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Polymers
Volume 17
Issue 5
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Polymers, Volume 17, Issue 5 (March-1 2025) – 152 articles

Cover Story (view full-size image): The polymer industry has embraced the move towards sustainability to reduce dependency on fossil fuels. The use of renewable feedstocks, such as lignin, has been shown to be a promising alternative to fossil fuels. In this study, biobased organic diols derived from phenolic aldehyde by-products in the depolymerization of lignin for the synthesis of polyesters and polyurethanes are described, including the preparation of polyester polyols and polyurethane foams. View this paper
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12 pages, 15543 KiB  
Article
Enhancing the Fatigue Properties of Rigid Polyurethane Foam by Dissipating the Mechanical Energy of Rubber Powder
by Jinlong Ju, Nana Yang, Yifei Zhang, Lei Yu, Guolu Ma and Wenhua Wu
Polymers 2025, 17(5), 705; https://doi.org/10.3390/polym17050705 - 6 Mar 2025
Viewed by 629
Abstract
Rigid polyurethane-based foam is an ideal choice for sandwich-panel-filling materials due to its high strength, low thermal conductivity, high adhesion, and high chemical resistivity. Since sandwich panel materials often face cyclic mechanical loads during their service, it is significant to study the design [...] Read more.
Rigid polyurethane-based foam is an ideal choice for sandwich-panel-filling materials due to its high strength, low thermal conductivity, high adhesion, and high chemical resistivity. Since sandwich panel materials often face cyclic mechanical loads during their service, it is significant to study the design methods of fatigue-resistant rigid polyurethane foam and its fatigue failure mechanism to improve the performance of sandwich-panel-filling materials. In this study, a fatigue-resistant rubber powder/polyurethane composite material was prepared by introducing rubber powder, and its fatigue failure mechanism was systematically studied. The static mechanical test results indicate that with the introduction of 20% rubber powder, the compressive strength (at 85% strain) increased to 588 kPa. Additionally, thanks to the excellent energy absorption and dissipation properties of rubber powder, it can effectively dissipate mechanical energy during cyclic loading. The fatigue test results show that after the introduction of rubber powder, the fatigue life of the polyurethane foam material increases from 10,258 cycles (for PU, stress ratio 0.6) to 45,987 cycles (for 20R-PU, stress ratio 0.6). This study not only proves the fact that rubber powder can improve the fatigue performance of foam materials but also provides a potential option for the design of high-performance filling materials. Full article
(This article belongs to the Section Polymer Physics and Theory)
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19 pages, 5025 KiB  
Article
Investigations on Thermal Transitions in PDPP4T/PCPDTBT/AuNPs Composite Films Using Variable Temperature Ellipsometry
by Paweł Jarka, Barbara Hajduk, Pallavi Kumari, Henryk Janeczek, Marcin Godzierz, Yao Mawuena Tsekpo and Tomasz Tański
Polymers 2025, 17(5), 704; https://doi.org/10.3390/polym17050704 - 6 Mar 2025
Viewed by 450
Abstract
Herein, we report a comprehensive investigation on the thermal transitions of thin films of poly [2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione -3,6-diyl)-alt-(2,2′;5′,2″;5″,2′″-quaterthiophen-5,5′″-diyl)]PDPP4T, poly[2,6-(4,4-bis-(2-ethy-lhexyl)-4H-cyclopenta [2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] PCPDTBT, 1:1 blend of PDPP4T and PCPDTBT, and their composites with gold nanoparticles (AuNPs). The thermal transitions of these materials were studied using variable [...] Read more.
Herein, we report a comprehensive investigation on the thermal transitions of thin films of poly [2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione -3,6-diyl)-alt-(2,2′;5′,2″;5″,2′″-quaterthiophen-5,5′″-diyl)]PDPP4T, poly[2,6-(4,4-bis-(2-ethy-lhexyl)-4H-cyclopenta [2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] PCPDTBT, 1:1 blend of PDPP4T and PCPDTBT, and their composites with gold nanoparticles (AuNPs). The thermal transitions of these materials were studied using variable temperature spectroscopic ellipsometry (VTSE), with differential scanning calorimetry (DSC) serving as the reference method. Based on obtained VTSE results, for the first time, we have determined the phase diagrams of PDPP4T/PCPDTBT and their AuNPs composites. The VTSE measurements revealed distinct thermal transitions in the thin films, including characteristic temperatures corresponding to the pure phases of PDPP4T and PCPDTBT within their blends. These transitions were markedly different in the AuNPs composites compared to the neat materials, highlighting the unique interactions between the polymer matrix and AuNPs. Additionally, we explored the optical properties, surface morphology, and crystallinity of the materials. We hypothesize that the observed variations in thermal transitions, as well as the improvement in optical properties and crystallinity, are likely influenced by localized surface plasmon resonance (LSPR) and passivation phenomena induced by the AuNPs in the composite films. These findings could have important implications for the design and optimization of materials for optoelectronic applications. Full article
(This article belongs to the Special Issue Modeling of Polymer Composites and Nanocomposites)
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17 pages, 7524 KiB  
Article
Bicomponent Electrospinning of PVDF-Based Nanofiber Membranes for Air Filtration and Oil–Water Separation
by Tianxue Feng, Lin Fu, Zhimei Mu, Wenhui Wei, Wenwen Li, Xiu Liang, Liang Ma, Yitian Wu, Xiaoyu Wang, Tao Wu, Meng Gao, Guanchen Xu and Xingshuang Zhang
Polymers 2025, 17(5), 703; https://doi.org/10.3390/polym17050703 - 6 Mar 2025
Viewed by 598
Abstract
Particulate matter (PM) and water pollution have posed serious hazards to human health. Nanofiber membranes (NFMs) have emerged as promising candidates for the elimination of PMs and the separation of oil–water mixtures. In this study, a polyvinylidene difluoride (PVDF)-based nanofiber membrane with an [...] Read more.
Particulate matter (PM) and water pollution have posed serious hazards to human health. Nanofiber membranes (NFMs) have emerged as promising candidates for the elimination of PMs and the separation of oil–water mixtures. In this study, a polyvinylidene difluoride (PVDF)-based nanofiber membrane with an average diameter of approximately 150 nm was prepared via a double-nozzle electrospinning technology, demonstrating high-efficiency PM filtration and oil–water separation. The finer fiber diameter not only enhances PM filtration efficiency but also reduces air resistance. The high-voltage electric field and mechanical stretching during electrospinning promote high crystallization of β-phase PVDF. Additionally, the electrostatic charges generated on the surface of β-phase PVDF facilitate the adsorption of PM from the atmosphere. The introduction of polydopamine (PDA) in PVDF produces abundant adsorption sites, enabling outstanding filtration performance. PVDF-PVDF/PDA NFMs can achieve remarkable PM0.3 filtration efficiency (99.967%) while maintaining a low pressure drop (144 Pa). PVDF-PVDF/PDA NFMs are hydrophobic, and its water contact angle (WCA) is 125.9°. It also shows excellent resistance to both acidic and alkaline environments, along with notable flame retardancy, as it can self-extinguish within 3 s. This nanofiber membrane holds significant promise for applications in personal protection, indoor air filtration, oily wastewater treatment, and environmental protection. Full article
(This article belongs to the Special Issue Polymer-Based Flexible Materials, 3rd Edition)
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27 pages, 6163 KiB  
Article
Kinetic Study of In Vitro Release of Neem from Chitosan Biopolymer and Assessment of Its Biological Effectiveness
by Yasodani Nishshanka, Charitha Thambiliyagodage and Madara Jayanetti
Polymers 2025, 17(5), 702; https://doi.org/10.3390/polym17050702 - 6 Mar 2025
Viewed by 439
Abstract
The study examined the sustained release of neem from the polymeric carrier system chitosan by varying the drug content, ionic strength of the release medium, and pH. Six different kinetic models, i.e., Korsmeyer–Peppas (KP), Peppas–Sahlin (PS), Higuchi, Hixson–Crowell, Zero order, and First order [...] Read more.
The study examined the sustained release of neem from the polymeric carrier system chitosan by varying the drug content, ionic strength of the release medium, and pH. Six different kinetic models, i.e., Korsmeyer–Peppas (KP), Peppas–Sahlin (PS), Higuchi, Hixson–Crowell, Zero order, and First order were used to investigate the drug release kinetics. Based on the R2 values, the KP and PS models were chosen from the examined models to study the drug release mechanism from the chitosan biopolymer. The values found for model parameters n and m in the KP and PS models differ noticeably, suggesting that Fickian diffusion and Case II relaxation are important components of the neem release mechanism from chitosan. At lower ionic strengths and lower pH values, neem is released from the composite mostly by Fickian diffusion. The diphenyl-2-picrylhydrazyl assay served to assess the composite’s antioxidant properties. The composite’s antioxidant properties ranged from 3.56 ± 1.89% at 10 μg/mL to 51.28 ± 1.14% at 70 μg/mL. The ability of the composite to inhibit the denaturation of egg albumin was also tested and it ranged from 59.68 ± 0.93% at 25 μg/mL to 187.63 ± 3.53% at 1600 μg/mL. The drug composite has exhibited antibacterial activity against Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, and proved to be highly effective against P. aeruginosa at lower concentrations and against S. aureus at higher concentrations. The resulting inhibition zones for P. aeruginosa at 5 and 10 mg/mL concentrations were 16.5 ± 2.25 mm, and 14.83 ± 0.6 mm, respectively, whereas for S. aureus, it was 16.67 ± 0.33 mm at 20 mg/mL. The neem–chitosan composite’s minimum inhibitory concentration/minimum bactericidal concentration ratio for K. pneumoniae, P. aeruginosa, and S. aureus was greater than 4, suggesting that they trigger bacteriostatic outcomes, whereas for E. coli, it was 4, which means that bactericidal effects were evident. Full article
(This article belongs to the Special Issue Polymer-Based Materials for Drug Delivery and Biomedical Applications)
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16 pages, 12999 KiB  
Article
One-Pot Synthesis of Amphiphilic Linear and Hyperbranched Polyelectrolytes and Their Stimuli-Responsive Self-Assembly in Aqueous Solutions
by Angelica Maria Gerardos, Aleksander Forys, Barbara Trzebicka and Stergios Pispas
Polymers 2025, 17(5), 701; https://doi.org/10.3390/polym17050701 - 6 Mar 2025
Viewed by 443
Abstract
Stimuli-responsive polymeric nanostructures are compelling vectors for a wide range of application opportunities. The objective we sought was to broaden the array of self-assembling amphiphilic copolymers with stimuli-responsive characteristics by introducing a hydrophilic tunable monomer, (2-dimethylamino)ethyl methacrylate (DMAEMA), together with a hydrophilic one, [...] Read more.
Stimuli-responsive polymeric nanostructures are compelling vectors for a wide range of application opportunities. The objective we sought was to broaden the array of self-assembling amphiphilic copolymers with stimuli-responsive characteristics by introducing a hydrophilic tunable monomer, (2-dimethylamino)ethyl methacrylate (DMAEMA), together with a hydrophilic one, lauryl methacrylate (LMA), within linear and branched copolymer topologies. Size exclusion chromatography was used to evaluate the resultant linear and hyperbranched copolymers’ molecular weight and dispersity, and FT-IR and 1H-NMR spectroscopy techniques were used to delineate their chemical structure. The structural changes in the obtained self-organized supramolecular structures were thoroughly investigated using aqueous media with varying pH and salinity by dynamic light scattering (DLS), fluorescence spectroscopy (FS), and transmission electron microscopy (TEM). The nanoscale assemblies formed by the amphiphiles indicate significant potential for applications within the field of nanotechnology. Full article
(This article belongs to the Special Issue Advances and Applications of Block Copolymers II)
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16 pages, 10600 KiB  
Article
Identification of Aged Polypropylene with Machine Learning and Near–Infrared Spectroscopy for Improved Recycling
by Keyu Zhu, Delong Wu, Songwei Yang, Changlin Cao, Weiming Zhou, Qingrong Qian and Qinghua Chen
Polymers 2025, 17(5), 700; https://doi.org/10.3390/polym17050700 - 6 Mar 2025
Viewed by 529
Abstract
The traditional plastic sorting process primarily relies on manual operations, which are inefficient, pose safety risks, and result in suboptimal separation efficiency for mixed waste plastics. Near–infrared (NIR) spectroscopy, with its rapid and non–destructive analytical capabilities, presents a promising alternative. However, the analysis [...] Read more.
The traditional plastic sorting process primarily relies on manual operations, which are inefficient, pose safety risks, and result in suboptimal separation efficiency for mixed waste plastics. Near–infrared (NIR) spectroscopy, with its rapid and non–destructive analytical capabilities, presents a promising alternative. However, the analysis of NIR spectra is often complicated by overlapping peaks and complex data patterns, limiting its direct applicability. This study establishes a comprehensive machine learning–based NIR spectroscopy model to distinguish polypropylene (PP) at different aging stages. A dataset of NIR spectra was collected from PP samples subjected to seven simulated aging stages, followed by the construction of a classification model to analyze these spectral variations. The aging of PP was confirmed using Fourier–transform infrared spectroscopy (FTIR). Mechanical property analysis, including tensile strength and elongation at break, revealed a gradual decline with prolonged aging. After 40 days of accelerated aging, the elongation at the break of PP dropped to approximately 30%, retaining only about one–sixth of its original mechanical performance. Furthermore, various spectral preprocessing methods were evaluated to identify the most effective technique. The combination of the second derivative method with a linear –SVC achieved a classification accuracy of 99% and a precision of 100%. This study demonstrates the feasibility of the accurate identification of PP at different aging stages, thereby enhancing the quality and efficiency of recycled plastics and promoting automated, precise, and sustainable recycling processes. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
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21 pages, 5194 KiB  
Article
Influence of Surface Treatment and Protracted Ageing on the Shear Bond Strength of Orthodontic Brackets to Two Digitally Fabricated (Milled and 3D-Printed) Polymethacrylate-Based Provisional Crowns
by Nisreen Nabiel Hassan, Khurshid Mattoo, Atheer Khawaji, Hanan Najmi, Almaha Sadeli, Ahid Amer Alshahrani, Abeer Ali Qahtani, Abdullah Hasan Alshehri, Mai Almarzouki and Mohammed E. Sayed
Polymers 2025, 17(5), 699; https://doi.org/10.3390/polym17050699 - 6 Mar 2025
Viewed by 478
Abstract
This study determined the influence of surface treatment and protracted ageing on the shear bond strength (SBS) of orthodontic brackets bonded to CADCAM (milled) and 3D-printed polymethylmethacrylate (PMMA) provisional crowns (PCs). Eighty disc-shaped specimens [forty milled (CopraTemp WhitePeaks) [group (Gp) M] and forty [...] Read more.
This study determined the influence of surface treatment and protracted ageing on the shear bond strength (SBS) of orthodontic brackets bonded to CADCAM (milled) and 3D-printed polymethylmethacrylate (PMMA) provisional crowns (PCs). Eighty disc-shaped specimens [forty milled (CopraTemp WhitePeaks) [group (Gp) M] and forty printed (Asiga DentaTooth) (Gp P)] were divided into eight subgroups (Gp) based on surface treatment [no treatment (control) (Gp MC and Gp PC), coarse diamond (Gp MCD and Gp PCD), fine diamond (Gp MFD, and GP PFD) and sandblast (Gp MSB and Gp PSB)]. Orthodontic brackets were bonded (Assure Plus, Transbond XT), thermocycled (2200 cycles), and tested for SBS and failure (Adhesive Remnant Index) (ARI). Statistical tests included analysis of variance (ANOVA); Kruskal–Wallis (ARI ranks); and post hoc (Tukey, Dunn, and Bonferroni) for determining group differences at predetermined probability p-values less than 0.05. SBS was significantly increased in Gp MSB (15.51 Mpa) and Gp PSB (14.11 Mpa), while the coarse diamond subgroups yielded the lowest mean SBS values [Gp MCD (11.28 Mpa) and Gp PCD (11.62 Mpa)]. The SBS of subgroups MFD, MSB, PCD, and PSB showed significant differences from those of their respective controls (Gp MC and Gp PC). Low ARI scores were observed in Gp MC (0.40) and Gp MSB (0.80), while higher scores were observed in Gp PCD (2.10). Both milled and printed PCs fulfil the clinical criteria of the minimum SBS for orthodontic brackets for long-term use. However, milled PC has better SBS and low ARI scores, which make it more clinically feasible for orthodontic treatments. Full article
(This article belongs to the Special Issue Functional Polymeric Materials for Dental and Oral and Maxillofacial Surgery Applications)
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20 pages, 10269 KiB  
Article
Viscoelasticity of PPA/SBS/SBR Composite Modified Asphalt and Asphalt Mixtures Under Pressure Aging Conditions
by Zongjie Yu, Xinpeng Ling, Ze Fan, Yueming Zhou and Zhu Ma
Polymers 2025, 17(5), 698; https://doi.org/10.3390/polym17050698 - 6 Mar 2025
Viewed by 419
Abstract
The viscoelastic behavior of asphalt mixtures is a crucial consideration in the analysis of pavement mechanical responses and structural design. This study aims to elucidate the molecular structure and component evolution trends of polyphosphoric acid (PPA)/styrene butadiene styrene block copolymer (SBS)/styrene butadiene rubber [...] Read more.
The viscoelastic behavior of asphalt mixtures is a crucial consideration in the analysis of pavement mechanical responses and structural design. This study aims to elucidate the molecular structure and component evolution trends of polyphosphoric acid (PPA)/styrene butadiene styrene block copolymer (SBS)/styrene butadiene rubber copolymer (SBR) composite modified asphalt (CMA) under rolling thin film oven test (RTFOT) and pressure aging (PAV) conditions, as well as to analyze the viscoelastic evolution of CMA mixtures. First, accelerated aging was conducted in the laboratory through RTFOT, along with PAV tests for 20 h and 40 h. Next, the microscopic characteristics of the binder at different aging stages were explored using Fourier-transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) tests. Additionally, fundamental rheological properties and temperature sweep tests were performed to reveal the viscoelastic evolution characteristics of CMA. Ultimately, the viscoelastic properties of CMA mixtures under dynamic loading at different aging stages were clarified. The results indicate that the incorporation of SBS and SBR increased the levels of carbonyl and sulfoxide factors while decreasing the level of long-chain factors, which slowed down the rate of change of large molecule content and reduced the rate of change of LMS by more than 6%, with the rate of change of overall molecular weight distribution narrowing to below 50%. The simultaneous incorporation of SBS and SBR into CMA mixtures enhanced the dynamic modulus in the 25 Hz and −10 °C range by 24.3% (AC-13), 15.4% (AC-16), and reduced the φ by 55.8% (AC-13), 40% (AC-16). This research provides a reference for the application of CMA mixtures in the repair of pavement pothole damage. Full article
(This article belongs to the Special Issue Mechanical and Dynamic Characterization of Polymeric Composites, 2nd Edition)
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16 pages, 1937 KiB  
Article
Utilizing Essential Oil Components as Natural Antifungal Preservatives in the Active Packaging of Bread
by Konstantinos Safakas, Georgia C. Lainioti, George Tsiamis, Panagiota Stathopoulou and Athanasios Ladavos
Polymers 2025, 17(5), 697; https://doi.org/10.3390/polym17050697 - 6 Mar 2025
Viewed by 650
Abstract
The use of essential oil components as natural antifungal preservatives in the active packaging of bread is an innovative approach that leverages the antimicrobial properties of these compounds to extend the shelf life of bread and ensure its safety. The aim of the [...] Read more.
The use of essential oil components as natural antifungal preservatives in the active packaging of bread is an innovative approach that leverages the antimicrobial properties of these compounds to extend the shelf life of bread and ensure its safety. The aim of the present work was the thorough investigation of the antioxidant properties and antifungal activity of low-density polyethylene (LDPE or PE) nanocomposite films with organically modified montmorillonite (O) loaded with carvacrol (C) or thymol (T) as a function of time, starting from 2 months and concluding at 12 months. The films PE_OC and PE_OT were prepared through the evaporation/adsorption method, a green methodology developed by our group compatible with food packaging. For a comprehensive analysis of the synthesized films’ oxygen permeability (OTR), measurements were employed, indicating that the incorporation of clay–bioactive nanocarriers into LDPE films reduced their oxygen permeability. A thorough analysis in terms of the antioxidant activity of the films was assessed at various intervals (2, 3, 6, and 12 months), showing high antioxidant activity for films PE_OC10 and PE_OT10 (polyethylene with 10% wt. organically modified montmorillonite loaded with carvacrol or thymol), even at 12 months. Based on the overall analysis, the PE_OC10 film was identified as the most effective option in the antifungal evaluation conducted using white bread, demonstrating substantial inhibition of fungal growth for up to six months. Full article
(This article belongs to the Special Issue Advanced Polymers in Food Industry II)
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18 pages, 12446 KiB  
Article
Dynamic Behavior of Carbon Nanotube-Reinforced Polymer Composite Ring-like Structures: Unraveling the Effects of Agglomeration, Porosity, and Elastic Coupling
by Hossein Mottaghi T., Moein A. Ghandehari and Amir R. Masoodi
Polymers 2025, 17(5), 696; https://doi.org/10.3390/polym17050696 - 5 Mar 2025
Viewed by 486
Abstract
This research examines the free vibration characteristics of composite ring-like structures enhanced with carbon nanotubes (CNTs), taking into account the effects of CNT agglomeration. The structural framework comprises two concentric composite rings linked by elastic springs, creating a coupled beam ring (CBR) system. [...] Read more.
This research examines the free vibration characteristics of composite ring-like structures enhanced with carbon nanotubes (CNTs), taking into account the effects of CNT agglomeration. The structural framework comprises two concentric composite rings linked by elastic springs, creating a coupled beam ring (CBR) system. The first-order shear deformation theory (FSDT) is applied to account for transverse shear deformation, while Hamilton’s principle is employed to formulate the governing equations of motion. The effective mechanical properties of the composite material are assessed with regard to CNT agglomeration, which has a significant impact on the elastic modulus and the overall dynamic behavior of the structure. The numerical analysis explores the influence of porosity distribution, boundary conditions (BCs), and the stiffness of the springs on the natural vibration frequencies (NVFs). The results demonstrate that an increase in CNT agglomeration leads to a reduction in the stiffness of the composite, consequently decreasing the NVFs. Furthermore, asymmetric porosity distributions result in nonlinear fluctuations in NVFs due to irregularities in mass and stiffness, whereas uniform porosity distributions display a nearly linear relationship. This study also emphasizes the importance of boundary conditions and elastic coupling in influencing the vibrational response of CBR systems. These findings offer significant insights for the design and optimization of advanced composite ring structures applicable in aerospace, nanotechnology, and high-performance engineering systems. Full article
(This article belongs to the Special Issue Structure, Properties and Applications of Polymer-Based Nanocomposites)
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14 pages, 3309 KiB  
Article
Self-Toughened Epoxy Resin via Hybridization of Structural Isomeric Curing Agents
by Woong Kwon, Jiyeon Cheon, Hei Je Jeong, Jong Sung Won, Byeong-Joo Kim, Man Young Lee, Seung Geol Lee and Euigyung Jeong
Polymers 2025, 17(5), 695; https://doi.org/10.3390/polym17050695 - 5 Mar 2025
Viewed by 532
Abstract
Fracture toughness is a key property of epoxy resins with a high glass transition temperature (Tg), used in carbon fiber/epoxy composites for aerospace applications. Conventional toughening methods rely on adding toughening agents, often compromising the processibility and thermal stability. This study [...] Read more.
Fracture toughness is a key property of epoxy resins with a high glass transition temperature (Tg), used in carbon fiber/epoxy composites for aerospace applications. Conventional toughening methods rely on adding toughening agents, often compromising the processibility and thermal stability. This study introduces a simple self-toughening approach that enhances the fracture toughness without sacrificing other properties by controlling the cured epoxy network structure. Tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) epoxy resin was cured using mixtures of structural isomeric curing agents, 3,3′- and 4,4′-diaminodiphenyl sulfone (3,3′- and 4,4′-DDS), at ratios of 7:3, 5:5, and 3:7. The optimal 7:3 ratio produced a resin with 30% higher fracture toughness compared to TGDDM/3,3′-DDS and 100% higher than the TGDDM/4,4′-DDS system. The Tg of the self-toughened resin ranged from 241 to 266 °C, which was intermediate between the Tg values of the TGDDM/3,3′-DDS and TGDDM/4,4′-DDS systems. This improvement is attributed to the higher crosslink density and reduced free volume of the epoxy network. These findings demonstrate that simply mixing isomeric curing agents enables self-toughening, providing a practical and efficient strategy to enhance the performance of high-Tg epoxy resins in advanced composite applications. Full article
(This article belongs to the Special Issue Development in Epoxy Polymers)
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29 pages, 9288 KiB  
Article
Machine Learning-Driven Prediction of Composite Materials Properties Based on Experimental Testing Data
by Khrystyna Berladir, Katarzyna Antosz, Vitalii Ivanov and Zuzana Mitaľová
Polymers 2025, 17(5), 694; https://doi.org/10.3390/polym17050694 - 5 Mar 2025
Viewed by 912
Abstract
The growing demand for high-performance and cost-effective composite materials necessitates advanced computational approaches for optimizing their composition and properties. This study aimed at the application of machine learning for the prediction and optimization of the functional properties of composites based on a thermoplastic [...] Read more.
The growing demand for high-performance and cost-effective composite materials necessitates advanced computational approaches for optimizing their composition and properties. This study aimed at the application of machine learning for the prediction and optimization of the functional properties of composites based on a thermoplastic matrix with various fillers (two types of fibrous, four types of dispersed, and two types of nano-dispersed fillers). The experimental methods involved material production through powder metallurgy, further microstructural analysis, and mechanical and tribological testing. The microstructural analysis revealed distinct structural modifications and interfacial interactions influencing their functional properties. The key findings indicate that optimal filler selection can significantly enhance wear resistance while maintaining adequate mechanical strength. Carbon fibers at 20 wt. % significantly improved wear resistance (by 17–25 times) while reducing tensile strength and elongation. Basalt fibers at 10 wt. % provided an effective balance between reinforcement and wear resistance (by 11–16 times). Kaolin at 2 wt. % greatly enhanced wear resistance (by 45–57 times) with moderate strength reduction. Coke at 20 wt. % maximized wear resistance (by 9−15 times) while maintaining acceptable mechanical properties. Graphite at 10 wt. % ensured a balance between strength and wear, as higher concentrations drastically decreased mechanical properties. Sodium chloride at 5 wt. % offered moderate wear resistance improvement (by 3–4 times) with minimal impact on strength. Titanium dioxide at 3 wt. % enhanced wear resistance (by 11–12.5 times) while slightly reducing tensile strength. Ultra-dispersed PTFE at 1 wt. % optimized both strength and wear properties. The work analyzed in detail the effect of PTFE content and filler content on composite properties based on machine learning-driven prediction. Regression models demonstrated high R-squared values (0.74 for density, 0.67 for tensile strength, 0.80 for relative elongation, and 0.79 for wear intensity), explaining up to 80% of the variability in composite properties. Despite its efficiency, the limitations include potential multicollinearity, a lack of consideration of external factors, and the need for further validation under real-world conditions. Thus, the machine learning approach reduces the need for extensive experimental testing, minimizing material waste and production costs, contributing to SDG 9. This study highlights the potential use of machine learning in polymer composite design, offering a data-driven framework for the rational choice of fillers, thereby contributing to sustainable industrial practices. Full article
(This article belongs to the Section Polymer Physics and Theory)
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15 pages, 3346 KiB  
Article
Development and Characterization of Antimicrobial Chitosan/Polyethylene Oxide/Bacterial Cellulose Nanofibers
by Fatma Sude Cetin, Tubanur Avci, Emre Uygur, Elif Ilhan, Elif Kaya, Gulgun Bosgelmez Tinaz, Liviu Duta, Canan Dogan and Oguzhan Gunduz
Polymers 2025, 17(5), 693; https://doi.org/10.3390/polym17050693 - 5 Mar 2025
Viewed by 670
Abstract
This study introduces novel chitosan (CS) and polyethylene oxide (PEO) copolymers reinforced with bacterial cellulose (BC) to fabricate nanofibers using the electrospinning method. SEM analysis confirmed uniform nanofiber formation, with CS/PEO/BC nanofibers (~240 nm) exhibiting a larger diameter than CS/PEO ones (~190 nm). [...] Read more.
This study introduces novel chitosan (CS) and polyethylene oxide (PEO) copolymers reinforced with bacterial cellulose (BC) to fabricate nanofibers using the electrospinning method. SEM analysis confirmed uniform nanofiber formation, with CS/PEO/BC nanofibers (~240 nm) exhibiting a larger diameter than CS/PEO ones (~190 nm). FTIR spectroscopy confirmed BC integration, while Differential scanning calorimetry analysis indicated minimal impact on glass transition temperature. Notably, as compared to CS/PEO nanofibers, the CS/PEO/BC ones demonstrated superior swelling capacity, accelerated biodegradation, and enhanced mechanical (i.e., tensile) properties, with maximum stress and strain values of ~3.41 MPa and ~0.01% vs. ~2.14 MPa and ~0.01%. Antimicrobial assays confirmed activity against bacterial strains, and biocompatibility tests showed high cell viability at day seven (99.26% for CS/PEO/BC nanofibers). These findings highlight the potential of CS/PEO/BC nanofibers as promising candidates for tissue engineering, offering improved strength, biodegradability, and antimicrobial properties. Full article
(This article belongs to the Special Issue Multifunctional Application of Electrospun Fiber)
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14 pages, 4358 KiB  
Article
Biocontrol Potential of Poly(3-hydroxybutyrate) Fibers Functionalized with Chitooligosaccharide/Bacillus subtilis Using Electrospinning and Electrospraying
by Nikoleta Stoyanova, Nasko Nachev, Mladen Naydenov, Iliyana Valcheva, Mariya Spasova and Olya Stoilova
Polymers 2025, 17(5), 692; https://doi.org/10.3390/polym17050692 - 5 Mar 2025
Viewed by 490
Abstract
Sustainable agriculture increasingly relies on biocontrol agents as eco-friendly solutions to combat plant diseases while improving soil health. In this context, species of the genus Bacillus, particularly Bacillus subtilis, have shown promise as effective biocontrol agents for plant diseases. This study [...] Read more.
Sustainable agriculture increasingly relies on biocontrol agents as eco-friendly solutions to combat plant diseases while improving soil health. In this context, species of the genus Bacillus, particularly Bacillus subtilis, have shown promise as effective biocontrol agents for plant diseases. This study demonstrates the successful fabrication of biohybrid materials by decorating electrospun poly(3-hydroxybutyrate) (PHB) fibers with electrosprayed chitooligosaccharide (COS) and Bacillus subtilis using simultaneous electrospinning and electrospraying. During electrospraying, COS formed a uniform film over the PHB fibers, serving as both an adhesive and a protective coating that maintained the viability and functionality of the embedded bacteria. SEM confirmed that bacterial spores were uniformly spread across the COS-coated biopolymer fibers. ATR-FTIR spectroscopy verified the successful deposition of COS on the fibers, while mechanical assay demonstrated enhancement in mechanical characteristics after the COS film formation on the PHB fibers compared to uncoated PHB. In addition, COS improved the wetting properties of the fibrous PHB material, creating a favorable environment for bacterial growth and development. Microbiological tests showed that the embedded B. subtilis remained viable and proliferated normally after 48 h under suitable conditions at 28 °C on agar medium. Furthermore, the biohybrid COS/B. subtilis-on-PHB materials also effectively inhibited the growth of pathogenic fungi, including species of Alternaria and Fusarium. These findings highlight the potential of dual electrospinning/electrospraying techniques for the fabrication of eco-friendly biocontrol formulations. The integration of COS coatings with B. subtilis provides a promising approach for sustainable agriculture by combining enhanced material properties with effective antifungal activity. Full article
(This article belongs to the Collection Electrospun Nanofibers)
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15 pages, 2354 KiB  
Article
Moisture-Driven Morphology Changes in the Thermal and Dielectric Properties of TPU-Based Syntactic Foams
by Sabarinathan Pushparaj Subramaniyan, Partha Pratim Das, Rassel Raihan and Pavana Prabhakar
Polymers 2025, 17(5), 691; https://doi.org/10.3390/polym17050691 - 5 Mar 2025
Viewed by 549
Abstract
Syntactic foams are a promising candidate for applications in marine, oil and gas industries in underwater cables and pipelines due to their excellent insulation properties. The effective transmission of electrical energy through cables requires insulation materials with a low loss factor and low [...] Read more.
Syntactic foams are a promising candidate for applications in marine, oil and gas industries in underwater cables and pipelines due to their excellent insulation properties. The effective transmission of electrical energy through cables requires insulation materials with a low loss factor and low dielectric constant. Similarly, in transporting fluid through pipelines, thermal insulation is crucial. However, both applications are susceptible to potential environmental degradation from moisture exposure, which can significantly impact the material’s properties. This study addresses the knowledge gap by examining the implications of prolonged moisture exposure on thermoplastic polyurethane elastomer (TPU) and TPU-derived syntactic foam via various multi-scale material characterization methods. This research investigates a flexible syntactic foam composed of TPU and glass microballoons (GMBs) fabricated through selective laser sintering. The study specifically examines the effects of moisture exposure over periods of 90 and 160 days, in conjunction with varying GMB volume fractions of 0%, 20%, and 40%. It aims to elucidate the resulting microphase morphological changes, their underlying mechanisms, and the subsequent impact on thermal transport and dielectric properties, all in comparison to unaged samples of the same material. Our findings reveal that increasing the volume fraction of GMB in TPU-based syntactic foam reduces its thermal conductivity and specific heat capacity. However, moisture exposure did not significantly affect the foam’s thermal conductivity. Additionally, we found that the dielectric constant of the syntactic foams decreases with increasing volume fraction of GMB and decreasing frequency of the applied field, which is due to limited molecular orientation in response to the field. Finally, moisture exposure affects the dielectric loss factor of TPU-based syntactic foams with GMBs, possibly due to the distribution morphology of hard and soft segments in TPU. Full article
(This article belongs to the Special Issue Thermoplastic Foams: Processing, Manufacturing, and Characterization)
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15 pages, 1643 KiB  
Article
The Environmental Analysis of the Post-Use Management Scenarios of the Heat-Shrinkable Film
by Patrycja Walichnowska, Józef Flizikowski, Andrzej Tomporowski, Marek Opielak and Wojciech Cieślik
Polymers 2025, 17(5), 690; https://doi.org/10.3390/polym17050690 - 5 Mar 2025
Viewed by 615
Abstract
The post-use management of plastic films, including shrink films, poses a significant environmental and technological challenge for the industry. Due to their durability and difficulty in degradation, these wastes contribute to environmental pollution, generating microplastics and greenhouse gas emissions during improper disposal. This [...] Read more.
The post-use management of plastic films, including shrink films, poses a significant environmental and technological challenge for the industry. Due to their durability and difficulty in degradation, these wastes contribute to environmental pollution, generating microplastics and greenhouse gas emissions during improper disposal. This paper examines different post-use management methods for shrink wrap, such as recycling, landfilling, and incineration, and assesses their impact on the environmental impact of the bottle packaging process using a life-cycle analysis (LCA). This study shows that the recycling option has the lowest potential environmental impact. Compared to other post-use management options, recycling reduces the potential environmental impact by more than 50%. The analysis also shows that the tested scenario using recycled film and photovoltaic energy has the lowest potential environmental impact. Using recycled film and powering the process with renewable energy reduces the potential environmental impact by about 95% compared to Scenario 1 and by about 85% in Scenario 3. Full article
(This article belongs to the Section Circular and Green Sustainable Polymer Science)
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19 pages, 12311 KiB  
Article
Rapid and Efficient Polymer/Contaminant Removal from Single-Layer Graphene via Aqueous Sodium Nitrite Rinsing for Enhanced Electronic Applications
by Kimin Lee, Juneyoung Kil, JaeWoo Park, Sui Yang and Byoungchoo Park
Polymers 2025, 17(5), 689; https://doi.org/10.3390/polym17050689 - 4 Mar 2025
Viewed by 721
Abstract
The removal of surface residues from single-layer graphene (SLG), including poly(methyl methacrylate) (PMMA) polymers and Cl− ions, during the transfer process remains a significant challenge with regard to preserving the intrinsic properties of SLG, with the process often leading to unintended doping [...] Read more.
The removal of surface residues from single-layer graphene (SLG), including poly(methyl methacrylate) (PMMA) polymers and Cl− ions, during the transfer process remains a significant challenge with regard to preserving the intrinsic properties of SLG, with the process often leading to unintended doping and reduced electronic performance capabilities. This study presents a rapid and efficient surface treatment method that relies on an aqueous sodium nitrite (NaNO2) solution to remove such contaminants effectively. The NaNO2 solution rinse leverages reactive nitric oxide (NO) species to neutralize ionic contaminants (e.g., Cl−) and partially oxidize polymer residues in less than 10 min, thereby facilitating a more thorough final cleaning while preserving the intrinsic properties of graphene. Characterization techniques, including atomic force microscopy (AFM), Kelvin probe force microscopy (KPFM), and X-ray photoelectron spectroscopy (XPS), demonstrated substantial reductions in the levels of surface residues. The treatment restored the work function of the SLG to approximately 4.79 eV, close to that of pristine graphene (~4.5–4.8 eV), compared to the value of nearly 5.09 eV for conventional SLG samples treated with deionized (DI) water. Raman spectroscopy confirmed the reduced doping effects and improved structural integrity of the rinsed SLG. This effective rinsing process enhances the reproducibility and performance of SLG, enabling its integration into advanced electronic devices such as organic light-emitting diodes (OLEDs), photovoltaic (PV) cells, and transistors. Furthermore, the technique is broadly applicable to other two-dimensional (2D) materials, paving the way for next-generation (opto)electronic technologies. Full article
(This article belongs to the Special Issue Graphene-Based Polymer Composites and Their Applications II)
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12 pages, 4102 KiB  
Article
Surface Modification of Organic Chromium-Free Tanned Leather Shavings and the Immobilization of Lipase
by Dongyan Hao, Xuechuan Wang, Jiajia Shi, Zhisheng Wang and Xing Zhu
Polymers 2025, 17(5), 688; https://doi.org/10.3390/polym17050688 - 4 Mar 2025
Viewed by 534
Abstract
Following the concept of “waste into resources”, a mild and controllable light grafting technique was used to immobilize pancreatic lipase (PPL) in situ on modified organic, chromium-free tanned leather scraps to catalyze the hydrolysis of waste oil. The experimental results showed that immobilized [...] Read more.
Following the concept of “waste into resources”, a mild and controllable light grafting technique was used to immobilize pancreatic lipase (PPL) in situ on modified organic, chromium-free tanned leather scraps to catalyze the hydrolysis of waste oil. The experimental results showed that immobilized PPL significantly improved the catalytic activity, operational stability, reusability, and storage stability compared to free PPL. Furthermore, the study evaluated the environmental compatibility of the system through biological risk assessment of soil extracts after degradation, indicating that the system has good environmental compatibility. The experiment is simple to operate, uses mild conditions, and the immobilized material is obtained from leather-making solid waste. The use of this immobilization system to treat waste oil in the leather-making process is of great significance for achieving clean and sustainable production in the leather industry. Full article
(This article belongs to the Section Circular and Green Sustainable Polymer Science)
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17 pages, 1434 KiB  
Article
Biopolymer-Based Microencapsulation of Procyanidins from Litchi Peel and Coffee Pulp: Characterization, Bioactivity Preservation, and Stability During Simulated Gastrointestinal Digestion
by María de los Ángeles Vázquez-Nuñez, Nuria E. Rocha-Guzmán, Pedro Aguilar-Zárate, Romeo Rojas, Guillermo Cristian G. Martínez-Ávila, Abigail Reyes and Mariela R. Michel
Polymers 2025, 17(5), 687; https://doi.org/10.3390/polym17050687 - 4 Mar 2025
Viewed by 1231
Abstract
The need for encapsulation processes in compounds such as procyanidins (PCs) is related to their functional stability, which may limit their application in functional foods. The aim of this study was to evaluate the in vitro digestion of microencapsulated PCs from litchi peel [...] Read more.
The need for encapsulation processes in compounds such as procyanidins (PCs) is related to their functional stability, which may limit their application in functional foods. The aim of this study was to evaluate the in vitro digestion of microencapsulated PCs from litchi peel and coffee pulp to determine concentration changes and antioxidant activity. The PCs were extracted, purified, encapsulated, and subjected to in vitro digestion and absorption. Phenolic acids, flavonoids, and PCs were characterized by UPLC-PDA-ESI-QqQ, identifying 27 compounds, including PCs with mean degrees of polymerization (mDP) of 1.2 and 1.7 for lychee and coffee. It was shown that the concentrations of encapsulated PCs were adequately retained during digestion (94.81 ± 4.83 and 90.74 ± 1.77%, lychee and coffee, respectively), with variation in their antioxidant capacity (68.33 ± 2.89 and 77.07 ± 4.59%); however, they showed better results than in their free form. Additionally, litchi PCs showed a higher absorption rate (100%) than coffee PCs (60%). These results allowed us to determine that encapsulation preserves the properties of the PCs and provides better conservation percentages than other studies, which could be a valuable addition to the functional ingredients market, offering greater value to these by-products. Full article
(This article belongs to the Special Issue Polymers and Their Interactions with Biotics in Food Science and Nutrition)
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14 pages, 4323 KiB  
Article
Use of Natamycin for the Development of Polymer Systems with Antifungal Activity for Packaging Applications
by Vincenzo Titone, Manuela Ceraulo, Francesco Lopresti, Giuliana Garofalo, Raimondo Gaglio, Maria Chiara Mistretta and Luigi Botta
Polymers 2025, 17(5), 686; https://doi.org/10.3390/polym17050686 - 4 Mar 2025
Viewed by 707
Abstract
Recently, there has been a rapid growth in the use of biodegradable polymers as alternatives to petroleum-based polymers, particularly in the packaging sector, to reduce environmental pollution. In this scenario, the aim of this work was to study the use of different amounts [...] Read more.
Recently, there has been a rapid growth in the use of biodegradable polymers as alternatives to petroleum-based polymers, particularly in the packaging sector, to reduce environmental pollution. In this scenario, the aim of this work was to study the use of different amounts of Natamycin on two polymer systems: one that is non-biodegradable but widely known in the field of packaging and one that is biodegradable and is emerging as a possible replacement, in order to accelerate progress toward the achievement of the sustainable development goals. Both systems were produced through melt mixing followed by compression moulding. Subsequently, they were fully characterized by rheological, morphological, mechanical, thermal, and wettability analyses. Natamycin release was evaluated in water at 4 °C by UV-Vis measurements. The antifungal activity of both polymeric systems containing Natamycin was assessed in vitro against three strains of undesirable filamentous fungi of food interest. The results show that PCL with 5% Natamycin represents an effective biodegradable alternative to EVA for inhibiting undesirable filamentous fungi. More specifically, both systems at 5% showed comparable inhibition zones of about 30 mm. Full article
(This article belongs to the Section Biobased and Biodegradable Polymers)
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22 pages, 12271 KiB  
Article
Unraveling of Poly(lactic acid) (PLA)/Natural Wax/Titanium Dioxide Nanoparticle Composites for Disposable Plastic Applications
by Jacqueline Guadalupe Bocarando-Chacón, Iván Alziri Estrada-Moreno, Imelda Olivas-Armendáriz, Alejandro Vega-Rios and Mónica Elvira Mendoza-Duarte
Polymers 2025, 17(5), 685; https://doi.org/10.3390/polym17050685 - 4 Mar 2025
Viewed by 674
Abstract
The present research is a comprehensive study that developed poly(lactic acid) PLA/natural wax (Wx)/non-functionalized titanium dioxide nanoparticles (TiO2-NF) and PLA/Wx/titanium dioxide nanoparticles functionalized with triethoxysilane (TiO2-F) composites by melt blending. This research systematically investigated their hydrolytic degradation, antibacterial properties, [...] Read more.
The present research is a comprehensive study that developed poly(lactic acid) PLA/natural wax (Wx)/non-functionalized titanium dioxide nanoparticles (TiO2-NF) and PLA/Wx/titanium dioxide nanoparticles functionalized with triethoxysilane (TiO2-F) composites by melt blending. This research systematically investigated their hydrolytic degradation, antibacterial properties, oxygen permeability, and optical transparency. The TiO2-NF or TiO2-F (0.1, 0.5, or 1 wt%) were added to a PLA/Wx (85:15) blend using a Brabender internal mixer at 180 °C. Hydrolytic degradation was carried out in distilled water at 50 °C and an initial pH of 6.2 for 9 months. Changes in weight, morphology, and the rheological behavior of the blends were evaluated at different times during the hydrolytic degradation of the PLA/Wx/TiO2-NF and PLA/Wx/TiO2-F composites. The antibacterial properties of PLA/Wx, PLA/Wx/TiO2-0.1-NF, and PLA/Wx/TiO2-0.1-F were assessed by testing them against both E. coli (Gram-negative) and S. aureus (Gram-positive) bacteria. Their oxygen permeability and optical transparency are comparable to those of LDPE films. These composites, produced by melt blending, show potential for application as disposable plastics, which could significantly impact the fields of materials science and polymer engineering. Full article
(This article belongs to the Special Issue Bio-Based and Biodegradable Polymers: Synthesis, Characterization and Applications)
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15 pages, 4153 KiB  
Article
Highly Branched Poly(Adipic Anhydride-Co-Mannitol Adipate): Synthesis, Characterization, and Thermal Properties
by Mahir A. Jalal, Einas A. Abood, Zainab J. Sweah, Hadi S. Al-Lami, Alyaa Abdulhasan Abdulkarem and Haider Abdulelah
Polymers 2025, 17(5), 684; https://doi.org/10.3390/polym17050684 - 4 Mar 2025
Viewed by 458
Abstract
In this study, modification of poly(adipic anhydride) through branching its chains was carried out via melt condensation polymerization with D-mannitol. The percentage of mannitol was varied (3, 4, 5, 10, 15, and 20 Wt.%) and the resulting copolymers were purified and characterized by [...] Read more.
In this study, modification of poly(adipic anhydride) through branching its chains was carried out via melt condensation polymerization with D-mannitol. The percentage of mannitol was varied (3, 4, 5, 10, 15, and 20 Wt.%) and the resulting copolymers were purified and characterized by FT-IR and 13C-NMR. These analyses indicated that linear chains of poly(adipic anhydride) can react with strong nucleophiles and dissociate to produce highly branched poly(adipic anhydride-co-mannitol adipate) which confirms the validity of the proposed mechanism. The copolymer’s molecular weight characteristics have been also examined using GPC analysis. Thermal properties of copolymers were also investigated using TGA, DTG, and DCS analyses. TGA/DTG revealed that the thermal degradation of copolymers proceeds in multi-stage decomposition, whereas the shift and pattern change of the melting point peak of DSC curves can identify the weight percentage of mannitol for homogenous copolymers. Two non-isothermal models, the Flynn–Wall–Ozawa and Kissinger methods, have been also employed to analyze thermogravimetric data collected from the thermal decomposition of the copolymers and found that Flynn–Wall–Ozawa method provides better results with R2 correlation up to 99.3%. The activation energy in the region of Tmax was determined and found that an increase in mannitol contents in copolymer has a positive impact on its thermal stability. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
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19 pages, 10502 KiB  
Article
Flexible and Washable Poly(3,4-ethylenedioxythiophene): Polystyrene Sulfonate/Polyvinyl Alcohol Fabric Dry Electrode for Long-Term Electroencephalography Signals Measurement
by Fangmeng Zeng, Guanghua Wang, Chenyi Sun, Jiayi Gao, Shanqun Ji and Quanxi Zhang
Polymers 2025, 17(5), 683; https://doi.org/10.3390/polym17050683 - 4 Mar 2025
Viewed by 493
Abstract
Recent advancements in smart textiles have facilitated their extensive application in wearable health monitoring, particularly in brain activity measurement. This study introduces a flexible and washable fabric dry electroencephalography (EEG) electrode designed for brain activity measurement. The fabric dry electrode is constructed from [...] Read more.
Recent advancements in smart textiles have facilitated their extensive application in wearable health monitoring, particularly in brain activity measurement. This study introduces a flexible and washable fabric dry electroencephalography (EEG) electrode designed for brain activity measurement. The fabric dry electrode is constructed from electrically conductive polyester fabric with a resistivity of 0.09 Ω·cm, achieved by applying a PEDOT: PSS/PVA conductive paste coating on the textile substrate. A comparative analysis of the tensile properties between the conductive and untreated polyester fabric was conducted. The SEM images demonstrated that the PEDOT: PSS/PVA conductive polymer composite resulted in a uniform coating on the fabric surface. When enveloped in elastic foam, the fabric dry electrode maintained a low and stable electrode–skin contact impedance during prolonged EEG monitoring. Additionally, the short circuit noise level of the fabric dry electrode exhibited superior performance compared to both Ag/AgCl wet and finger dry electrode. The EEG signals acquired from the fabric dry electrode were comparable to those recorded by the Ag/AgCl wet electrode. Moreover, the fabric electrode effectively captured clear and reliable EEG signals, even after undergoing 10 washing cycles. The fabric dry electrode indicates good sweat resistance and biocompatibility during prolonged monitoring. Full article
(This article belongs to the Section Smart and Functional Polymers)
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23 pages, 1716 KiB  
Article
Food-Grade Microwave-Assisted Depolymerization of Grape Seed Condensed Tannins: Optimizing the Reaction Using Gallic Acid as a Nucleophile
by Carolina F. Morales and Fernando A. Osorio
Polymers 2025, 17(5), 682; https://doi.org/10.3390/polym17050682 - 4 Mar 2025
Viewed by 427
Abstract
Food waste has a significant social impact but can be revalued as a source of bioactive compounds, such as condensed tannins. This abundant biomass, corresponding to a polymeric antioxidant, must be depolymerized to become bioavailable. Previous studies have investigated polymer degradation into oligomers [...] Read more.
Food waste has a significant social impact but can be revalued as a source of bioactive compounds, such as condensed tannins. This abundant biomass, corresponding to a polymeric antioxidant, must be depolymerized to become bioavailable. Previous studies have investigated polymer degradation into oligomers using high temperatures and expensive nucleophiles, often under conditions unsuitable for food applications. In the present investigation, it is proposed that the depolymerization of condensed tannins can occur under food-grade conditions using a Generally Recognized as Safe (GRAS) solvent by optimizing the reaction’s heating method with microwave assistance and using gallic acid as a nucleophile. Thermal studies indicate that the degradation of total polyphenols content follows first-order kinetics and occurs above 80 °C in microwave. Depolymerization follows second-order kinetics, yielding epicatechin as the primary product with zero-order formation kinetics. The optimized factors were 80% v/v ethanol, 10 mg/mL polymeric tannins, and 5.88 mg/mL gallic acid. Under these conditions, the reaction efficiency was 99.9%, the mean particle diameter was 5.7 nm, the total polyphenols content was 297.3 ± 15.9 EAG mg/g, and the inhibition of ABTS●+ and DPPH● radicals was 93.5 ± 0.9% and 88.2 ± 1.5%, respectively. These results are promising for future scaling processes. Full article
(This article belongs to the Section Polymer Chemistry)
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14 pages, 11251 KiB  
Article
Josef Albers’ Structural Constellations: Investigating Formulations of Laminated Plastics Through Correlating the Industrial Literature with Scientific Analysis
by Maria Kokkori, Hortense de La Codre and Madeline C. Meier
Polymers 2025, 17(5), 681; https://doi.org/10.3390/polym17050681 - 4 Mar 2025
Viewed by 471
Abstract
Josef Albers’ Structural Constellations series, created between 1948 and 1966, represents a pioneering exploration of plastic laminates as an artistic medium. Leveraging the unique properties of these materials, including their smooth surfaces, vibrant coloration, and precision in router engraving, Albers created machine-engraved works [...] Read more.
Josef Albers’ Structural Constellations series, created between 1948 and 1966, represents a pioneering exploration of plastic laminates as an artistic medium. Leveraging the unique properties of these materials, including their smooth surfaces, vibrant coloration, and precision in router engraving, Albers created machine-engraved works featuring intricate geometric compositions. This study combines archival research with scientific analysis to examine over fifty artworks and archival samples from the Josef and Anni Albers Foundation (1948–1970). Fourier-transform infrared (FTIR) spectroscopy and digital microscopy were employed to identify polymer types and analyze surface morphologies. Chemometric methods were applied to process the substantial dataset, offering key insights into Albers’ evolving material choices and their impact on the visual and structural properties of his works. Full article
(This article belongs to the Special Issue Polymeric Materials in Modern and Contemporary Art, 3rd Edition)
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25 pages, 8101 KiB  
Article
Frontal Polymerization of Epoxy Resins: Kinetic Modeling, Rate Regulation and Curing Process Simulation for Space Manufacturing Applications
by Haisheng Wu, Yizhuo Gu, Xinyu Liu and Chaobo Xin
Polymers 2025, 17(5), 680; https://doi.org/10.3390/polym17050680 - 4 Mar 2025
Viewed by 532
Abstract
Frontal polymerization (FP) technology has attracted significant attention as an efficient, low-energy curing method for thermosetting resins. By enabling self-sustaining polymerization reactions, FP significantly reduces curing time and minimizes external energy dependence, making it ideal for in-orbit manufacturing applications. In contrast to traditional [...] Read more.
Frontal polymerization (FP) technology has attracted significant attention as an efficient, low-energy curing method for thermosetting resins. By enabling self-sustaining polymerization reactions, FP significantly reduces curing time and minimizes external energy dependence, making it ideal for in-orbit manufacturing applications. In contrast to traditional curing methods, which are limited by high energy consumption and low efficiency, FP offers a more efficient and flexible alternative. Nonetheless, the FP process is sensitive to material composition, processing and environmental factors, requiring systematic studies to enhance performance. This work focuses on reaction mechanisms, curing kinetics and processing factors of a self-developed FP epoxy resin system. The revealed curing mechanism and kinetics reveals a high initiation energy barrier and rapid curing characteristics, showing appropriate reaction inertness before initiation and stable reaction without continuous external energy input. The influences of initiator concentration and epoxy resin type on polymerization rate and the properties of cured resin were examined. Additionally, a curing simulation method validated by the experiment were employed to analyze the effects of mold material, resin cross-sectional area, initial temperature and environmental conditions on polymerization behavior. The results provide valuable insights for optimizing FP, advancing the understanding of the curing process and improving resin performance in space-based applications. Full article
(This article belongs to the Section Polymer Chemistry)
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15 pages, 4679 KiB  
Article
Preparation of 3-Iodo-2-propargyl-butyl-carbamate-Loaded Microcapsules for Long-Term Mold Resistance in Bamboo
by Gege Bao, Lu He, Xiaofeng Zhang, Xi Yu, Jingpeng Li and Daochun Qin
Polymers 2025, 17(5), 679; https://doi.org/10.3390/polym17050679 - 4 Mar 2025
Viewed by 504
Abstract
Bamboo, recognized as a nutrient-dense biomass material, exhibits a high susceptibility to mold infestations, which can result in discoloration and a notable decrease in longevity, thereby posing potential health risks to humans. In this study, melamine-formaldehyde resin (MFR) was utilized to load 3-iodo-2-propargyl-butyl-carbamate [...] Read more.
Bamboo, recognized as a nutrient-dense biomass material, exhibits a high susceptibility to mold infestations, which can result in discoloration and a notable decrease in longevity, thereby posing potential health risks to humans. In this study, melamine-formaldehyde resin (MFR) was utilized to load 3-iodo-2-propargyl-butyl-carbamate (IPBC) via in situ polymerization, resulting in the preparation of microcapsules suitable for anti-mold protection of bamboo. The mold resistance of Aspergillus niger, Trichoderma viride, and Penicillium citrinum were evaluated. A scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier-transform infrared spectrometer (FTIR), and thermogravimetric analysis (TG) were used to characterize and analyze the formation process, surface morphology, structural composition, and thermal stability of the microcapsules. The effects of different surfactants (Span 80, Tween 80, SDBS, SDS, GA) on the microscopic morphology of the anti-mold microcapsules were investigated. The results show that microcapsules prepared with Tween 80 as the surfactant exhibited good mold resistance. After coating MFR with IPBC, the drug loading of I-MFR is 20%, with an encapsulation efficiency of 80%, demonstrating excellent anti-mold performance. The microcapsules show favorable anti-mold performance and have broad application prospects in bamboo protection. Full article
(This article belongs to the Special Issue Eco-Friendly Supramolecular Polymeric Materials, 2nd Edition)
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22 pages, 9640 KiB  
Article
Dissipative Particle Dynamics: Simulation of Chitosan–Citral Microcapsules
by Wensheng Wu, Zhiwei Li, Dachun Feng, Qing Tang, Shuijiao Liu and Wenjing Lin
Polymers 2025, 17(5), 678; https://doi.org/10.3390/polym17050678 - 3 Mar 2025
Viewed by 620
Abstract
In this paper, the dissipative particle dynamics (DPD) method is used to simulate the self-assembly process, appearance, mesoscopic structure, and wrapping properties of microcapsules formed with citral as the core material and chitosan and sodium alginate as the single-wall materials, and with citral [...] Read more.
In this paper, the dissipative particle dynamics (DPD) method is used to simulate the self-assembly process, appearance, mesoscopic structure, and wrapping properties of microcapsules formed with citral as the core material and chitosan and sodium alginate as the single-wall materials, and with citral as the core material and chitosan-sodium alginate, chitosan–methylcellulose, sodium alginate–chitosan, and sodium alginate–methylcellulose as the double-wall materials. The effects of chitosan content and wall material composition on the structure, morphology, encapsulation performance, and stability of microcapsules are compared and analyzed. In addition, the microcapsules are deeply analyzed by using the mesoscopic structure, radial distribution function, and diffusion coefficient. This study provides a new idea and method for the preparation of citral microcapsules, and is of great significance for the design and development of new composite wall microcapsules. Full article
(This article belongs to the Special Issue Advances of Chitin and Chitosan-Based Materials: Preparation and Applications)
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28 pages, 8366 KiB  
Article
Artificial Neural Network Modeling of Mechanical Properties of 3D-Printed Polyamide 12 and Its Fiber-Reinforced Composites
by Catalin Fetecau, Felicia Stan and Doina Boazu
Polymers 2025, 17(5), 677; https://doi.org/10.3390/polym17050677 - 3 Mar 2025
Viewed by 657
Abstract
Fused filament fabrication (FFF) has recently emerged as a sustainable digital manufacturing technology to fabricate polymer composite parts with complex structures and minimal waste. However, FFF-printed composite parts frequently exhibit heterogeneous structures with low mechanical properties. To manufacture high-end parts with good mechanical [...] Read more.
Fused filament fabrication (FFF) has recently emerged as a sustainable digital manufacturing technology to fabricate polymer composite parts with complex structures and minimal waste. However, FFF-printed composite parts frequently exhibit heterogeneous structures with low mechanical properties. To manufacture high-end parts with good mechanical properties, advanced predictive tools are required. In this paper, Artificial Neural Network (ANN) models were developed to evaluate the mechanical properties of 3D-printed polyamide 12 (PA) and carbon fiber (CF) and glass fiber (GF) reinforced PA composites. Tensile samples were fabricated by FFF, considering two input parameters, such as printing orientation and infill density, and tested to determine the mechanical properties. Then, single- and multi-target ANN models were trained using the forward propagation Levenberg–Marquardt algorithm. Post-training performance analysis indicated that the ANN models work efficiently and accurately in predicting Young’s modulus and tensile strength of the 3D-printed PA and fiber-reinforced PA composites, with most relative errors being far less than 5%. In terms of mechanical properties, such as Young’s modulus and tensile strength, the 3D-printed composites outperform the unreinforced PA. Printing PA composites with 0° orientation and 100% infill density results in a maximum increase in Young’s modulus (up to 98% for CF/PA and 32% for GF/PA) and tensile strength (up to 36% for CF/PA and 18% for GF/PA) compared to the unreinforced PA. This study underscores the potential of the ANN models to predict the mechanical properties of 3D-printed parts, enhancing the use of 3D-printed PA composite components in structural applications. Full article
(This article belongs to the Special Issue 3D Printing of Polymer Composite Materials)
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11 pages, 3237 KiB  
Article
Biofilm Formation on Three High-Performance Polymeric CAD/CAM Composites: An In Vitro Study
by Sarah Almuhayya, Reema Alshahrani, Rehaf Alsania, Alhanoof Albassam, Hammad Alnemari and Rua Babaier
Polymers 2025, 17(5), 676; https://doi.org/10.3390/polym17050676 - 3 Mar 2025
Viewed by 615
Abstract
Reinforced polymeric materials are investigated as novel non-metal alternatives for prosthetic frameworks. This study examined the adherence of Streptococcus mutans to three high-performance polymeric (HPP) composites focusing on their microstructural composition, wettability, and surface roughness. Three CAD/CAM HPP composites [two fiber-reinforced composites, CarboCad [...] Read more.
Reinforced polymeric materials are investigated as novel non-metal alternatives for prosthetic frameworks. This study examined the adherence of Streptococcus mutans to three high-performance polymeric (HPP) composites focusing on their microstructural composition, wettability, and surface roughness. Three CAD/CAM HPP composites [two fiber-reinforced composites, CarboCad (CC) and TRINIA (TR), and one ceramic-reinforced polyether ether ketone, DentoPEEK (PK)], were sectioned into ten beam- and ten plate-shaped specimens from each material. Surface properties (n = 10) were analyzed by water wettability and roughness measurements (Ra and Rz). The biofilm adherence was determined by calculating the number of S. mutans through colony-forming units (CFUs). Representative images were obtained using a confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM). The data were analyzed using Welch one-way ANOVA and Dunnett T3 post hoc tests. The results showed significant differences in roughness (Ra) across the materials, ranked from highest to lowest as follows: TR, 0.231 µm; CC, 0.194 µm; and PK, 0.161 µm (p = 0.0001). The contact angle averages varied from 51.36° to 91.03°, with PK exhibiting the highest wettability (p = 0.0012). However, S. mutans adherence was markedly reduced in PK (1.96 CFU/mm2, p = 0.0001) in comparison to TR and CC (2.86 and 2.98 CFU/mm2, respectively). Consequently, the fiber-reinforced composites (CC and TR), despite their low wettability, exhibited greater susceptibility for bacterial adherence than the smoother and more wettable PK, highlighting the substantial impact of their surface roughness and microstructural variability. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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