Polymers

15 pages, 4576 KB

Open AccessEditor’s ChoiceArticle

Impedance-Matched Iron-Added Polymeric Composite Film Incorporated with Iron Nanowire for Electromagnetic Absorption Application

by Yuh-Jing Chiou, Pei-Jung Chang, Pei-Ru Su, Sheng-Jung Tsou and Chung-Kwei Lin

Polymers 2025, 17(21), 2965; https://doi.org/10.3390/polym17212965 - 6 Nov 2025

Viewed by 578

Abstract

Salisbury screen-type radar absorption structures (RASs) consisting of a resistance sheet, a spacer, and a conductive base provide an efficient method for microwave absorption. An impedance-matched resistance sheet allows microwaves to enter, whereas superior microwave absorbers enhance their performance further. In the present [...] Read more.

Salisbury screen-type radar absorption structures (RASs) consisting of a resistance sheet, a spacer, and a conductive base provide an efficient method for microwave absorption. An impedance-matched resistance sheet allows microwaves to enter, whereas superior microwave absorbers enhance their performance further. In the present work, an impedance matching composite film was prepared by using polymer/iron/iron nanowires. By varying the polymer, poly (methyl methacrylate) (PMMA), poly (vinylidene fluoride) (PVDF), and poly (vinyl alcohol) (PVA), to iron powder ratios (1:1, 2:1, and 4:1), composite films were synthesized and examined by scanning electron microscopy, X-ray diffraction, and the four-point probe method to determine the materials’ characteristics. An impedance-matched composite film was prepared based on the selected composition with 1–10 wt.% iron nanowire additions. Experimental results showed that the polymeric composite film prepared by a ratio of iron-PVA of 4:1 exhibited a sheet resistance of 49 ± 9.7 Ω/sq due to well dispersion of iron powder in PVA. With 1 wt.% Fe nanowire addition, the optimal composite sheet resistance was 329.7 ± 45.3 Ω/sq, which corresponded to an impedance matching degree (i.e., |Z_in/Z₀| value) of 0.88 ± 0.12 and can be used as a resistance sheet for a Salisbury screen-type absorber in RAS applications. Full article

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

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23 pages, 1696 KB

Open AccessReview

Chitosan-Grafted Graphene Oxide-Reinforced Bio-Based Waterborne Epoxy Nanocomposites for Antibacterial and Corrosion Resistance in Tropical Marine Environments: A Mini-Review

by Yunyang Wu, Zhongyuan Luo, Yucheng Wang, Chengwei Xu and Yuanzhe Li

Polymers 2025, 17(21), 2964; https://doi.org/10.3390/polym17212964 - 6 Nov 2025

Viewed by 768

Abstract

Epoxy resin coatings are widely employed for steel protection owing to their excellent adhesion, chemical stability, mechanical strength, and barrier properties. However, conventional bisphenol A-based resins and organic solvents may pose risks to reproductive, developmental, and immune systems, as well as contribute to [...] Read more.

Epoxy resin coatings are widely employed for steel protection owing to their excellent adhesion, chemical stability, mechanical strength, and barrier properties. However, conventional bisphenol A-based resins and organic solvents may pose risks to reproductive, developmental, and immune systems, as well as contribute to atmospheric pollution. This mini-review critically evaluates recent advancements in fully waterborne bio-based epoxy nanocomposites as sustainable alternatives, with particular emphasis on their enhanced antibacterial and corrosion-resistant performance in tropical marine environments. A central focus is the role of chitosan-grafted graphene oxide (Chi-GO) as a multifunctional nanofiller that significantly enhances both antibacterial efficacy and barrier capabilities. For instance, coatings reinforced with Chi-GO exhibit up to two orders of magnitude lower corrosion current density than pristine epoxy coatings, and achieve over 95% bacterial inhibition against Escherichia coli and Staphylococcus aureus at a 1 wt.% loading. The review summarizes key synthesis methods, functional modification techniques, and commonly adopted evaluation approaches. Emerging research further underscores environmental performance metrics, including reduced volatile organic compound (VOC) emissions and improved life-cycle assessments. By integrating bio-based polymer matrices with Chi-GO, these composite systems present a promising pathway toward environmentally benign and durable protective coatings. Nevertheless, critical challenges concerning scalability and long-term stability under real-world operating conditions remain insufficiently addressed. Future research should emphasize scalable manufacturing strategies, such as roll-to-roll processing, and conduct extended tropical exposure testing (e.g., salt spray tests beyond 2000 h). Additionally, developing comprehensive life-cycle assessment (LCA) frameworks will be crucial for sustainable industrial implementation. Full article

(This article belongs to the Special Issue Polymers for Protective Coatings)

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20 pages, 2492 KB

Open AccessArticle

Polyethylene and Polypropylene Pyrolysis Using Fe³⁺-Modified Kaolin Catalyst for Enhanced Gas and Pyrolysis Oil Production

by Sergey Nechipurenko, Binara Dossumova, Sergey Efremov, Nazar Zabara, Aigerim Kaiaidarova, Olga Ibragimova, Anara Omarova, Fedor Pogorov and Diyar Tokmurzin

Polymers 2025, 17(21), 2963; https://doi.org/10.3390/polym17212963 - 6 Nov 2025

Viewed by 1008

Abstract

Calcined and acid-leached kaolin impregnated with Fe(NO₃)₃·9H₂O (6.6 wt. % Fe₂O₃) was developed as an inexpensive bifunctional catalyst for the slow fixed-bed pyrolysis of polypropylene (PP) and low-density polyethylene (LDPE). Experiments were run [...] Read more.

Calcined and acid-leached kaolin impregnated with Fe(NO₃)₃·9H₂O (6.6 wt. % Fe₂O₃) was developed as an inexpensive bifunctional catalyst for the slow fixed-bed pyrolysis of polypropylene (PP) and low-density polyethylene (LDPE). Experiments were run with catalyst-to-plastic mass ratios of 1:4, 1:2, and 1:1 in a quartz tube reactor heated from 25 to 800 °C. For PP, increasing the Fe/kaolin loading progressively raised non-condensable gas from 26 wt. % to 44 wt. % and drove liquid aromatics from 27.9% to 72.3%, while combined paraffins olefins fell to 2.5% and wax exhibited a 46 → 24 → 36 wt. % trend. In contrast, LDPE at a 1:4 ratio already yielded 56 wt. % oil and only 22 wt. % wax; further catalyst addition mainly enhanced CH₄/CO-rich pyrolysis gas (PyGas) and char without substantially boosting aromatics. Gas analysis confirmed that Fe₂O₃ reduction and kaolin de-hydroxylation generated in situ H₂O, CO, and H₂. Given the catalyst’s low cost, regenerability, and ability to valorize the two most abundant waste polyolefins within the same reactor, the process offers a scalable route to flexible fuel and gas production from mixed plastic streams. Full article

(This article belongs to the Section Circular and Green Sustainable Polymer Science)

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21 pages, 6648 KB

Open AccessArticle

Tailoring PBT Performance Through PBT/POE-g-GMA Nanocomposites with MWCNT

by Eduardo da Silva Barbosa Ferreira, Elieber Barros Bezerra, Carlos Bruno Barreto Luna, Edson Antonio dos Santos Filho, Renate Maria Ramos Wellen and Edcleide Maria Araújo

Polymers 2025, 17(21), 2962; https://doi.org/10.3390/polym17212962 - 6 Nov 2025

Viewed by 608

Abstract

The production of polymer nanocomposites from supertough blends reinforced with carbon-based nanofillers has garnered attention in recent years due to improvements in their mechanical, thermal, and electrical properties. Currently, the main challenge is to develop materials with balanced performance for diverse industrial demands. [...] Read more.

The production of polymer nanocomposites from supertough blends reinforced with carbon-based nanofillers has garnered attention in recent years due to improvements in their mechanical, thermal, and electrical properties. Currently, the main challenge is to develop materials with balanced performance for diverse industrial demands. In this context, this work aimed to produce nanocomposites of poly(butylene terephthalate) (PBT) and poly(ethylene-octene) grafted with glycidyl methacrylate (POE-g-GMA), reinforced with carbon nanotubes (MWCNTs). The PBT, the PBT/POE-g-GMA blend, and the respective MWCNT nanocomposites were initially premixed in an internal mixer and then processed in a co-rotational twin-screw extruder. After processing, they were injection-molded to obtain tensile, impact, and HDT test specimens. Mechanical (tensile, impact, and Shore D hardness), thermal (differential scanning calorimetry—DSC), thermomechanical (heat deflection temperature—HDT), electrical resistivity/conductivity, morphology, and Fourier transform infrared spectroscopy (FTIR) properties were evaluated. The results demonstrated a good balance among the investigated properties, with improvements in mechanical, thermal, and thermomechanical properties when compared to PBT. The impact strength of the nanocomposites reached 186 J/m, approximately 158% higher than that of neat PBT. The HDT reached approximately 55 °C in the PBT/POE-g-GMA/MWCNT5 nanocomposites, while the crystallization temperature increased by 11 °C, as evidenced by DSC, an aspect of great relevance for industrial applications. Furthermore, the PBT/POE-g-GMA/MWCNT5 nanocomposites exhibited an electrical conductivity of 1.06 × 10⁻⁷ S/cm, indicating potential for electrical applications. Full article

(This article belongs to the Special Issue Mechanical and Dynamic Characteristics of Polymers and Polymer Composites)

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17 pages, 2104 KB

Open AccessArticle

Predicting Packaging Material–Food Interactions and the Respective Migration and Permeation Based on Hansen Solubility Parameters—A Case Study of Bio-Based Polyester Cutin

by Costas Tsioptsias, Athanasios Goulas, Maria Tsini, Athanasia Zoglopiti, Anna Marinopoulou and Vassilis Karageorgiou

Polymers 2025, 17(21), 2961; https://doi.org/10.3390/polym17212961 - 6 Nov 2025

Viewed by 637

Abstract

One of the current and serious environmental problems is the pollution due to microplastics. There is an urgent need for biodegradable and bio-based materials for numerous applications, including food packaging. In this work we examine the bio-based polyester cutin for its potential to [...] Read more.

One of the current and serious environmental problems is the pollution due to microplastics. There is an urgent need for biodegradable and bio-based materials for numerous applications, including food packaging. In this work we examine the bio-based polyester cutin for its potential to be used as food packaging material, in terms of migration, based on the Hansen Solubility Parameters (HSP). Cutin is a cross-linked polymer that is swelled by various solvents. We use the degree of swelling of cutin in carefully selected solvents of various polarities in order to estimate the HSP of cutin. Some solvents can induce alteration of the chemical structure of cutin, as proven by Fourier Transform Infrared (FTIR) measurements. This interferes with the process of estimation of the HSP and is discussed in depth. The distance R_a and the Relative Energy Difference (RED) between the HSP of cutin and various food components are calculated and used to predict the existence of favorable interactions between cutin and the food components, which is translated to a high probability for the existence of migration and permeation. Experimental confirmation of one prediction based on HSP is provided by UV-VIS photometry. Similar calculations were performed for other polyesters (poly(lactic acid) and poly(hydroxy butyrate)). Cutin exhibits compatibility with substances of low polarity, such as fats and lipids and non-polar compounds found in essential oils. Thus, migration into fatty foods is expected as well as sorption and permeation of some (volatile) compounds into cutin. Nevertheless, we conclude that the overall migration risk for cutin is lower than the one of other bio-based polyesters. HSP can be used for initial screening of potential migration risks; however, further research is necessary in order to assess the occurrence, extent, and significance of the actual migration. Full article

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

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17 pages, 8309 KB

Open AccessArticle

Green Synthesis of Chitosan Silver Nanoparticle Composite Materials: A Comparative Study of Microwave and One-Pot Reduction Methods

by Ahmed Hosney, Algimanta Kundrotaitė, Donata Drapanauskaitė, Marius Urbonavičius, Šarūnas Varnagiris, Sana Ullah and Karolina Barčauskaitė

Polymers 2025, 17(21), 2960; https://doi.org/10.3390/polym17212960 - 6 Nov 2025

Viewed by 1041

Abstract

Green synthesis methods of silver nanoparticles have gained great attention because they offer sustainable, eco-friendly, and less-toxic alternatives to traditional methods. This study sheds light on the green synthesis of chitosan silver nanoparticle composites, providing a comparative evaluation of microwave-assisted (M1) and a [...] Read more.

Green synthesis methods of silver nanoparticles have gained great attention because they offer sustainable, eco-friendly, and less-toxic alternatives to traditional methods. This study sheds light on the green synthesis of chitosan silver nanoparticle composites, providing a comparative evaluation of microwave-assisted (M1) and a one-pot (M2) reduction methods. The morphological, crystallinity, and structural uniformity characteristics were evaluated by UV-Visible, Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) with employing image processing pipeline based on deep learning model for segmentation and particles size estimation. The UV-visible spectrum exhibited independent SPR peaks ranging from 400 to 450 nm for all samples; however, microwave assisted-synthesis possessed narrower and more intense peaks indicative of better crystallinity and mono-dispersity. SEM depicted smaller, more uniformly dispersed particles for microwave-assisted (M1), while deep learning segmentation showed lower particle size variability (σ ≈ 24–43 nm), compared to polydisperse (σ ≈ 16–59 nm) in M2 samples. XRD showed crystalline face-centered cubic (FCC) silver with dominant peaks in M1 samples, whereas M2 had broader, less intense peaks with amorphous features. Raman vibrations revealed more structural order and homogenous capping in M1 than M2. Therefore, microwave-assisted (M1) showed better control on nucleation, particle size, crystallinity, and homogeneity due to a faster and uniform energy distribution. The future research would focus on the antimicrobial evaluation of such nanoparticles in agronomy. Full article

(This article belongs to the Special Issue Functional Chitosan-Based Nanocomposites: Synthesis, Characterization and Applications)

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25 pages, 6570 KB

Open AccessArticle

Analytical Analysis of Recirculating Flow in Single-Screw Extruders

by Chris Rauwendaal

Polymers 2025, 17(21), 2959; https://doi.org/10.3390/polym17212959 - 6 Nov 2025

Viewed by 511

Abstract

Current analytical theories of recirculating flow in single-screw extruders consider only cross-channel flow in channels of infinite width with only one exception. Proper analysis of recirculating flow requires inclusion of normal velocities and the effect of finite channel width. More broadly, this paper [...] Read more.

Current analytical theories of recirculating flow in single-screw extruders consider only cross-channel flow in channels of infinite width with only one exception. Proper analysis of recirculating flow requires inclusion of normal velocities and the effect of finite channel width. More broadly, this paper presents an analytical description of lid-driven cavity flow—one of the most frequently studied flows in fluid dynamics. Expressions for velocities and flow rates for Newtonian fluids are obtained that satisfy the balance equations. These expressions have been compared to results of numerical analyses with good agreement. Flow rates and velocities are displayed with 3D surface plots and contour plots. These plots provide better insight into the flow behavior than 2D graphs. We have analyzed flow in slit channels with width much greater than the height (

W > > H

) and flow in a square channel (

W = H

). The vortex center (stagnation point) in a slit channel is located at normal coordinate

ψ = 2 / 3

. The vortex center in a square channel is located at

ψ = 0.76

. These analytical results allow for the development of better analytical models for melt temperature distribution, mixing, and devolatilization in single-screw extruders. Full article

(This article belongs to the Special Issue Advances in Screw Processing of Polymeric Materials - In Memory of Professor James Lindsay White)

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14 pages, 2296 KB

Open AccessArticle

Detection of Filtration Characteristics of Nontraditional Asymmetric Microporous Membranes Using Size-Controllable Micro-Hydrogel

by Hao Zhang, Tiantian Zhu, Yushan Zheng, Weiheng Liu, Tangxin Zhang, Yuhua Mao, Jiayuan Wang, Lingyu Zhu, Cheng Xu and Jianli Wang

Polymers 2025, 17(21), 2958; https://doi.org/10.3390/polym17212958 - 6 Nov 2025

Cited by 1 | Viewed by 467

Abstract

Microporous membranes are frequently used to remove or concentrate suspended solids. To maximize filtration efficiency for certain high-value liquids, a microporous membrane with a nontraditional asymmetric topology was recently developed to treat bio-based liquids, such as the isolation of proteins/enzymes from concentrates or [...] Read more.

Microporous membranes are frequently used to remove or concentrate suspended solids. To maximize filtration efficiency for certain high-value liquids, a microporous membrane with a nontraditional asymmetric topology was recently developed to treat bio-based liquids, such as the isolation of proteins/enzymes from concentrates or the concentration of active cells from cultivation media. In this study, compared with both asymmetric and symmetric membranes, we reveal the unique filtration properties of “upper-stream open” asymmetric membrane using four types of fluids comprising monodispersed micro-hydrogels with sizes ranging from 294 to 517 nm. The results indicate that the internal pore structures of the membranes significantly affect the retention of microhydrogels of identical sizes. Asymmetric membranes offer considerable advantages in terms of retention efficiency and particle localization. By applying four classical blocking models along with adsorption models, the primary blockage mechanisms in asymmetric membranes for microgels of different sizes were explored. These results offer a better understanding of the interaction between the membrane and filtrate, assist in membrane selection, and elucidate the experimental results of membrane filtration. Full article

(This article belongs to the Special Issue Advances in Multifunctional Polymer-Based Nanocomposites, 2nd Edition)

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22 pages, 6324 KB

Open AccessArticle

A Novel Approach for the Estimation of the Efficiency of Demulsification of Water-In-Crude Oil Emulsions

by Slavko Nešić, Olga Govedarica, Mirjana Jovičić, Julijana Žeravica, Sonja Stojanov, Cvijan Antić and Dragan Govedarica

Polymers 2025, 17(21), 2957; https://doi.org/10.3390/polym17212957 - 6 Nov 2025

Viewed by 665

Abstract

Undesirable water-in-crude oil emulsions in the oil and gas industry can lead to several issues, including equipment corrosion, high-pressure drops in pipelines, high pumping costs, and increased total production costs. These emulsions are commonly treated with surface-active chemicals called demulsifiers, which can break [...] Read more.

Undesirable water-in-crude oil emulsions in the oil and gas industry can lead to several issues, including equipment corrosion, high-pressure drops in pipelines, high pumping costs, and increased total production costs. These emulsions are commonly treated with surface-active chemicals called demulsifiers, which can break an oil–water interface and enhance phase separation. This study introduces a novel approach based on neural networks to estimate demulsification efficiency and to aid in the selection of demulsifiers under field conditions. The influence of various types of demulsifiers, demulsifier concentration, time required for demulsification, temperature and asphaltene content on the demulsification efficiency is analyzed. To improve model accuracy, a modified full-scale factorial design of experiments and the comparison of response surface method with multilayer perception neural networks were conducted. The results demonstrated the advantages of using neural networks over the response surface methodology such as a reduced settling time in separators, an improved crude oil dehydration and processing capacity, and a lower consumption of energy and utilities. The findings may enhance processing conditions and identify regions of higher demulsification efficiency. The neural network approach provided a more accurate prediction of maximum of demulsification efficiency compared to the response surface methodology. The automated multilayer perceptron neural network, with an architecture consisting of 3 input layers, 14 hidden layers, and 1 output layer, demonstrated the highest validation performance R² of 0.991932 by utilizing a logistic output activation function and a hyperbolic tangent activation function for the hidden layers. The identification of shifted optimal values of time required from demulsification, demulsifier concentration, and asphaltene content along with sensitivity analysis confirmed advantages of automated neural networks over conventional methods. Full article

(This article belongs to the Special Issue Polymer Science in Petroleum Engineering: Latest Trends and Developments)

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12 pages, 932 KB

Open AccessArticle

Partition Function Zeros and Heat Capacity Decomposition Reveal HP Protein Foldability

by Sing-Shuo Huang and Chi-Ning Chen

Polymers 2025, 17(21), 2956; https://doi.org/10.3390/polym17212956 - 6 Nov 2025

Viewed by 432

Abstract

The heat capacity decomposition method, a well-established analytical approach in polymer thermodynamics for elucidating thermal transitions in homogeneous polymers, is extended here to heterogeneous systems. We demonstrate that the decomposition of heat capacity based on partition function zeros allows the identification of transition-like [...] Read more.

The heat capacity decomposition method, a well-established analytical approach in polymer thermodynamics for elucidating thermal transitions in homogeneous polymers, is extended here to heterogeneous systems. We demonstrate that the decomposition of heat capacity based on partition function zeros allows the identification of transition-like crossovers originating from compact low-energy states, thereby enabling the evaluation of the foldability of HP sequences. The occurrence of significant crossovers between the collapse and folding transitions indicates slow folding behavior, whereas their absence characterizes good folders. This criterion is further validated through kinetic Monte Carlo simulations of two representative sequences. Full article

(This article belongs to the Section Polymer Physics and Theory)

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24 pages, 9097 KB

Open AccessReview

Functional Hydrogels in Food Applications: A Review of Crosslinking Technologies, Encapsulation Trends, and Emerging Challenges

by Sebastián Catalán Briones, Cassamo U. Mussagy, Fabiane O. Farias and Andrés Córdova

Polymers 2025, 17(21), 2955; https://doi.org/10.3390/polym17212955 - 6 Nov 2025

Viewed by 1105

Abstract

Hydrogels derived from natural and synthetic polymers have emerged as versatile materials with wide applications in food science, biotechnology, and health-related sectors, providing unique opportunities to encapsulate, protect, and deliver bioactive compounds, as well as to create new textures and functional properties in [...] Read more.

Hydrogels derived from natural and synthetic polymers have emerged as versatile materials with wide applications in food science, biotechnology, and health-related sectors, providing unique opportunities to encapsulate, protect, and deliver bioactive compounds, as well as to create new textures and functional properties in food systems. This review summarizes the latest advances in the design and application of hydrogels, highlighting the critical relationship between polymer structure, crosslinking strategies, and functional performance. The analysis reveals that while significant progress has been achieved, challenges persist in scaling laboratory-scale hydrogel systems to industrially relevant processes, where stability, reproducibility, and regulatory acceptance remain major bottlenecks. Emerging directions in the field include the development of smart hydrogels that respond to environmental stimuli (pH, temperature, or enzymatic activity), sustainable fabrication routes using renewable biopolymers, integration with advanced processing technologies such as 3D printing or microfluidics, and biorefinery approaches emphasizing their role in valorizing agro-industrial by-products into high-value functional materials. Hydrogels represent a promising platform at the interface of polymer science, food technology, and biotechnology, whose continued development will depend on multidisciplinary innovation aiming to meet consumer demands for sustainable, safe, and health-promoting food systems. Full article

(This article belongs to the Special Issue Applications of Biopolymer-Based Composites in Food Technology)

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24 pages, 4712 KB

Open AccessArticle

Bond Properties of Steel Bar in Polyoxymethylene-Fiber-Reinforced Coral Aggregate Concrete

by Zhuolin Xie, Lin Chen, Lepeng Huang, Junlong Jin, Jianmin Hua, Pow-Seng Yap and Yi Zhang

Polymers 2025, 17(21), 2954; https://doi.org/10.3390/polym17212954 - 6 Nov 2025

Viewed by 597

Abstract

The rapid expansion of island and reef infrastructure has intensified the demand for sustainable concrete materials, yet the scarcity of conventional aggregates and freshwater severely constrains their supply. More critically, the fundamental bonding mechanism between steel reinforcement and coral aggregate concrete (CAC) remains [...] Read more.

The rapid expansion of island and reef infrastructure has intensified the demand for sustainable concrete materials, yet the scarcity of conventional aggregates and freshwater severely constrains their supply. More critically, the fundamental bonding mechanism between steel reinforcement and coral aggregate concrete (CAC) remains poorly understood due to the highly porous, ion-rich nature of coral aggregates and the complex interfacial reactions at the steel–cement–coral interface. Moreover, the synergistic effect of polyoxymethylene (POM) fibers in modifying this interfacial behavior has not yet been systematically quantified. To fill this research gap, this study develops a C40-grade POM-fiber-reinforced CAC and investigates the composition–property relationship governing its bond performance with steel bars. A comprehensive series of pull-out tests was conducted to examine the effects of POM fiber dosage (0, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%), protective layer thickness (32, 48, and 67 mm), bar type, and anchorage length (2 d, 3 d, 5 d, and 6 d) on the interfacial bond behavior. Results reveal that a 0.6% POM fiber addition optimally enhanced the peak bond stress and restrained radial cracking, indicating a strong fiber-bridging contribution at the micro-interface. A constitutive bond–slip model incorporating the effects of fiber content and c/d ratio was established and experimentally validated. The findings elucidate the multiscale coupling mechanism among coral aggregate, POM fiber, and steel reinforcement, providing theoretical and practical guidance for the design of durable, low-carbon marine concrete structures. Full article

(This article belongs to the Special Issue Polymers in Civil Engineering)

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15 pages, 1938 KB

Open AccessArticle

Feasibility Study on Quantification of Biodegradable Polyester Microplastics Based on Intrinsic Fluorescence

by Tian-Chao Shi, Ze-Yang Zhang, Xiao-Han Zhou, Xing Zhang, Shao-Chuang Su, Hong Yang, Hao-Bo Chai, Ge-Xia Wang, Jun-Hui Ji, Yue Ding, Xu-Ran Liu and Dan Huang

Polymers 2025, 17(21), 2953; https://doi.org/10.3390/polym17212953 - 5 Nov 2025

Viewed by 515

Abstract

While biodegradable plastics alleviate plastic pollution, their degradation-derived biodegradable microplastics (BMPs) pose new ecological risks, necessitating efficient quantification methods. This study explores a label-free approach by leveraging the intrinsic fluorescence of common biodegradable polyesters (PLA, PHB, PBS, PBAT, PCL). We find that biodegradable [...] Read more.

While biodegradable plastics alleviate plastic pollution, their degradation-derived biodegradable microplastics (BMPs) pose new ecological risks, necessitating efficient quantification methods. This study explores a label-free approach by leveraging the intrinsic fluorescence of common biodegradable polyesters (PLA, PHB, PBS, PBAT, PCL). We find that biodegradable microplastics exhibit two types of characteristic fluorescence emission: one originating from molecular functional groups and the other originating from the chromophore formed by the aggregation of conjugated groups. Using PBAT as a model, we confirm that fluorescence intensity depends on the BMPs’ size and shape. Under 380 nm excitation, concentration-dependent signals are observed at 436 nm (indirectly from PBAT-enhanced water Raman scattering) and 465 nm (directly from PBAT intrinsic fluorescence), leading to successful linear models between BMPs’ mass concentration and fluorescence intensity over 100–500 mg/L, with correlation coefficients (R²) of 0.877 and 0.963, respectively. Compared with the fluorescence labeling method, the intrinsic fluorescence approach achieves comparable R² while exhibiting lower signal intensity (~10³). Nevertheless, its operational simplicity offers a distinct advantage for the rapid quantification of pre-isolated and purified microplastics. Full article

(This article belongs to the Special Issue Application and Degradation of Polymeric Materials in Agriculture)

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20 pages, 7443 KB

Open AccessArticle

Sweat-Resistant Parylene-C Encapsulated Conductive Textiles for Active Thermal Management

by Shi Hu, Dan Wang, Mohanapriya Venkataraman, Jiří Militký, Dana Křemenáková and Martin Palušák

Polymers 2025, 17(21), 2952; https://doi.org/10.3390/polym17212952 - 5 Nov 2025

Viewed by 663

Abstract

The development of electro-thermal textiles has attracted growing interest as a promising approach for active thermal management in wearable systems. Metallic-coated fabrics can efficiently generate heat through the Joule effect; however, their long-term performance and safety are severely limited under perspiration due to [...] Read more.

The development of electro-thermal textiles has attracted growing interest as a promising approach for active thermal management in wearable systems. Metallic-coated fabrics can efficiently generate heat through the Joule effect; however, their long-term performance and safety are severely limited under perspiration due to metal ion release and corrosion. To overcome these challenges, this study introduces a Parylene-C encapsulation strategy for copper-coated polyethylene terephthalate nonwovens (CuPET) using a chemical vapor deposition (CVD) process. The conformal, biocompatible Parylene-C films (thickness 4–16 μm) act as effective protective barriers while preserving the porous textile structure. Morphological and comfort analyses demonstrate a controlled reduction in air permeability from 3100 to 1100 L·m⁻²·s⁻¹, maintaining acceptable breathability. Electro-thermal measurements reveal rapid and uniform heating, reaching 40–45 °C within 2 min at 2 V, and the addition of a thermal insulation layer further enhances the Joule heating efficiency, increasing the steady-state temperature by approximately 6 °C. ICP–OES results show an ≈80% reduction in copper ion release (from 28.34 mg·L⁻¹ to 5.80 mg·L⁻¹) after artificial sweat exposure. This work demonstrates a scalable encapsulation route that effectively balances sweat protection, electrical stability, and thermal performance, paving the way for safe, durable, and actively heated smart textiles for advanced thermal insulation applications. Full article

(This article belongs to the Special Issue Advanced Study on Polymer-Based Textiles)

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17 pages, 3529 KB

Open AccessArticle

Achieving High-Performance Polypropylene-Based Synthetic Paper with High-Modulus Organic Oligomer and Biaxial Stretching Force Field

by Zhenkun Wang, Quanjia Du, Weiyouran Hong, Guiying Yu, Haoran Wang, Yanshan Feng, Xinyu Chen, Hongrun Li, Shaoyun Guo and Chunhai Li

Polymers 2025, 17(21), 2951; https://doi.org/10.3390/polym17212951 - 5 Nov 2025

Viewed by 496

Abstract

The widespread replacement of cellulose paper with polypropylene (PP)-based synthetic paper has been hindered by the relatively low stiffness and modulus of PP. Conventional approaches that incorporate rigid inorganic fillers can enhance the modulus but typically compromise processability and mechanical performance. In this [...] Read more.

The widespread replacement of cellulose paper with polypropylene (PP)-based synthetic paper has been hindered by the relatively low stiffness and modulus of PP. Conventional approaches that incorporate rigid inorganic fillers can enhance the modulus but typically compromise processability and mechanical performance. In this work, we propose a dual strategy by introducing high-modulus organic hydrogenated resin fillers (C9) and applying a biaxial stretching force field. The biaxial stretching process not only promotes PP crystallization but also significantly improves the uniform dispersion of C9 fillers. As a result, a composite paper with ultrafine C9 dispersion and a crystalline self-reinforced structure was successfully fabricated. The composite exhibits a modulus that is 38% higher than that of biaxially stretched neat PP and 218% higher than that of unstretched neat PP. Furthermore, under biaxial stretching, the C9 fillers impart a toughening effect, effectively overcoming the conventional stiffness–toughness trade-off. This work therefore provides a promising strategy for the scalable fabrication of high-performance PP-based synthetic paper. Full article

(This article belongs to the Special Issue Advanced Polymer Composites: Structure and Mechanical Properties)

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18 pages, 3913 KB

Open AccessArticle

Preparation and Characterization of Bioplastics Based on Sweet Potato Peel Starch, Aloe vera and Eucalyptus Oil

by Mercedes Puca-Pacheco, María Guadalupe Neira-Velázquez, Gonzalo Canché-Escamilla, Melanie Ascue-Caballero, Alvaro Adrian Girao-Sánchez and César Augusto Tacuri-Puca

Polymers 2025, 17(21), 2950; https://doi.org/10.3390/polym17212950 - 5 Nov 2025

Viewed by 1139

Abstract

The aim of this study was to produce and characterize bioplastics derived from sweet potato peel starch, Aloe vera gel, and eucalyptus essential oil. Starch from sweet potato peels was extracted using a wet method, yielding 3.54%, while eucalyptus oil was obtained via [...] Read more.

The aim of this study was to produce and characterize bioplastics derived from sweet potato peel starch, Aloe vera gel, and eucalyptus essential oil. Starch from sweet potato peels was extracted using a wet method, yielding 3.54%, while eucalyptus oil was obtained via steam distillation, with a yield of 1.4%. In order to assess the influence of Aloe vera and eucalyptus oil concentrations on the properties of bioplastics, a 2^2 factorial design was implemented. Consequently, bioplastic films were produced using the casting technique. As a result, the films appeared brown, translucent, and homogeneous, while also exhibiting a rough surface texture. Mechanical testing revealed that the films possessed a high Young’s modulus of 41.1 ± 11.1 MPa, a maximum tensile strength of 2.1 ± 0.4 MPa, and an elongation at break of 21.6 ± 4.3%. These properties were achieved with a formulation containing 70% w/w Aloe vera, 0.6% w/w eucalyptus oil, and 5% w/w sweet potato peel starch, suggesting a promising eco-friendly alternative to conventional plastics for potential use in packaging applications. Full article

(This article belongs to the Special Issue Bioplastics)

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18 pages, 2232 KB

Open AccessArticle

Additive Manufacturing to Mimic the Nonlinear Mechanical Behavior of Cardiac Soft Tissue

by Sara Valvez, M. Oliveira-Santos, L. Gonçalves, A. P. Piedade and A. M. Amaro

Polymers 2025, 17(21), 2949; https://doi.org/10.3390/polym17212949 - 5 Nov 2025

Viewed by 564

Abstract

Soft biological tissues display highly nonlinear and anisotropic mechanical behavior, which is critical to their physiological function. Replicating these mechanical properties using engineered materials and additive manufacturing represents a significant challenge in biomedical engineering, particularly for surgical simulation, device development, and preclinical testing. [...] Read more.

Soft biological tissues display highly nonlinear and anisotropic mechanical behavior, which is critical to their physiological function. Replicating these mechanical properties using engineered materials and additive manufacturing represents a significant challenge in biomedical engineering, particularly for surgical simulation, device development, and preclinical testing. The left atrial appendage (LAA) was selected since it plays a central role in thrombus formation during atrial fibrillation, significantly contributing to cardioembolic stroke. This study proposes a framework for reproducing the nonlinear stress–strain behavior of soft tissue using 3D-printed models. The methodology integrates experimental material selection with optimization of key printing parameters to ensure structural reliability and functional mechanical performance. Two polymers—polyurethane (TPU) and a thermoplastic with elastomer-type behavior (TPE)—were selected for their tunable hardness and elasticity. A parametric study was conducted to investigate the effects of Shore A hardness (60A to 100A), infill density (0% to 100%), and external shell number (zero to two) on the tensile performance of printed models. Mechanical testing was performed to extract stress–strain curves and evaluate the mechanical response. The practical implications of this study are significant, demonstrating the potential of additive manufacturing for anatomical reproduction and replicating functional mechanical properties in soft tissue models. Full article

(This article belongs to the Special Issue Mechanical Behavior of Polymeric Materials: Recent Studies, 2nd Edition)

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18 pages, 10615 KB

Open AccessReview

Acoustic Emission Mechanisms During Polymer Processing and Chain Orientation: From Amorphous to Crystalline

by Guowei Chen and Tizazu Mekonnen

Polymers 2025, 17(21), 2948; https://doi.org/10.3390/polym17212948 - 5 Nov 2025

Viewed by 646

Abstract

Acoustic emission (AE) technology has emerged as a highly sensitive and non-destructive method for the real-time monitoring of defect formation and microstructural changes during the manufacturing and early service life of polymeric materials and composites. This review highlights the fundamental principles and applications [...] Read more.

Acoustic emission (AE) technology has emerged as a highly sensitive and non-destructive method for the real-time monitoring of defect formation and microstructural changes during the manufacturing and early service life of polymeric materials and composites. This review highlights the fundamental principles and applications of AE in detecting crystallization-induced defects, such as cavities, dislocations, and microcracks, as well as plastic deformation mechanisms, including chain orientation, cavitation, and stress release. It is shown that AE activity correlates strongly with crystallinity and processing conditions, providing critical insights into microstructure–property relationships. The possible mechanisms can be the friction between grain boundaries, the local stress release, chain movement, phase changing, and fiber/filler debonding, among others. A comprehensive understanding can help with the prediction/prevention of early defects in the crystalline polymer processing. Furthermore, integrating AE with artificial intelligence and multi-sensor data fusion offers promising pathways toward smart, adaptive manufacturing systems capable of real-time quality control and early defect diagnosis in high-performance polymer composites. Full article

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

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21 pages, 4394 KB

Open AccessArticle

Experimental Investigation of Nanodiamond Reinforcement in PU for Enhancing Mechanical, Scratch, Rheological, Thermal, and Shape-Memory Properties

by Markapudi Bhanu Prasad, Nashmi H. Alrasheedi, P. S. Rama Sreekanth, Borhen Louhichi, Santosh Kumar Sahu and Nitesh Dhar Badgayan

Polymers 2025, 17(21), 2947; https://doi.org/10.3390/polym17212947 - 4 Nov 2025

Viewed by 693

Abstract

Shape-memory polymers (SMPs) are a unique class of smart materials capable of recovering their original shape upon external stimuli, with thermoresponsive polyurethane (PU) being one of the most widely studied systems. However, the relatively low mechanical strength, thermal stability, and durability of PU [...] Read more.

Shape-memory polymers (SMPs) are a unique class of smart materials capable of recovering their original shape upon external stimuli, with thermoresponsive polyurethane (PU) being one of the most widely studied systems. However, the relatively low mechanical strength, thermal stability, and durability of PU limit its broader functional applications. PU/ND composites containing 0.1–0.5 wt.% ND were fabricated via melt blending and injection molding method. The objective was to evaluate the effect of ND reinforcement on the mechanical, scratch, thermal, rheological, and shape-memory properties. Results show that tensile strength increased up to 114% and Young’s modulus by 11% at 0.5 wt.% ND, while elongation at break decreased due to restricted chain mobility. Hardness improved by 21%, and scratch resistance was significantly enhanced, with the coefficient of friction reduced by 56% at low loads. Thermal stability was improved, with the maximum degradation temperature shifting from 350 °C (pure PU) to 362 °C (0.5 wt.% PU/ND) and char yield increasing by 34%. DSC revealed an increase in glass transition temperature from 65 °C to 68.6 °C. Rheological analysis showed an 89% reduction in damping factor (tan δ), indicating enhanced elasticity. Shape-memory tests confirmed notable improvements in both shape fixity and recovery ratios across successive cycles compared to neat PU, with the highest enhancements observed for the 0.5 wt.% PU/ND nanocomposite—showing up to 7.6% higher fixity and 32% higher recovery than pure PU. These results demonstrate that ND reinforcement effectively strengthens PU while preserving and improving its shape-memory behavior, making the composites promising candidates for high-performance smart materials in sensors, actuators, and aerospace applications. Full article

(This article belongs to the Special Issue Polyurethane Composites: Properties and Applications)

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35 pages, 3549 KB

Open AccessReview

Multimatrix Composite Materials for Rocket Nozzle Manufacturing: A Comparative Review

by Mohammed Meiirbekov, Mukhammed Sadykov, Assem Kuandyk, Marat Nurguzhin, Marat Janikeyev, Partizan Gulmaira, Laura Mustafa and Nurmakhan Yesbolov

Polymers 2025, 17(21), 2946; https://doi.org/10.3390/polym17212946 - 4 Nov 2025

Viewed by 1052

Abstract

Rocket engine nozzle blocks operate under extreme thermal and oxidative loads, requiring materials with high temperature resistance, dimensional stability, and a predictable lifetime without active cooling. This review provides a comparative overview of multimatrix composite materials-including C/C, C/SiC, SiC/SiC, MMC, and polymer-based ablative [...] Read more.

Rocket engine nozzle blocks operate under extreme thermal and oxidative loads, requiring materials with high temperature resistance, dimensional stability, and a predictable lifetime without active cooling. This review provides a comparative overview of multimatrix composite materials-including C/C, C/SiC, SiC/SiC, MMC, and polymer-based ablative systems-representing the full spectrum of materials used in non-cooled rocket nozzles. The study highlights the evolutionary continuum from polymeric ablative systems to carbon, ceramic, and metallic matrices, demonstrating how each class extends operational limits in temperature capability, reusability, and structural integrity. Polymer and ablative composites serve as the foundation of thermal protection through controlled ablation and insulation, while carbon- and ceramic-based systems ensure long-term performance at ultra-high temperatures (>1600 °C). MMCs bridge these classes by combining strength, impact toughness, and thermal conductivity in transition zones. Particular attention is given to manufacturing technologies such as PIP, CVI, LPI, RS, powder metallurgy, casting, diffusion bonding, and filament winding, emphasizing their effect on microstructure, porosity, and lifetime. A practical selection matrix linking nozzle zones, mission profiles, and composite types is proposed, outlining trade-offs among performance, mass, lifetime, and manufacturability, and guiding the design of next-generation thermal protection and propulsion systems based on the multimatrix concept. Full article

(This article belongs to the Special Issue Polymer Composites: Design, Manufacture and Characterization)

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13 pages, 1561 KB

Open AccessArticle

Hydroelectricity Generation from Fiber-Oriented Waste Paper via Capillary-Driven Charge Separation

by Hyun-Woo Lee, Seung-Hwan Lee, So Hyun Baek, Yongbum Kwon, Mi Hye Lee, Kanghyuk Lee, Inhee Cho, Bum Sung Kim, Haejin Hwang and Da-Woon Jeong

Polymers 2025, 17(21), 2945; https://doi.org/10.3390/polym17212945 - 4 Nov 2025

Viewed by 454

Abstract

Hydroelectricity energy harvesting has emerged as a promising, eco-friendly alternative for addressing the growing demand for sustainable energy solutions. In this study, we present a hydroelectricity energy harvester fabricated from shredded waste printing paper (WPP), offering a novel waste-to-energy conversion strategy that requires [...] Read more.

Hydroelectricity energy harvesting has emerged as a promising, eco-friendly alternative for addressing the growing demand for sustainable energy solutions. In this study, we present a hydroelectricity energy harvester fabricated from shredded waste printing paper (WPP), offering a novel waste-to-energy conversion strategy that requires neither material purification nor complex processing. The device leverages the randomly entangled fiber network of WPP to facilitate capillary-driven moisture diffusion and electric double layer (EDL) formation, thereby enabling efficient electrokinetic energy conversion. The random arrangement of WPP fibers increases the effective EDL area, allowing the waste printing paper generator (WPPG) to achieve an open-circuit voltage of 0.372 V and a short-circuit current of 135 μA at room temperature under optimized electrolyte conditions. This study demonstrates that carbon-black-coated WPP can be effectively upcycled into a high-performance hydroelectricity generator, exhibiting excellent electrical output at ambient conditions. By combining material recycling with efficient energy conversion, this system establishes a practical and sustainable pathway for distributed power generation. Overall, this work not only presents an environmentally responsible approach to device fabrication but also highlights that hydroelectricity energy harvesting using WPPG represents a promising alternative energy route for future applications. Full article

(This article belongs to the Special Issue Polymer-Based Advances in Energy Harvesting Technologies and Applications)

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31 pages, 11474 KB

Open AccessArticle

Tribological Performance of Glass/Kevlar Hybrid Epoxy Composites: Effects of Pressurized Water-Immersion Aging Under Reciprocating Sliding Wear

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

Polymers 2025, 17(21), 2944; https://doi.org/10.3390/polym17212944 - 4 Nov 2025

Viewed by 444

Abstract

This study quantifies how pressurized water immersion alters the reciprocating sliding behavior of glass and Kevlar woven fabric-reinforced polymer hybrid composite laminates. Specimens were immersed in deionized water at 10 bar and 25 °C for 0, 7, 14, and 21 days, then tested [...] Read more.

This study quantifies how pressurized water immersion alters the reciprocating sliding behavior of glass and Kevlar woven fabric-reinforced polymer hybrid composite laminates. Specimens were immersed in deionized water at 10 bar and 25 °C for 0, 7, 14, and 21 days, then tested against a 6 mm 100Cr6 steel ball at 20 N under four regimes that combine 1 or 2 Hz with 10 m or 20 m total sliding. Water uptake rose from 0 to 8.54% by day 21 and followed a short-time Fickian square root of time trend, indicating diffusion-controlled sorption. The coefficient of friction exhibited a robust nonmonotonic response with a pronounced minimum at 14 days that was typically 20 to 40% lower than the unaged reference across frequencies and distances, while 7 days produced a partial decrease and 21 days trended upward. Three-dimensional profilometry showed progressive widening and deepening of wear tracks with immersion, for example, at 1 Hz and 10 m width increased from about 1596 to about 2050 to 2101 μm and depth from about 128 to about 184 to 185 μm, with a transient narrowing at 2 Hz after 7 days. Scanning electron microscopy corroborated a transition from mild plowing to matrix plasticization with fiber–matrix debonding and debris compaction. Beyond geometric wear metrics, this study re-processed the existing profilometry and COF records to derive a moisture-dependent mechanistic approach. Moisture uptake up to 8.54% reorganizes the third body at the interface so that friction drops markedly at 14 days (typically 20–40% below the unaged state), while concurrent matrix plasticization and interface weakening enlarge the wear cross-section extracted from the same 3D maps, decoupling friction from damage width/depth under wet conditioning. Factorial analysis ranked immersion time as the dominant driver of damage for width and depth with frequency as a secondary factor and sliding distance as a minor factor, highlighting immersion-controlled tribological design windows for marine and humid service. Full article

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

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17 pages, 3441 KB

Open AccessArticle

Enhancing Fire Resistance and Mechanical Properties of Wood Strand Boards by Impregnation with Sodium Bicarbonate and Sodium Borate

by Roger Pedieu, Aziz Bentis, Bernard Riedl, Xiang-Ming Wang, James Deng, Flavia Lega Braghiroli and Ahmed Koubaa

Polymers 2025, 17(21), 2943; https://doi.org/10.3390/polym17212943 - 4 Nov 2025

Viewed by 709

Abstract

The development of halogen-free flame-retardant formulations for wood-based panels is a promising strategy to improve both fire safety and environmental performance. In this study, oriented strand boards (OSB) were impregnated with aqueous solutions of sodium borate (SBo) and sodium bicarbonate (SBi) to evaluate [...] Read more.

The development of halogen-free flame-retardant formulations for wood-based panels is a promising strategy to improve both fire safety and environmental performance. In this study, oriented strand boards (OSB) were impregnated with aqueous solutions of sodium borate (SBo) and sodium bicarbonate (SBi) to evaluate their combined effects on fire resistance and mechanical properties. Fire performance was assessed using the ASTM D3806 small-scale tunnel test, while mechanical and physical properties were measured according to ASTM D1037. Significant improvements in fire performance were observed: mass loss (ML) during flammability testing decreased by 38% (from 6.9% to 4.3%), flame spread speed (FSS) was reduced by more than 50% (from 6.8 to 3.3 mm/s), and after-flame times (AFT) dropped from 17.2 s to 0 s. Thermogravimetric analysis (TGA) further confirmed enhanced thermal stability, with increased char residue (from 16.9% in untreated boards to 31.5% in treated ones). Mechanical testing revealed a 16% increase in internal bond (IB) strength (from 0.44 to 0.51 MPa), while modulus of rupture (MOR) and modulus of elasticity (MOE) were only slightly affected (decreased by up to 4.2% and 3.6%, respectively). Interestingly, the two additives exerted contrasting effects: SBo reduced strength and bonding performance, whereas SBi improved internal bond strength and dimensional stability. The optimal balance was obtained with treatment P250-50 (250 g SBi and 50 g SBo), which combined enhanced fire resistance with acceptable mechanical integrity. Overall, the results demonstrate that the synergistic use of SBo and SBi offers an effective halogen-free approach to simultaneously enhance the fire resistance and mechanical performance of OSB panels, highlighting its potential for industrial applications. Full article

(This article belongs to the Special Issue Flame-Retardant Polymer Composites II)

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17 pages, 4264 KB

Open AccessArticle

Reduction in Sulfur Diffusion in Recycled Ground Rubber-Containing Compounds to Improve Tensile Strength

by Stefan Frosch, Volker Herrmann, Fabian Grunert and Anke Blume

Polymers 2025, 17(21), 2942; https://doi.org/10.3390/polym17212942 - 3 Nov 2025

Viewed by 580

Abstract

Recycling end-of-life rubber to compound components for new formulations is one of the most promising ways to reach the sustainability goals of the rubber industry. Today, devulcanization and pyrolysis are both methods to reuse crosslinked elastomers. A third recycling approach is to process [...] Read more.

Recycling end-of-life rubber to compound components for new formulations is one of the most promising ways to reach the sustainability goals of the rubber industry. Today, devulcanization and pyrolysis are both methods to reuse crosslinked elastomers. A third recycling approach is to process end-of-life rubber into ground rubber (GR), which is then added to green compounds. However, free sulfur diffuses during mixing, storage and vulcanization from the matrix material into the GR particles. As a result, the crosslink density in the matrix is reduced, which deteriorates the in-rubber properties of GR-containing vulcanizates compared to those that do not contain GR. Therefore, GR particles are mainly used today for rubber parts with less demanding dynamic-mechanical requirements, which limits the use of the particles. This study presents an approach for reducing the sulfur diffusion from the matrix into the GR particles by prevulcanizing the green matrix material. This leads to GR-containing vulcanizates with significantly improved mechanical properties. This new approach shows that the quality of the recycled rubber product can be significantly increased by blocking the sulfur diffusion. Even though such prevulcanization is currently only feasible under laboratory conditions, it might also pave the way for finding solutions in a production scale for an effective incorporation of GR into new rubber compounds. Full article

(This article belongs to the Special Issue Exploration and Innovation in Sustainable Rubber Performance)

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27 pages, 5305 KB

Open AccessReview

Flexible Intelligence on a Green Skeleton: Progress and Challenges of CNF-Enabled Multimodal Sensing Platforms

by Hemiao Wang, Guanlin Huo, Guijuan Xu, Dehai Yu, Shanshan Liu and Qiang Wang

Polymers 2025, 17(21), 2941; https://doi.org/10.3390/polym17212941 - 3 Nov 2025

Viewed by 447

Abstract

Cellulose nanofibrils (CNFs) provide a green scaffold for next-generation flexible sensors. They unite abundance, mechanical robustness, biocompatibility, and an easily engineered surface. This review synthesizes advances from the past five years in low-carbon CNF manufacturing. We cover biomass pretreatment, high-solid mechanical fibrillation, and [...] Read more.

Cellulose nanofibrils (CNFs) provide a green scaffold for next-generation flexible sensors. They unite abundance, mechanical robustness, biocompatibility, and an easily engineered surface. This review synthesizes advances from the past five years in low-carbon CNF manufacturing. We cover biomass pretreatment, high-solid mechanical fibrillation, and in situ functionalization. We then elucidate mechanisms that govern CNF films, aerogels, and double-network hydrogels used across humidity, temperature, strain/pressure, optical, electrochemical, and biosensing platforms. Particular attention is given to multiscale conductive networks, surface-charge regulation, and reversible dynamic crosslinking. Together, these motifs raise sensitivity, widen the linear response windows, and strengthen environmental tolerance. We interrogate bottlenecks that impede scale-up, including energy demand, batch-to-batch variability, and device-level integration. We also assess prospects for deep-eutectic-solvent recycling, roll-to-roll digital printing, and algorithm-guided structural design. Finally, we outline directions for self-healing and self-powered biomimetic architectures, fully degradable life-cycle design, and integrated “sense–store–compute” nodes. These analyses chart a credible path from laboratory discovery to industrial deployment of CNF-based sensing technologies. Full article

(This article belongs to the Special Issue Advanced Polymers for Biosensor Applications)

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21 pages, 4583 KB

Open AccessArticle

Investigation of the Mechanical and Optical Properties of ABS Plus Materials in Different Colors After Aging

by Muhammet Akyol, Nergizhan Anaç, Oğuz Koçar, Erhan Baysal and İrfan Akgül

Polymers 2025, 17(21), 2940; https://doi.org/10.3390/polym17212940 - 3 Nov 2025

Viewed by 650

Abstract

As the global 3D printing market continues to grow, the consumption of plastic products produced by 3D printers is also increasing. The role of 3D-printed products in both daily use and industrial applications has been progressively reinforced. Plastic materials undergo physical and chemical [...] Read more.

As the global 3D printing market continues to grow, the consumption of plastic products produced by 3D printers is also increasing. The role of 3D-printed products in both daily use and industrial applications has been progressively reinforced. Plastic materials undergo physical and chemical changes when exposed to environmental conditions such as temperature, light, and humidity. Consequently, they are subjected to aging during use, which shortens their service life. With the expanding use of 3D printing technology in various sectors such as healthcare, automotive, aerospace, and defense, it has become increasingly important to understand the changes (potential decreases or losses) in the performance of these materials after long-term exposure to environmental conditions. This study aims to contribute to the understanding of potential changes in 3D-printed ABS Plus material by examining the phenomenon of aging induced by exposure to radiation from a xenon arc lamp. ABS Plus samples of different colors (yellow, purple, red, green, and blue) were subjected to aging for 0, 112, 225, 337, and 450 h using a xenon arc lamp. To investigate the effects of aging, the mechanical (tensile, flexural, and hardness) and optical (color and gloss variations) properties of the samples were compared before and after aging. Following the mechanical tests, the fracture modes of the specimens were also examined. In addition, Scanning Electron Microscope (SEM) images were obtained to further discuss the effects of aging. The results revealed that the mechanical properties of the reference samples varied depending on color. The highest tensile strength was observed in the yellow samples (33.46 MPa), while the highest flexural strength was recorded in the green samples (58.46 MPa). After aging, the lowest tensile strength was found in the purple samples aged for 337 h (24.63 MPa), whereas the lowest bending force was measured in the red samples aged for 450 h (45.27 N). Overall, the mechanical properties of the samples varied with aging duration, with the blue and green specimens being the least affected. For the blue specimens, after 112, 225, and 337 h of aging, an increase in tensile strength was observed (2.77%, 10.54%, and 9.58%, respectively), while a decrease occurred after 450 h of aging (−6.22%). For the green specimens, after 112, 225, and 337 h of aging, the tensile strength remained similar to that of the reference sample (−2.97%, 0.23%, and 0.05%, respectively) but decreased after 445 h of aging (−8.09%). In terms of optical properties, the most significant color change (−23.51) was observed in the purple samples. Gloss measurements indicated that the impact of aging increased with exposure time. Full article

(This article belongs to the Section Polymer Processing and Engineering)

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19 pages, 3819 KB

Open AccessArticle

Research on the Physical Properties and Internal Structure of PVP/Nb₂O₅ Nanocomposite Coatings

by Paweł Jarka, Pallavi Kumari, Małgorzata Łazarska, Marcin Godzierz, Sonia Kotowicz, Marek Marcisz, Marcelina Bochenek, Łucja Hajduk, Magdalena M. Szindler and Barbara Hajduk

Polymers 2025, 17(21), 2939; https://doi.org/10.3390/polym17212939 - 3 Nov 2025

Viewed by 801

Abstract

The subject of this study is the effects of various concentrations of niobium pentoxide nanoparticles (Nb₂O₅ NPs) on the physical, optical, and thermal properties of thin films of poly(N-vinylpyrrolidone) (PVP). The obtained results indicate that the addition of nanoparticles significantly [...] Read more.

The subject of this study is the effects of various concentrations of niobium pentoxide nanoparticles (Nb₂O₅ NPs) on the physical, optical, and thermal properties of thin films of poly(N-vinylpyrrolidone) (PVP). The obtained results indicate that the addition of nanoparticles significantly affects the physical properties of the investigated materials, limiting their optical UV transmittance in the range of 300–500 nm by approximately 20–40% and increasing the material’s resistance to moisture that is present in the surrounding environment. Based on the thermal measurements performed using differential scanning calorimetry (DSC) and variable temperature spectroscopic ellipsometry (VASE), two distinct glass transition temperatures T_g for pure PVP and its Nb₂O₅ composites were revealed, with an additional intermediate T_g appearing in the composites, varying in the range of 135–168 °C (ellipsometric temperature cycle). This intermediate transition indicates the formation of an interfacial region with modified polymer chain mobility due to the interactions occurring between Nb₂O₅ nanoparticles and the PVP matrix. The results obtained from the scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and detailed Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) analyses also confirmed the presence of this interfacial area and indicated that it arises from nanoparticle agglomeration and surface cluster formation. The contact angle measurements revealed that the composites containing 15% and 25% Nb₂O₅ exhibited greater hydrophobicity. These results suggest that the investigated composite coatings could be employed as surface coverings to protect against external, environmental influences, such as moisture and UV radiation. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Nanocomposite Films and Coatings)

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20 pages, 4491 KB

Open AccessArticle

Experimental Study on the Effect of Humidity on the Mechanical Properties of 3D-Printed Mechanical Metamaterials

by Qian Sun, Xiaojun Tan, Jianhao Man, Shuai Li, Zeeshan Ali, Kaiyang Yin, Bo Cao and Christoph Eberl

Polymers 2025, 17(21), 2938; https://doi.org/10.3390/polym17212938 - 3 Nov 2025

Viewed by 951

Abstract

In this study, six common fused filament fabrication (FFF) polymers—PEEK, PLA, PETG, ABS, Nylon, and TPU—were acclimatized at 15%, 45%, and 95% relative humidity (RH) to characterize tensile behavior, including Young’s modulus, maximum strain, and ultimate tensile strength. Separately, mechanical metamaterial samples at [...] Read more.

In this study, six common fused filament fabrication (FFF) polymers—PEEK, PLA, PETG, ABS, Nylon, and TPU—were acclimatized at 15%, 45%, and 95% relative humidity (RH) to characterize tensile behavior, including Young’s modulus, maximum strain, and ultimate tensile strength. Separately, mechanical metamaterial samples at relative densities (RD) of 25%, 35%, and 45% were tested in compression at the same RH levels to evaluate stiffness, strength, and Poisson’s ratio. The water absorption process can generally be divided into different stages—rapid uptake (0–12 h), a plateau (12–60 h), and a late rebound (60–100 h)—with a total uptake ranking of Nylon > PETG > PLA ≈ ABS > TPU ≈ PEEK. Samples under tensile and compressive tests show a great difference between properties at different RD and RH levels. Poisson’s ratio indicates that material responses remain predictable at low-to-moderate RH, whereas high RH serves as a critical threshold inducing abrupt Poisson’s ratio behavioral shifts. This study provides systematic validation for the application of 3D-printed metamaterials under varying humidity conditions, such as biomedical implants in human body. Full article

(This article belongs to the Special Issue Smart Polymers and Mechanical Metamaterials)

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21 pages, 64275 KB

Open AccessArticle

Characterization on Mode-I/II Interlaminar Strength and Fracture Toughness of Co-Cured Fiber–Metal Laminates

by Mingjie Wang, Hongyi Hao, Qinghao Liu, Xinyue Miao, Ziye Lai, Tianqi Yuan, Guohua Zhu and Zhen Wang

Polymers 2025, 17(21), 2937; https://doi.org/10.3390/polym17212937 - 2 Nov 2025

Viewed by 725

Abstract

This study systematically evaluates the mode-I (opening) and mode-II (shearing) interlaminar strength and fracture toughness of four co-cured fiber–metal laminates (FMLs): AL–CF (aluminum–carbon fiber fabric), AL–GF (aluminum–glass fiber fabric), AL–HC (aluminum–carbon/glass hybrid fabric), and AL–HG (aluminum–glass/carbon hybrid fabric). Epoxy adhesive films were interleaved [...] Read more.

This study systematically evaluates the mode-I (opening) and mode-II (shearing) interlaminar strength and fracture toughness of four co-cured fiber–metal laminates (FMLs): AL–CF (aluminum–carbon fiber fabric), AL–GF (aluminum–glass fiber fabric), AL–HC (aluminum–carbon/glass hybrid fabric), and AL–HG (aluminum–glass/carbon hybrid fabric). Epoxy adhesive films were interleaved between metal and composite plies to enhance interfacial bonding. Mode-I interlaminar tensile strength (ILTS) and mode-II interlaminar shear strength (ILSS) were measured using curved beam and short beam tests, respectively, while mode-I and mode-II fracture toughness (

G_{I c}

and

G_{I I c}

) were obtained from double cantilever beam (DCB) and end-notched flexure (ENF) tests. Across laminates, interlaminar tensile strength (ILTS) values lie in a narrow band of 31.6–31.8 MPa and interlaminar shear strength (ILSS) values in 41.0–41.9 MPa. The mode-I initiation (

G_{I c, i n i t}

) and propagation (

G_{I c, p r o p}

) toughnesses are 0.44–0.56 kJ/m² and 0.54–0.64 kJ/m², respectively, and the mode-II toughness (

G_{I I c}

) is 0.65–0.79 kJ/m². Scanning electron microscopy reveals that interlaminar failure localizes predominantly at the metal–adhesive interface, displaying river-line features under mode-I and hackle patterns under mode-II, whereas the adhesive–composite interface remains intact. Collectively, the results indicate that, under the present processing and test conditions, interlaminar strength and toughness are governed by the metal–adhesive interface rather than the composite reinforcement type, providing a consistent strength–toughness baseline for model calibration and interfacial design. Full article

(This article belongs to the Special Issue Advanced Fiber-Reinforced Polymer Composites: Design, Manufacturing, Characterization, and Application)

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10 pages, 3491 KB

Open AccessArticle

Prestrain-Enabled Stretchable and Conductive Aerogel Fibers

by Hao Yin and Jian Zhou

Polymers 2025, 17(21), 2936; https://doi.org/10.3390/polym17212936 - 1 Nov 2025

Viewed by 724

Abstract

Aerogels combine ultralow density with high surface area, yet their brittle, open networks preclude tensile deformation and hinder integration into wearable electronics. Here we introduce a prestrain-enabled coaxial architecture that converts a brittle conductive aerogel into a highly stretchable fiber. A porous thermoplastic [...] Read more.

Aerogels combine ultralow density with high surface area, yet their brittle, open networks preclude tensile deformation and hinder integration into wearable electronics. Here we introduce a prestrain-enabled coaxial architecture that converts a brittle conductive aerogel into a highly stretchable fiber. A porous thermoplastic elastomer (TPE) hollow sheath is wet-spun using a sacrificial lignin template to ensure solvent exchange and robust encapsulation. Conductive polymer-based precursor dispersions are infused into prestretched TPE tubes, frozen, and lyophilized; releasing the prestretch then programs a buckled aerogel core that unfolds during elongation without catastrophic fracture. The resulting TPE-wrapped aerogel fibers exhibit reversible elongation up to 250% while retaining electrical function. At low strains (<60%), resistance changes are small and stable (ΔR/R₀ < 0.04); at larger strains the response remains monotonic and fully recoverable, enabling broad-range sensing. The mechanism is captured by a strain-dependent percolation model in which elastic decompression, contact sliding, and controlled fragmentation/reconnection of the aerogel network govern the signal. This generalizable strategy decouples elasticity from conductivity, establishing a scalable route to ultralight, encapsulated, and skin-compatible aerogel fibers for smart textiles and deformable electronics. Full article

(This article belongs to the Special Issue Advances in Polymers-Based Functional and Smart Textiles)

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Polymers, Volume 17, Issue 21 (November-1 2025) – 157 articles

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