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17 pages, 4727 KB

Open AccessArticle

Buckling and Post-Buckling Behaviour of a Carbon Fibre-Reinforced Polymer Stiffened Panel: A Numerical and Experimental Study

by Andrea Sellitto, Angela Russo, Mauro Zarrelli, Valeria Vinti, Luigi Trinchillo, Pierluigi Perugini and Aniello Riccio

Polymers 2026, 18(9), 1068; https://doi.org/10.3390/polym18091068 - 28 Apr 2026

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Abstract

The buckling and post-buckling responses of carbon fibre-reinforced polymer (CFRP) structures are strongly affected by geometric imperfections, boundary conditions, and material nonlinearities, making their reliable numerical prediction challenging. This work presents an integrated experimental–numerical investigation of a stiffened CFRP panel subjected to compressive [...] Read more.

The buckling and post-buckling responses of carbon fibre-reinforced polymer (CFRP) structures are strongly affected by geometric imperfections, boundary conditions, and material nonlinearities, making their reliable numerical prediction challenging. This work presents an integrated experimental–numerical investigation of a stiffened CFRP panel subjected to compressive loading, with the aim of improving model validation in instability regimes. The experimental campaign combines full-field measurements obtained through digital image correlation with local strain data from strain gauges, adopting a back-to-back configuration to capture the strain reversal associated with global buckling. The experimental results are compared with nonlinear finite element simulations incorporating intralaminar damage based on Hashin’s failure criteria. A good agreement between the numerical and experimental results is observed in the pre-buckling and early post-buckling regimes. However, increasing discrepancies arise at higher load levels, mainly due to manufacturing imperfections and uncertainties in boundary conditions, which influence the onset and evolution of localized deformation. Statistical indicators are employed to quantitatively assess the correlation between the experimental and numerical responses. The analysis focuses on the key response parameters, including the load–displacement behaviour, out-of-plane displacements, strain evolution, and damage initiation, enabling a comprehensive comparison of experimental and numerical results. The results demonstrate the effectiveness of combining full-field and point-wise measurements for validating numerical models of composite structures. Furthermore, the study highlights the limitations of idealized modelling assumptions and provides insights into the sensitivity of CFRP structures to imperfections in post-buckling and failure regimes. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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25 pages, 10246 KB

Open AccessArticle

Development and Characterization of Active Pectin–Curdlan Biopolymer Films with Cannabigerol (CBG) Oil as Innovative Materials with Plant Metabolism–Stimulating Properties and Potential to Extend the Postharvest Shelf Life of Blackberries (Black Satin) Fruits

by Renata Dobrucka, Maja Paterska and Marcin Szymański

Polymers 2026, 18(7), 890; https://doi.org/10.3390/polym18070890 - 6 Apr 2026

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Abstract

In the present study, the physicochemical, mechanical, and functional properties of biodegradable pectin/cudlan gum polysaccharide films with CBG oil were evaluated. In these studies, the TS values for the films ranged from 8.50 MPa to 14.80 MPa. The EB values ranged from 33.06% [...] Read more.

In the present study, the physicochemical, mechanical, and functional properties of biodegradable pectin/cudlan gum polysaccharide films with CBG oil were evaluated. In these studies, the TS values for the films ranged from 8.50 MPa to 14.80 MPa. The EB values ranged from 33.06% to 39.07%. The WVTR ranged from 13.7 to 9.51 g/m² d. In all the films tested, the change in the L* parameter did not change significantly statistically (p ≥ 0.05). In films with low CBG content (0.125F, 0.25F, 0.35F), L* remained stable, which indicated their resistance to darkening. However, film 0.5F was an exception, as it showed a decrease in L*, suggesting darkening or photodegradation processes. CBG films reduced mold growth, water loss, color degradation, and anthocyanin content in stored fruit, especially films with a content of 0.125F–0.35F, while higher concentrations (0.5F–0.75F) could cause pro-oxidative effects. Soil application of the film showed that moderate CBG concentrations (0.25F–0.35F) increased the content of chlorophyll, carotenoids, and phenols, indicating biostimulating potential, while the highest concentrations could cause oxidative stress. At the highest CBG concentration (0.75F), the carotenoid content decreased to 0.054–0.113 mg·g⁻¹ FW. At higher concentrations of active substances in the film (0.5F and 0.75F), stabilization or a decrease in O₂•⁻ levels was observed, which may indicate the effective activation of protective mechanisms leading to the neutralization of excess free radicals. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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22 pages, 5903 KB

Open AccessArticle

Bound Rubber as a Transferable Structural Descriptor: Connecting MD-Derived Interfacial Scaling to Continuum Reinforcement Models

by Yancai Sun, Wenzhong Deng, Haoran Wang, Ranran Jian, Wenjuan Bai, Dianming Chu, Peiwu Hou and Yan He

Polymers 2026, 18(5), 565; https://doi.org/10.3390/polym18050565 - 26 Feb 2026

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Abstract

Filled elastomers often exhibit a low-frequency power-law storage modulus (G-prime), yet quantitative links between molecular interfacial structure and macroscopic reinforcement remain unresolved. This gap is addressed using a hierarchical multiscale framework that integrates coarse-grained molecular dynamics (MD) and dynamic mechanical analysis (DMA). Overall, [...] Read more.

Filled elastomers often exhibit a low-frequency power-law storage modulus (G-prime), yet quantitative links between molecular interfacial structure and macroscopic reinforcement remain unresolved. This gap is addressed using a hierarchical multiscale framework that integrates coarse-grained molecular dynamics (MD) and dynamic mechanical analysis (DMA). Overall, MD contributes transferable structural descriptors rather than direct macro-rheology prediction. MD simulations yield a bound-layer scaling relation for chain length

N = 50

in coarse-grained simulations serving as a structural probe. For EPDM master curves, the single-phase fractional Maxwell model is statistically preferred (Delta AICc > 147, n = 56), reflecting limited statistical power; larger datasets (e.g., PC/ABS, n = 952) favor the dual-phase formulation. For cross-scale prediction, an MD-derived effective-volume-fraction baseline (MAPE = 54.1%) provides a structural prior; the regime-partitioned bridge model absorbs relaxation physics not resolved at the MD scale, reducing error to 7.3% (blocked-CV MAPE = 9.5%, with a 2.3% fold-to-fold spread). Linear-viscoelastic constraints improve nonlinear PTT calibration, reducing die-swell error by 87%. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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21 pages, 2076 KB

Open AccessArticle

Synergistic Effects of Devulcanized Rubber, Polyethylene, and Fumed Silica on the Rheological and Structural Stability of Bitumen

by Akkenzhe Bussurmanova, Anar Akkenzheyeva, Viktors Haritonovs, Remo Merijs-Meri, Janis Zicans, Uzilkhan Yensegenova, Yerzhan Imanbayev, Yerbolat Ayapbergenov, Maira Turkmenbayeva, Murshida Aimova, Assiya Boranbayeva, Martynas Jankauskas and Romans Kornisovs

Polymers 2026, 18(2), 208; https://doi.org/10.3390/polym18020208 - 12 Jan 2026

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Abstract

This study examines the influence of virgin polyethylene (vPE), recycled polyethylene (rPE), and Aerosil (A) on the performance of bitumen binders modified with partially devulcanized rubber (DVR). The experimental program included morphology analysis, determination of devulcanization degree, dynamic viscosity measurements, shear stress–shear rate [...] Read more.

This study examines the influence of virgin polyethylene (vPE), recycled polyethylene (rPE), and Aerosil (A) on the performance of bitumen binders modified with partially devulcanized rubber (DVR). The experimental program included morphology analysis, determination of devulcanization degree, dynamic viscosity measurements, shear stress–shear rate analysis, load–displacement (F–Δl) testing, storage-stability evaluation, ring and ball softening point (R&B), penetration (P), and elastic recovery (ER) testing. The results show that DVR-rPE-modified bitumen binders exhibit 20–35% higher viscosity and up to 25% greater elongation at the break compared to DVR-vPE-modified bitumen systems, indicating more effective interaction with the bitumen matrix. The incorporation of Aerosil increased viscosity ca. 1.5–2 times for DVR-rPE and DVR-vPE-modified systems, respectively. Meanwhile, top and bottom differences in R&B decreased by a factor of 1.6–5 for DVR-rPE and DVR-vPE-containing composites, respectively, demonstrating significant enhancement in structural stability during storage. Mechanical testing further revealed that DVR-rPE + A binders absorbed 10–20% more deformation energy and consistently maintained ER values above 70–80%, corresponding to a higher elastic recovery grade at 25 °C. Overall, the DVR-rPE + A system provided the most balanced improvements in rheological, mechanical, and thermal properties, confirming its potential for use in high-performance, thermally stable, and environmentally sustainable bituminous materials for pavement applications. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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27 pages, 3785 KB

Open AccessArticle

Comprehensive Analysis of Chlorine-Induced Aging in High-Density Polyethylene: Insights into Structural, Thermal, and Mechanical Degradation Mechanisms

by Elena-Emilia Sirbu, Maria Tănase, Alin Diniță, Cătălina Călin, Gheorghe Brănoiu and Ionuț Banu

Polymers 2026, 18(1), 14; https://doi.org/10.3390/polym18010014 - 21 Dec 2025

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Abstract

This study investigates chlorine-induced aging of high-density polyethylene (HDPE) through a 3 × 3 factorial matrix combining three temperatures (20, 40, 60 °C) and three chlorine concentrations (5, 10, 20 ppm) over 45 days. Tensile tests revealed progressive embrittlement, with elongation at break [...] Read more.

This study investigates chlorine-induced aging of high-density polyethylene (HDPE) through a 3 × 3 factorial matrix combining three temperatures (20, 40, 60 °C) and three chlorine concentrations (5, 10, 20 ppm) over 45 days. Tensile tests revealed progressive embrittlement, with elongation at break decreasing sharply under severe aging; samples exposed to 60 °C and 20 ppm exhibited premature brittle failure despite peak stresses remaining near ~22 MPa. XRD results showed a reduction in crystallinity from 67.07% (reference) to 61.06–61.31% under the most aggressive conditions, accompanied by a decrease in crystallite size from 5.60 nm to 2.10–2.50 nm. FTIR analysis confirmed oxidation through increased carbonyl absorption at 1716 cm⁻¹ and new bands at 1608–1635 cm⁻¹. TGA revealed substantial thermal deterioration, with T5% falling from 450 °C (reference) to 327 °C at 60 °C/20 ppm, along with an additional degradation peak at 398 °C. DSC showed a melting temperature decrease from 136.32 °C to 131.67 °C and an increase in crystallinity from 41.07% (unexposed sample) to 59.19% (60 °C/20 ppm). Statistical analysis of the results established that degradation is governed by different dominant factors depending on the measured property: Chlorine concentration was found to be the dominant factor for XRD crystallinity and thermal decomposition T5%, confirming that surface structural damage and early molecular weight loss are driven primarily by chlorine-induced oxidation. Conversely, DSC crystallinity was governed primarily by temperature, reflecting thermally driven molecular reorganization within the bulk material. Overall, chlorine exposure, amplified by temperature, accelerates chemical oxidation, structural degradation, and mechanical embrittlement, reducing the long-term reliability of HDPE in chlorinated water systems. The findings provide critical data for predicting the service life and informing material selection for HDPE components used in high-temperature or high-chlorine water distribution systems. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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14 pages, 1825 KB

Open AccessArticle

Formulation and Characterization of PLGA Minocycline Microneedles for Enhanced Skin Deposition and Antibacterial Activity in Acne Treatment

by Juhaina M. Abu Ershaid, Suha M. Abudoleh, Dima N. Lafi and Nisreen A. Dahshan

Polymers 2025, 17(21), 2912; https://doi.org/10.3390/polym17212912 - 31 Oct 2025

Cited by 2 | Viewed by 1448

Abstract

Acne is a multifactorial skin condition characterized by an infection in the pilosebaceous units in the skin. Patients with acne suffer from comedones, papules, pustules and nodules or cysts in severe cases. These clinical features might cause disfigurmentation, depression, anxiety and significantly impact [...] Read more.

Acne is a multifactorial skin condition characterized by an infection in the pilosebaceous units in the skin. Patients with acne suffer from comedones, papules, pustules and nodules or cysts in severe cases. These clinical features might cause disfigurmentation, depression, anxiety and significantly impact the quality of life of patients. Systemic and continuous exposure of antibiotics put patients at risk of developing systemic toxicity, bacterial resistance and gut dysbiosis. Microneedles offer an innovative approach of providing targeted topical delivery of minocycline while insuring efficient permeation through skin layers. Methods: minocycline microneedles were formulated using casting method and characterized for insertion ability, mechanical strength, drug content, antibacterial activities, deposition and dissolution behavior using ex vivo full-thickness rat skin. Results: Insertion tests confirmed effective skin penetration and mechanical integrity with only 9.5% height reduction. Drug content was 673.06 ± 5.34 µg/array. Dissolution occurred within 2 min in skin, indicating user-friendly wear time. Ex vivo Franz diffusion studies showed 26% of the drug deposited into the skin, significantly higher (p = 0.0068) than the 18.3% that permeated through it. Antibacterial testing revealed strong activity against S. aureus, S. epidermidis, and C. acnes, with MIC values < 0.146 µg/mL and MBC values ranging from 9.375–18.75 µg/mL. Conclusions: The result of this research demonstrate that minocycline microneedles effectively deliver minocycline into the skin highlighting their potential as a safer and more efficient alternative for acne therapy. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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17 pages, 3116 KB

Open AccessArticle

Enhancement of Stability Towards Aging and Soil Degradation Rate of Plasticized Poly(lactic Acid) Composites Containing Ball-Milled Cellulose

by Roberta Capuano, Roberto Avolio, Rachele Castaldo, Mariacristina Cocca, Federico Olivieri, Gennaro Gentile and Maria Emanuela Errico

Polymers 2025, 17(15), 2127; https://doi.org/10.3390/polym17152127 - 1 Aug 2025

Cited by 1 | Viewed by 1012

Abstract

In this study, multicomponent PLA-based biocomposites were developed. In particular, both native fibrous cellulose and cellulose with modified morphology obtained through ball milling treatments were incorporated into the polyester matrix in combination with an oligomeric plasticizer, specifically a lactic acid oligomer (OLA). The [...] Read more.

In this study, multicomponent PLA-based biocomposites were developed. In particular, both native fibrous cellulose and cellulose with modified morphology obtained through ball milling treatments were incorporated into the polyester matrix in combination with an oligomeric plasticizer, specifically a lactic acid oligomer (OLA). The resulting materials were analyzed in terms of their morphology, thermal and mechanical properties over time, water vapor permeability, and degradation under soil burial conditions in comparison to neat PLA and unplasticized PLA/cellulose composites. The cellulose phase significantly affected the mechanical properties and enhanced their long-term stability, addressing a common limitation of PLA/plasticizer blends. Additionally, water vapor permeability increased in all composites. Finally, the ternary systems exhibited a significantly higher degradation rate in soil burial conditions compared to PLA, evidenced by larger weight loss and reduction in the molecular weight of the PLA phase. The degradation rate was notably influenced by the morphology of the cellulose phase. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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16 pages, 3399 KB

Open AccessArticle

Relationship Between Filler Type, Thermomechanical Properties, and Aging of RTV Silicone Foams

by Xavier M. Torres, John R. Stockdale, Adam Pacheco, Shelbie A. Legett, Lindsey B. Bezek, Bart Benedikt, Andrea Labouriau and Santosh Adhikari

Polymers 2025, 17(14), 1998; https://doi.org/10.3390/polym17141998 - 21 Jul 2025

Cited by 1 | Viewed by 1145

Abstract

Room-temperature vulcanizing (RTV) silicone foams are used in many industrial applications that require the material to perform over long time periods. However, mechanical properties tend to deteriorate when these foams age under a compressive load. The chemical aging is attributed to the presence [...] Read more.

Room-temperature vulcanizing (RTV) silicone foams are used in many industrial applications that require the material to perform over long time periods. However, mechanical properties tend to deteriorate when these foams age under a compressive load. The chemical aging is attributed to the presence of unreacted functional groups of the prepolymers, residues from acid, and catalytically active tin (II) species. Here, an optimized thermal treatment of an RTV foam that achieves completion of curing reactions and deactivation of reactive species is proposed. Foams that were thermally aged for three months under compressive load showed no signs of compression set, indicative of the effectiveness of the implemented post-curing approach. In addition, the effects of fillers (diatomaceous earth, fumed silica, and carbon nanofibers) on thermomechanical properties were investigated. Tensile strength, tear strength, and thermal conductivity increased when these fillers were added to the unfilled RTV formulation, with carbon nanofibers (CNFs) being the most effective filler. Rheological studies of RTV formulations indicated that 2.5 wt.% of CNFs is the upper limit that can be added to the RTV formulation. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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19 pages, 4384 KB

Open AccessArticle

Porous Osteoplastic Composite Materials Based on Alginate–Pectin Complexes and Cation-Substituted Hydroxyapatites

by Galina A. Davydova, Inna V. Fadeeva, Elena S. Trofimchuk, Irina I. Selezneva, Muhriddin T. Mahamadiev, Lenar I. Akhmetov, Daniel S. Yakovsky, Vadim P. Proskurin, Marco Fosca, Viktoriya G. Yankova, Julietta V. Rau and Vicentiu Saceleanu

Polymers 2025, 17(13), 1744; https://doi.org/10.3390/polym17131744 - 23 Jun 2025

Cited by 1 | Viewed by 1286

Abstract

Novel three-dimensional porous composites of alginate–pectin (A/P) with zinc- or manganese-substituted hydroxyapatites (A/P-ZnHA and A/P-MnHA) were synthesized via lyophilization and calcium cross-linking. Powder X-ray diffraction and infrared spectroscopy analyses confirmed single-phase apatite formation (crystallite sizes < 1 µm), with ZnHA exhibiting lattice contraction [...] Read more.

Novel three-dimensional porous composites of alginate–pectin (A/P) with zinc- or manganese-substituted hydroxyapatites (A/P-ZnHA and A/P-MnHA) were synthesized via lyophilization and calcium cross-linking. Powder X-ray diffraction and infrared spectroscopy analyses confirmed single-phase apatite formation (crystallite sizes < 1 µm), with ZnHA exhibiting lattice contraction (*c*-axis: 6.881 Å vs. 6.893 Å for HA). Mechanical testing revealed tunable properties: pristine A/P sponges exhibited an elastic modulus of 4.7 MPa and a tensile strength of 0.10 MPa, reduced by 30–70% by HA incorporation due to increased porosity (pore sizes: 112 ± 18 µm in the case of MnHA vs. 148 ± 23 µm-ZnHA). Swelling capacity increased 2.3–2.8-fold (125–155% vs. 55% for A/P), governed by polysaccharide interactions. Scanning electron microscopy investigation showed microstructural evolution from layered A/P (<100 µm) to tridimensional architectures with embedded mineral particles. The A/P-MnHA composites demonstrated minimal cytotoxicity for the NCTC cells and good viability of dental pulp stem cells, while A/P-ZnHA caused ≈20% metabolic suppression, attributed to hydrolysis-induced acidification. Antibacterial assays highlighted A/P-MnHA′s broad-spectrum efficacy against Gram-positive (Bacillus atrophaeus) and Gram-negative (Pseudomonas protegens) strains, whereas A/P-ZnHA targeted only the Gram-positive strain. The developed composite sponges combine cytocompatibility and antimicrobial activity, potentially advancing osteoplastic materials for bone regeneration and infection control in orthopedic/dental applications. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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30 pages, 3546 KB

Open AccessSystematic Review

Polymeric Materials in Biomedical Engineering: A Bibliometric Mapping

by Cristina Veres, Maria Tănase and Dan-Alexandru Szabo

Polymers 2025, 17(21), 2886; https://doi.org/10.3390/polym17212886 - 29 Oct 2025

Cited by 2 | Viewed by 1984

Abstract

This study offers an integrated synthesis of polymeric materials in biomedical engineering, revealing four major and interlinked research domains: tissue engineering and regenerative medicine, drug delivery and nanomedicine, wound healing and antimicrobial applications, and advanced fabrication through 3D/4D printing and bioprinting. Across these [...] Read more.

This study offers an integrated synthesis of polymeric materials in biomedical engineering, revealing four major and interlinked research domains: tissue engineering and regenerative medicine, drug delivery and nanomedicine, wound healing and antimicrobial applications, and advanced fabrication through 3D/4D printing and bioprinting. Across these areas, hydrogels, biodegradable composites, and stimuli-responsive polymers emerge as the most influential material classes. The analysis highlights substantial progress in extracellular matrix–mimetic scaffolds, smart drug delivery systems with controlled release, multifunctional wound dressings integrating antimicrobial and healing functions, and patient-specific constructs produced via additive manufacturing. Despite these advances, recurring challenges persist in long-term biocompatibility and safety, scalable and reproducible fabrication, and regulatory standardisation. The results point toward a convergence of bioactivity, manufacturability, and clinical translation, with hybrid natural–synthetic systems and personalised polymeric designs defining the next phase of biomedical polymer innovation. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis and Application)

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