene, resulting in decreased peak intensities depending on the concentration of the filler. Based on these results, the modified polyethylene-based film with CaCO₃ and DHQ shows potential for use as food packaging with antioxidant properties. Full article

(This article belongs to the Section Polymer Membranes and Films)

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19 pages, 10057 KiB

Open AccessArticle

Investigations of the Sulfonated Poly(ether ether ketone) Membranes with Various Degrees of Sulfonation by Considering Durability for the Proton Exchange Membrane Fuel Cell (PEMFC) Applications

by Yinfeng Song, Zhenshuo Guo, Jiayi Yin, Mengjie Liu, Ivan Tolj, Sergey A. Grigoriev, Mingming Ge and Chuanyu Sun

Polymers 2025, 17(16), 2181; https://doi.org/10.3390/polym17162181 (registering DOI) - 9 Aug 2025

Abstract

The optimum degree of sulfonation (DS) for sulfonated poly(ether ether ketone) (SPEEK) membranes is determined by comprehensive characterization results, including proton conductivity, swelling ratio, water uptake, chemical stability, thermal stability, mechanical indicators, and proton exchange membrane fuel cell (PEMFC) performance. The PEMFC with [...] Read more.

The optimum degree of sulfonation (DS) for sulfonated poly(ether ether ketone) (SPEEK) membranes is determined by comprehensive characterization results, including proton conductivity, swelling ratio, water uptake, chemical stability, thermal stability, mechanical indicators, and proton exchange membrane fuel cell (PEMFC) performance. The PEMFC with a membrane electrode assembly containing a SPEEK-62 (DS = 62%) membrane realizes the power density of 482.08 mW/cm², surpassing that of commercial Nafion-212 under identical conditions. In the crucial Fenton test for durability, the SPEEK-51 membrane demonstrated outstanding dimensional and chemical stability, with a decomposition time of up to 137 min, far surpassing the durability of SPEEK-62 or other membranes with a higher DS. The results indicate that in comparison to the SPEEK-67 membrane as reported in the literature, SPEEK membranes with a DS = 51~62% hold great potential for future applications in PEMFC, and further modifications of these membranes can be a promising approach to enhance the conductivity while maintaining good chemical stability. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membrane Fuel Cells: Technology and Applications)

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16 pages, 2276 KiB

Open AccessArticle

Mechanical Behavior Analysis of Polypropylene-Based Composites and a Photopolymer Resin via Tensile and Scratch Testing

by Sergiu Gabriel Pal, Viorel Goanta, Ciprian Ionut Moraras and Vlad Carlescu

Polymers 2025, 17(16), 2180; https://doi.org/10.3390/polym17162180 (registering DOI) - 9 Aug 2025

Abstract

This study investigates the mechanical behavior of various plastic materials through tensile and scratch testing. Three polypropylene-based composites—PP-GB30GF10, PP-TD40, and PP-GF20—were subjected to uniaxial tensile tests in accordance with standard protocols to assess their strength, stiffness, and elongation characteristics. The results highlight notable [...] Read more.

This study investigates the mechanical behavior of various plastic materials through tensile and scratch testing. Three polypropylene-based composites—PP-GB30GF10, PP-TD40, and PP-GF20—were subjected to uniaxial tensile tests in accordance with standard protocols to assess their strength, stiffness, and elongation characteristics. The results highlight notable differences in the tensile performance depending on the type and percentage of reinforcing fillers, such as glass fibers and talc. In parallel, the scratch resistance was evaluated for specimens produced via stereolithography (SLA) using Formlabs Black V4 resin, a common photopolymer used in prototyping applications. The scratch test aimed to characterize the surface durability under localized mechanical stress. The findings contribute to a better understanding of the mechanical performance of these materials and their potential applications in fields requiring both structural integrity and surface resilience, such as automotive components and functional prototyping. Full article

(This article belongs to the Section Polymer Applications)

12 pages, 1563 KiB

Open AccessArticle

Tough Hydrogel Reinforced by Meta-Aramid Nanofibers for Flexible Sensors

by Zhiwen Hou, Yongzheng Li, Donghao Zhang, Cun Peng, Yan Wang and Kunyan Sui

Polymers 2025, 17(16), 2179; https://doi.org/10.3390/polym17162179 (registering DOI) - 9 Aug 2025

Abstract

Hydrogels exhibit significant promise for advanced flexible sensing applications owing to their intrinsic softness, biocompatibility, and customizable functionalities. Nevertheless, their limited mechanical strength poses a critical barrier to practical implementation. In this study, we engineered a mechanically robust alginate/chitosan (SA/CS) hydrogel reinforced with [...] Read more.

Hydrogels exhibit significant promise for advanced flexible sensing applications owing to their intrinsic softness, biocompatibility, and customizable functionalities. Nevertheless, their limited mechanical strength poses a critical barrier to practical implementation. In this study, we engineered a mechanically robust alginate/chitosan (SA/CS) hydrogel reinforced with meta-aramid (PMIA) nanofibers. The resulting composite hydrogel achieves a tensile strength of 16.8 MPa, substantially exceeding the performance of conventional biomass-derived hydrogels. When employed as a flexible sensor, the hydrogel demonstrates exceptional pressure-sensing capabilities, featuring high sensitivity (178.41 MΩ/MPa below 5 kPa), rapid response kinetics (0.4–0.8 s), and sustained stability (>200 cycles). Leveraging these properties, we successfully monitored vocal cord vibrations and finger motion trajectories, highlighting their potential for biomechanical sensing applications. Full article

(This article belongs to the Special Issue New Polymeric Nanomaterials: Optimization and Application in the Field of Environmental Sensors)

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13 pages, 693 KiB

Open AccessArticle

Effect of Recycling on the Thermal and Rheological Properties of PP/MWCNT Composites Used as Liner Materials

by Attila Bata, Ferenc Ronkay, Caizhi Zhang and Péter Gerse

Polymers 2025, 17(16), 2178; https://doi.org/10.3390/polym17162178 - 8 Aug 2025

Abstract

In this study, we developed polypropylene-based nanocomposites using different (0.3, 0.5, and 1 wt%) fillers of multi-walled carbon nanotubes (MWCNTs), with a particular focus on their applicability as lining materials for Type IV hydrogen storage tanks. The aim of this research was to [...] Read more.

In this study, we developed polypropylene-based nanocomposites using different (0.3, 0.5, and 1 wt%) fillers of multi-walled carbon nanotubes (MWCNTs), with a particular focus on their applicability as lining materials for Type IV hydrogen storage tanks. The aim of this research was to improve the thermal stability and rheological behavior of PP, while also evaluating the recyclability of the resulting composites in order to support sustainability goals. A realistic recycling approach was simulated by producing original and regranulated (REG) samples using a twin-screw extruder. Thermal analysis showed that the incorporation of MWCNTs promoted crystallization, increasing both the degree of crystallinity and lamellar thickness, which are beneficial factors in terms of reducing gas permeability. Rheological tests showed increased storage and loss moduli in both nanocomposites and their recycled counterparts, especially at low frequencies. It is noteworthy that in REG samples with 0.3 and 1 wt% content, the zero-shear viscosity increased by approximately 50% and 90%, respectively, compared to pure PP. In our research, we produced nanocomposites that could offer significant advances in the field of hydrogen storage and liner materials, while the results of the regranulated composites could further enhance the sustainability of our materials. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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24 pages, 2980 KiB

Open AccessArticle

Study on a Rheological Constitutive Model with Yield and Aging Effects for Polyethylene Gas Pipes

by Rui-Hua Yin, Si-Xi Zha, Jun-Qiang Wang and Hui-Qing Lan

Polymers 2025, 17(16), 2177; https://doi.org/10.3390/polym17162177 - 8 Aug 2025

Abstract

Constitutive models and deformation behaviors for polymer materials have long been complex and are always a hot research focus. As a typical semi-crystalline polymer, polyethylene (PE) gas pipes exhibit pronounced nonlinearity, strain dependence, and time dependence during long-term service. Simple material models fail [...] Read more.

Constitutive models and deformation behaviors for polymer materials have long been complex and are always a hot research focus. As a typical semi-crystalline polymer, polyethylene (PE) gas pipes exhibit pronounced nonlinearity, strain dependence, and time dependence during long-term service. Simple material models fail to capture the scale-dependent characteristics of the PE pipes, resulting in difficulties in accurately describing and simulating their deformation and damage behavior. Currently, some PE gas pipes have entered the mid-to-late stages of service life, so it is necessary to propose a constitutive model representing their complex mechanical behavior for simulation and performance evaluation purposes. Based on results from aging tests, tensile tests, differential scanning calorimetry, and Fourier-transform infrared spectroscopy, this study proposes a method to select a rheological framework and a constitutive model that couples thermo-oxidative aging effects in PE gas pipes. The model is developed within the widely recognized rheological framework and is grounded in continuum mechanics, continuum damage mechanics, and the aging behavior of polymer materials. This method and model are suitable for characterizing the mechanical dependency of PE pipes and demonstrate strong fitting performance. According to the calculation results, the goodness of fit of this constitutive model for the uniaxial tensile test results at the different aging times ranges from 0.982 to 0.999. The findings provide theoretical support for the simulation and service life prediction for PE pipelines. Full article

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

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22 pages, 3060 KiB

Open AccessArticle

Predictive Analysis of the Mechanical Properties of Biopolymer–Fiber-Reinforced Composite-Stabilized Soil Based on Genetic Algorithm-Optimized Back Propagation Neural Networks

by Guotao Wei, Zhaoping Wang, Xuanhao Cao and Jiuran Wen

Polymers 2025, 17(16), 2176; https://doi.org/10.3390/polym17162176 - 8 Aug 2025

Abstract

The limitations imposed by the inherent complexity of multi-component composition ratios in biological polymer-stabilized soils have hindered rapid and accurate performance prediction. To enhance the predictive accuracy for biopolymer–fiber-stabilized soils, an optimized GA-driven backpropagation (BP) neural network was developed. Three key factors influencing [...] Read more.

The limitations imposed by the inherent complexity of multi-component composition ratios in biological polymer-stabilized soils have hindered rapid and accurate performance prediction. To enhance the predictive accuracy for biopolymer–fiber-stabilized soils, an optimized GA-driven backpropagation (BP) neural network was developed. Three key factors influencing mechanical strength (guar gum (GG), xanthan gum (XG), and polybutylene succinate (PBS)) were identified. The global optimization capability of GA was utilized to construct an integrated GA-BP model, with these factors serving as inputs and 7d compressive strength as the output. Support vector machine (SVM) was also incorporated to provide a benchmark comparison of predictive performance. Validation was performed using 80% of the dataset, with the remaining 20% used for testing. The optimal biopolymer dosage was found to be within the range of 0.5% to 1.0%, and the maximum 7d compressive strength achieved was 466.67 kPa at the 0.5% XG–0.5% GG combination, representing a 273% increase over untreated soil. The GA-BP model demonstrated superior performance in terms of prediction accuracy and stability, as indicated by an R² of 0.887—significantly higher than those of the BP (0.714) and SVM (0.554) models. The mean squared error was substantially reduced to 1413, compared to 2130 and 3113 for BP and SVM, respectively. Although MAPE approached those of the GA-BP, the overall predictive efficacy of SVM was found to be inferior. A reliable and robust methodology for forecasting the mechanical behavior of stabilized soils has thus been provided by this model, supporting advanced applications within geotechnical engineering. Full article

(This article belongs to the Special Issue Preparation, Structure and Characterization of Polymer/Cement Composites—3rd Edition)

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27 pages, 3616 KiB

Open AccessArticle

Structural and Material Optimization of a Sensor-Integrated Autonomous Aerial Vehicle Using KMU-3 CFRP

by Yerkebulan Nurgizat, Arman Uzbekbayev, Igor Fedorov, Andrey Bebenin and Andrey Karypov

Polymers 2025, 17(16), 2175; https://doi.org/10.3390/polym17162175 - 8 Aug 2025

Abstract

This study addresses the selection and application of composite materials for aerospace systems operating in extreme environmental conditions, with a particular focus on high-altitude pseudo-satellites (HAPS). This research is centered on the development of a 400 kg autonomous aerial vehicle (AAV) capable of [...] Read more.

This study addresses the selection and application of composite materials for aerospace systems operating in extreme environmental conditions, with a particular focus on high-altitude pseudo-satellites (HAPS). This research is centered on the development of a 400 kg autonomous aerial vehicle (AAV) capable of sustained operations at altitudes of up to 30 km. KMU-3’s microstructure, comprising high-modulus carbon fibers (5–7 µm diameter) in a 5-211B epoxy matrix, provides a high specific strength (1000–2500 MPa), low density (1.6–1.8 g/cm³), and thermal stability (−60 °C to +600 °C), ensuring structural integrity in stratospheric conditions. The mechanical, thermal, and aerodynamic properties of KMU-3-based truss structures were evaluated using finite element method (FEM) simulations, computational fluid dynamics (CFD) analysis, and experimental prototyping. The results indicate that ultra-thin KMU-3 with a wall thickness of 0.1 mm maintains structural integrity under dynamic loads while minimizing overall mass. A novel thermal bonding technique employing 5-211B epoxy resin was developed, resulting in joints with a shear strength of 40 MPa and fatigue life exceeding 10⁶ cycles at 50% load. The material properties remained stable across the operational temperature range of −60 °C to +80 °C. An optimized fiber orientation (0°/90° for longerons and ±45° for diagonals) enhanced the resistance to axial, shear, and torsional stresses, while the epoxy matrix ensures radiation resistance. Finite element method (FEM) and computational fluid dynamics (CFD) analyses, validated by prototyping, confirm the performance of ultra-thin (0.1 mm) truss structures, achieving a lightweight (45 kg) design. These findings provide a validated, lightweight framework for next-generation HAPS, supporting extended mission durations under harsh stratospheric conditions. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

14 pages, 3600 KiB

Open AccessArticle

Edible Films Based on Fish Gelatin and Soluble Soybean Polysaccharide Enriched with Tea Polyphenol for Active Food Packaging

by Jie Liu, Zhongfeng Song, Yiwei Wang, Ying Pei and Keyong Tang

Polymers 2025, 17(16), 2174; https://doi.org/10.3390/polym17162174 - 8 Aug 2025

Abstract

The increasing demand for environmentally friendly alternatives to conventional plastic packaging has driven interest in the development of biodegradable edible films with functional properties. In this work, edible blend films were developed based on fish gelatin (FG), soluble soybean polysaccharide (SSPS), and tea [...] Read more.

The increasing demand for environmentally friendly alternatives to conventional plastic packaging has driven interest in the development of biodegradable edible films with functional properties. In this work, edible blend films were developed based on fish gelatin (FG), soluble soybean polysaccharide (SSPS), and tea polyphenol (TP) for active food packaging applications. The FG/SSPS/TP films were prepared by solvent casting and characterized in terms of their structural, mechanical, optical, thermal, and barrier properties. FTIR, SEM, and XRD analyses revealed TP-induced morphological and structure changes in the biopolymer matrix. The incorporation of TP significantly enhanced the antioxidant activity and UV-shielding properties of the films, while also modifying their flexibility and surface hydrophilicity. The packaging performance of FG/SSPS/TP films was evaluated using beef tallow as a model food product. Compared to neat FG/SSPS and polyethylene films, the FG/SSPS/TP films effectively suppressed lipid oxidation of the samples during storage. The results demonstrated that the prepared FG/SSPS/TP films possess strong potential for use as edible and active packaging materials for food products. Full article

(This article belongs to the Special Issue Smart and Active Food Packaging Systems Based on Natural Polymers)

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19 pages, 6153 KiB

Open AccessArticle

Copper–PLLA-Based Biopolymer Wrinkle Structures for Enhanced Antibacterial Activity

by Petr Slepička, Iva Labíková, Bára Frýdlová, Aneta Pagáčová, Nikola Slepičková Kasálková, Petr Sajdl and Václav Švorčík

Polymers 2025, 17(16), 2173; https://doi.org/10.3390/polym17162173 - 8 Aug 2025

Abstract

The increasing prevalence of antibiotic-resistant bacteria has intensified the need for innovative antibacterial surfaces, particularly in biomedical applications. Traditional approaches often rely on chemical agents alone, which may lead to diminishing efficacy over time. To address this, we investigated the development of a [...] Read more.

The increasing prevalence of antibiotic-resistant bacteria has intensified the need for innovative antibacterial surfaces, particularly in biomedical applications. Traditional approaches often rely on chemical agents alone, which may lead to diminishing efficacy over time. To address this, we investigated the development of a novel antibacterial surface by combining the inherent antimicrobial properties of copper with an engineered surface topography on a biopolymer matrix. A copper–poly-L-lactic acid (Cu-PLLA) composite system was fabricated using sputtering deposition followed by controlled thermal treatment to induce wrinkle-like micro- and nanostructures on the surface. The surface morphology was characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM), confirming the formation of hierarchical wrinkle patterns. The chemical composition and distribution of copper were analyzed via energy-dispersive X-ray spectroscopy (EDS). Antibacterial performance was assessed against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus using standard colony count reduction assays. The Cu-PLLA wrinkled surfaces demonstrated significantly enhanced bactericidal activity compared with flat PLLA and copper-free controls, a finding attributed to a synergistic effect of mechanical membrane disruption and copper-mediated chemical toxicity. These findings suggest that biopolymer–metal hybrid surfaces with engineered topography offer a promising strategy for developing next-generation antibacterial materials suitable for biomedical and clinical use. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Science and Technology)

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33 pages, 13337 KiB

Open AccessArticle

Machinability of Basalt and Glass Fiber Hybrid Composites in Dry Drilling Using TiN/TiAlN-Coated Drill Bits

by Mehmet İskender Özsoy, Satılmış Ürgün, Sinan Fidan, Eser Yarar, Erman Güleç and Mustafa Özgür Bora

Polymers 2025, 17(16), 2172; https://doi.org/10.3390/polym17162172 - 8 Aug 2025

Abstract

Drilling-induced damage in fiber-reinforced polymer composite materials was measured excavating four laminates, basalt (B₁₄), glass (G₁₄) and their two sandwich type hybrids (B₄G₆B₄, G₄B₆G₄), with 6 mm [...] Read more.

Drilling-induced damage in fiber-reinforced polymer composite materials was measured excavating four laminates, basalt (B₁₄), glass (G₁₄) and their two sandwich type hybrids (B₄G₆B₄, G₄B₆G₄), with 6 mm twist drills at 1520 revolutions per minute and 0.10 mm rev⁻¹ under dry running with an uncoated high-speed steel (HSS-R), grind-coated high-speed steel (HSS-G) or physical vapor deposition-coated (high-speed steel coated with Titanium Nitride (TiN) and Titanium Aluminum Nitride (TiAlN)) drill bits. The hybrid sheets were deliberately incorporated to clarify how alternating basalt–glass architectures redistribute interlaminar stresses during drilling, while the hard, low-friction TiN and TiAlN ceramic coatings enhance cutting performance by forming a heat-resistant tribological barrier that lowers tool–workpiece adhesion, reduces interface temperature, and thereby suppresses thrust-induced delamination. Replacement of an uncoated, grind-coated, high-speed-steel drill (HSS-G) with the latter coats lowered the mechanical and thermal loads substantially: mean thrust fell from 79–94 N to 24–30 N, and peak workpiece temperatures from 112 °C to 74 °C. Accordingly, entry/exit oversize fell from 2.5–4.7% to under 0.6% and, from the surface, the SEM image displayed clean fiber severance rather than pull-out and matrix smear. By analysis of variance (ANOVA), 92.7% of the variance of thrust and 86.6% of that of temperature could be accounted for by the drill-bit factor, thus confirming that the coatings overwhelm the laminate structure and hybrid stacking simply redistribute, but cannot overcome, the former influence. Regression models and an artificial neural network optimized via meta-heuristic optimization foretold thrust, temperature and delamination with an R² value of 0.94 or higher, providing an instant-screening device with which to explore industrial application. The work reveals TiAlN- and TiN-coated drills as financially competitive alternatives with which to achieve ±1% dimensional accuracy and minimum subsurface damage during multi-material composite machining. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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