Search Results (1,253)

The increasing generation of agricultural and industrial waste has created a growing need for sustainable materials that can reduce environmental burdens while maintaining desirable performance. This study explores the development of hybrid composites using pinecone waste and cottonseed waste generated during spinning operations as reinforcement materials in epoxy and PCL (polycaprolactone) matrices. Four composite formulations were produced and evaluated in terms of their physical, mechanical, thermal, morphological, and crystallographic characteristics. Density, water absorption, tensile, compressive, flexural, and thermal conductivity properties were measured using standard testing procedures. Surface morphology and fiber–matrix interactions were examined through scanning electron microscopy (SEM), while X-ray diffraction (XRD) was used to investigate the crystalline structure of the composites. The epoxy-based formulations exhibited superior tensile and flexural performance, reduced moisture uptake, and lower thermal conductivity, indicating their suitability for interior and semi-structural applications. In comparison, the PCL-based composites demonstrated higher compressive load resistance and greater deformation capability, suggesting potential use in biodegradable packaging and cushioning materials. SEM analysis revealed noticeable differences in filler distribution and interfacial characteristics among the formulations, whereas XRD confirmed the crystalline features associated with both the polymer matrices and lignocellulosic reinforcements. Overall, the results demonstrate a practical route for converting forestry residues and spinning-industry waste into functional composite materials, supporting waste valorization and resource-efficient material development. Full article

Magnesium alloys are used or considered for lightweight structures and biodegradable implants, but high electrochemical activity, limited wear resistance, and localized corrosion still limit their service reliability. Plasma electrolytic oxidation (PEO), also called micro-arc oxidation (MAO), forms an adherent ceramic scaffold. Discharge channels, interconnected pores, thermal cracks, and a mechanically weak outer layer mean that the as-formed coating is rarely a complete protective system. This review examines advanced PEO/MAO-based composite coatings through a process–structure–function lens and develops an application-oriented design framework. The discussion covers PEO/MAO process-window control, electrolyte and particle engineering, sol–gel and polymer sealing, layered double hydroxide/inhibitor systems, self-healing reservoirs, superhydrophobic and slippery interfaces, Ca-P/hydroxyapatite and polymer biofunctionalization, and duplex coatings for wear, electrical, and thermal functions. Emphasis is placed on how these modules regulate defect connectivity, mass transport, interfacial stability, damage response, tribocorrosion, and biodegradation, as well as on the evidence needed to support each claimed function. The analysis indicates that coating performance is governed not by multilayer complexity alone, but by the compatibility among the ceramic scaffold, functional module, dominant failure mode, and service-specific validation protocol. Chloride-exposed structures require durable pore sealing and active inhibition; wear-critical components require coupled corrosion–wear assessment; and biodegradable implants require a degradation window that balances corrosion moderation, cytocompatibility, biofunctionality, and residual mechanical integrity. Remaining challenges include interfacial durability, finite inhibitor reservoirs, wetting-state instability, process reproducibility, scale-up, and life-cycle impacts. The proposed process maps and validation criteria are intended to support modular, testable, and application-specific PEO/MAO surface systems for magnesium alloys. Full article

Polymer-based sandwich structures have garnered significant interest as energy-absorbing protective materials. However, common damage modes in composite sandwich panels include matrix cracking, delamination, core crushing or core fracture, and debonding between the face sheets and the core. Among these, face–core debonding is one of the most prevalent failure mechanisms. This paper investigates a sandwich configuration designed to enhance blast resistance by incorporating a self-adhesive, stiffened polyimide foam (ASPI) into a steel–foam–steel architecture. The thermogravimetric analysis exhibits that ASPI foam obtained excellent thermal stability, and the residual mass retention at 800 °C was more than 36.2%. Experimental results show that at scaled distances of 1.077 m/kg^1/3 and 1.292 m/kg^1/3, the ASPI foam-based sandwich panels exhibited mid-span displacements as low as 8.5 mm and 6.7 mm, respectively. Under a scaled distance of 1.077 m/kg^1/3, the mid-span displacement of the ASPI foam-based sandwich structure decreased from 15.0 mm to 8.5 mm, representing a 43.3% reduction compared with that of the neat polyimide foam-based sandwich structure. Moreover, compared with neat PI foam, the ASPI foam exhibited superior adhesion to steel face sheets, and no interfacial debonding was observed after blast loading. To further elucidate the underlying damage mechanisms under blast loading, a well-validated finite element model was developed and employed. Complementary scanning electron microscopy (SEM) analyses were conducted to examine the microstructural morphology of the ASPI foam core’s cross-section and surface after blast exposure. This study presents an investigation of a lightweight, self-adhesive, high-thermal stability, blast-resistant polymer-based composite foam. Full article

Oral administration of narrow therapeutic index anticoagulants like phenprocoumon (PHP) necessitates careful control of the kinetic release of the drug to avoid dose dumping and severe haemorrhagic effects. This study was carried out to prepare and characterize novel PHP delivery systems based on κ-carrageenan hydrogels, exploring the importance of potassium ion (K⁺) stabilization in controlling the release process. FT-IR, TG/DTG, and in vitro release studies were employed in combination with a new validated RP-HPLC assay. FT-IR and thermal analysis results showed that PHP is physically encapsulated into the polysaccharide matrix, where there are no chemical incompatibilities between them. Furthermore, potassium ions increase the stability and heat resistance of the polymer network. However, when K⁺ was considered for modelling the kinetic release using the Korsmeyer–Peppas equation, it was observed that PHP is released from the K⁺ stabilized matrix in a relaxation dominated diffusion-controlled transport. Ionic cross-linking effectively reduces the initial burst effect, demonstrating that these matrices are promising vehicles for the sustained delivery of phenprocoumon. Full article

Polyimide (PI) exhibits outstanding thermal stability and mechanical rigidity; however, their inherently rigid backbones lead to intrinsic brittleness, poor fracture toughness, and inferior impact resistance. Conversely, polyurea (PUA) features excellent elasticity, tunable soft–hard segment architectures, and a favorable balance of tensile strength and elongation at break. Herein, we systematically investigate the thermal and mechanical properties of 12 distinct PI, PUA, and PI-PUA copolymer systems via all-atom molecular dynamics simulations. Simulations demonstrate that rigid aromatic moieties significantly increase T_g and elastic modulus, while flexible hexamethylene diisocyanate (HDI) yields the highest elastic modulus via dense hydrogen-bond networks despite lowering T_g. Fluorine substitution effectively increases fractional free volume and moderately reduces T_g. Toughness is evaluated by K/G. System L with bulky phthalide side groups exhibits the highest K/G of 3.24, suggesting potential for improved plastic deformability as a preliminary screening indicator. In contrast, HDI-containing systems E and H show the lowest K/G ratios, as strong interchain hydrogen bonding severely restricts segmental slippage and induces brittle fracture. PI-PUA copolymerization proves to be an effective strategy to balance stiffness and toughness over a broad performance range. This work establishes structure–property correlations for PI-PUA systems, offering molecular-level insights for the rational design of advanced high-performance polymers, which require further experimental validation. Full article

In recent years, the quest for advanced materials has intensified, driving the exploration of innovative coating systems to enhance material properties. Polymeric materials, renowned for their adaptability, have found extensive use across various industries. However, their inherent limitations in mechanical strength, wear resistance, and thermal stability have prompted researchers to seek enhancement avenues. Hybrid polymeric–metallic coatings have emerged as a promising solution, employing thermal spray techniques to metalize polymeric substrates. This amalgamation utilizes the versatility of thermal spraying methods, ranging from cold spraying, flame spraying, arc spraying, to plasma spraying, to achieve robust adhesion between metal and polymer layers. These techniques yield durable composite structures, fortifying surfaces against corrosion and wear while enabling dimensional restoration. Cold spraying, in particular, stands out among thermal spray methods due to its effectiveness in metalizing various materials. This comprehensive review delves into recent advancements in hybrid polymeric–metallic coatings via thermal spray processes. Emphasis is placed on analyzing critical factors influencing coating properties, including various thermal spray parameters. Furthermore, the paper scrutinizes the challenges and future potentials inherent in thermal spray techniques, with a focused exploration of cold spray technology. Understanding these methodologies is pivotal for optimizing the design and durability of structural materials made of polymers or composites. Full article

Conventional polyolefin battery separators are limited by inherent deficiencies in thermal stability, electrolyte wettability, and environmental sustainability, which collectively hinder the advancement of high-energy-density energy storage systems. In this context, biomass macromolecular materials, including cellulose, chitin/chitosan, and lignin, have emerged as promising candidates for next-generation separators owing to their environmental benefits, exceptional hydrophilicity, and superior thermal resistance. This review systematically evaluates the molecular characteristics of these three biomass systems, alongside core gel-state processing and network-forming processes such as electrospinning, solution casting, nonwoven technology, and hydrogel-assisted film formation. It further highlights their cutting-edge applications in lithium-ion, lithium–sulfur, zinc-ion, and solid-state batteries, emphasizing their behavior as polymer gel electrolytes and gel-derived structural matrices. To overcome key challenges associated with mechanical robustness, interfacial compatibility, and network uniformity, advanced modification strategies are critically discussed, including surface chemical functionalization, multicomponent hybrid composite formulation, and rational three-dimensional structural engineering. Overall, current research evidence demonstrates that rationally designed biomass-based gel networks and membranes can effectively suppress metal dendrite growth, immobilize soluble polysulfide intermediates via supramolecular interactions, and reduce interfacial impedance in solid-state systems, thereby offering a viable pathway toward safer, more sustainable, and commercially competitive high-energy-density batteries. Full article

Collagen-based biomaterials possess many advantages, such as low immunogenicity, biodegradability, biocompatibility, hydrophilicity, and ease of processability. Nevertheless, natural collagen has inherent limitations as an in vivo scaffold, including insufficient mechanical strength, low thermal stability, and low resistance to enzymatic degradation. To overcome these drawbacks, various approaches have been studied, such as mixing collagen with other biopolymers or inducing physical and chemical crosslinking. However, using non-biologically derived polymers or crosslinking agents carries the risk of persistence in the body, potentially causing cytotoxicity. Considering this, recent studies have reported that the molecular flexibility of collagen networks can be improved by activating the carboxyl groups of collagen chains using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide and then crosslinking them through amide bonding with the amino groups present in the collagen chains, or by adding free L-lysine to induce a crosslinking reaction. When the carboxyl groups of collagen are activated and form covalent bonds with amino groups, native ionic interactions (e.g., salt bridges) may be reduced, which can potentially influence the stability of its inherent higher-order structure. In this study, we proposed a selective amine-targeted cross-linking strategy designed to minimize modification of collagen carboxyl groups while enhancing mechanical properties and cellular compatibility. First, free L-glutamic acid was pre-activated to cross-link collagen chains through amide bonds with the amino groups of L-lysine residues, thereby providing a cross-linking pathway intended to reduce the involvement of collagen carboxyl groups in the reaction. By controlling the concentration of L-glutamic acid, the cross-linking rate of the collagen could be controlled within a range of 10.26% to 25.02%. All cross-linked collagen scaffolds exhibited higher tensile strength compared to non-cross-linked scaffolds. Although the scaffolds with a high cross-linking rate (25.02%) displayed excellent mechanical properties, their cellular compatibility was relatively low. Conversely, collagen scaffolds with cross-linking rates of 10.26% and 14.43% demonstrated excellent mechanical properties and very high cellular compatibility, suggesting potential applications in the fields of biomedicine and tissue engineering. The present findings are consistent with the proposed selective cross-linking strategy; however, direct experimental verification of collagen carboxyl-group preservation will require complementary analytical studies. Full article

The growing demand for sustainable food packaging materials has accelerated the development of biodegradable alternatives to conventional petroleum-based plastic. This study investigates the reinforcement of electroblown gelatin/polyvinyl alcohol (G-PVA) nanofibrous mats with kombucha-derived bacterial cellulose nanowhiskers (BCNWs) to enhance their mechanical, thermal, and surface properties while promoting the valorization of symbiotic culture of bacteria and yeast (SCOBY) waste. BCNWs were incorporated into the G-PVA matrix at different loadings, and the resulting nanocomposites were characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), tensile testing, and water contact angle measurements. The addition of BCNW significantly improved the tensile strength of the nanofibrous mats, with a maximum increase about 120% compared with neat G-PVA nanofibers. SEM images revealed uniform, bead-free fiber structures at appropriate BCNW concentrations, while FTIR and XRD analyses confirmed effective interactions between the nanowhiskers and the polymer matrix. TGA results indicated enhanced thermal stability at moderate BCNW loadings, whereas excessive BCNW content promoted agglomeration and reduced thermal resistance. Furthermore, the incorporation of BCNWs increased the water contact angle to 144.11 ± 1.45°, demonstrating improved surface hydrophobicity. Overall, kombucha-derived BCNWs effectively reinforced electroblown G-PVA nanofibers, producing biodegradable nanocomposite mats with improved performance and strong potential for sustainable food packaging applications. Full article

Carbon fibre-reinforced polymer (CFRP) composites represent promising lightweight materials for automotive powertrain systems, where increasing demands for weight reduction, energy efficiency, and emission reduction are driving the replacement of conventional metallic components. However, automotive powertrain environments expose CFRP materials to elevated temperatures, cyclic mechanical loading, chemical exposure, and tribological interactions, creating complex degradation conditions that significantly influence long-term durability and reliability. This review systematically analyzes CFRP composites for automotive powertrain applications, focusing on the relationship between operational requirements, material selection, reinforcement architecture, manufacturing technologies, and degradation mechanisms. High-performance thermoplastic systems such as CF/PEEK, CF/PPS, and CF/PEKK are critically compared with conventional thermoset composites. CF/PEEK systems demonstrate superior thermomechanical stability, maintaining significant mechanical performance at temperatures approaching 250 °C and tensile strengths of approximately 1400–1600 MPa, whereas CF/PPS composites provide a more economically efficient compromise between thermal resistance, chemical stability, manufacturability, and recyclability for medium-temperature applications. The review further analyzes dominant degradation mechanisms, including creep deformation, fatigue damage, delamination, fibre–matrix interface degradation, and tribological wear. CFRP degradation is shown to result from the interaction of multiple coupled mechanisms rather than from isolated material failure modes. Tribological wear rates typically range from 10⁻⁶ to 10⁻⁵ mm³/(N·m), while creep–fatigue interactions may reduce component lifetime by up to 40–60% under combined thermomechanical loading. Advanced design strategies, including fibre orientation optimization, laminate architecture tailoring, thickness gradation, and hybrid metal–composite structures, are evaluated together with major manufacturing technologies such as injection moulding, compression moulding, overmoulding, automated fibre placement, and additive manufacturing. The presented review establishes an integrated framework linking material systems, operating conditions, manufacturing processes, and durability requirements for automotive powertrain applications. The analysis demonstrates that no universal CFRP system exists for all powertrain components and that optimal material selection requires balancing thermal stability, fatigue resistance, tribological performance, manufacturability, recyclability, and economic constraints according to the specific operating conditions of each component category. Full article

Proton-exchange membranes are crucial for water electrolyzers and fuel cells, but their performance declines under low humidity due to dehydration. Existing reviews mainly list experimental results without analyzing the mechanisms of proton conductivity stabilization. This review systematically summarizes approaches to enhance moisture-independent proton conductivity and evaluates their prospects. Key factors governing conductivity include microstructure, sulfonic group concentration, and hydration level. Stability under dry conditions depends on water retention and thermal resistance. Main strategies involve hybrid composite membranes, ionomer structure control via pre-treatments, and novel proton-conducting polymers. Promising directions include oriented channel structures, MOFs, and graphene-based materials. The stabilization mechanism relies on retaining water through hydrophilic additives that form stable hydrates, enabling proton transport even under harsh conditions (up to 120 °C and 50% RH, per US DOE targets). Among Nafion alternatives, sulfonated aromatic polymers and phosphoric-acid-doped polybenzimidazole demonstrate good performance at elevated temperatures (100–200 °C), though durability remains a challenge for the latter. Despite ongoing research, Nafion-based composites still offer one of the best overall balances of conductivity, stability, and processability. A significant research gap persists: long-term membrane performance is poorly studied, and many additives degrade over time or block proton transport sites due to ion exchange with metal cations. Full article

Intumescent coatings are widely used to enhance the fire resistance of structural steel. In contrast to traditional fire protection methods, this novel flexible intumescent protection offers several key advantages: universal compatibility with other coatings (via non-contact wrapping), resistance to extreme temperatures (−60 °C to +90 °C), all-weather usability, and suitability for light-gauge cold-formed thin-walled steel structures. This paper describes the development and investigation of these fire-protective, flexible intumescent coatings based on eco-friendly binders (silicone polymers and acrylic resins) with varying intercalated graphite (IG) content from 0% to 40%. An IG content of 25–40% enables a steel I-section with a section factor of 294 mm⁻¹ to reach its limit state at 44 min (compared to 15 min for unprotected steel). Fire tests on steel beams with a section factor of 172 mm⁻¹ demonstrated that samples reached the deflection limit state at the 64th and 66th minutes, respectively. Thermogravimetric analysis (TGA) was used to determine the temperature ranges for the thermal decomposition and expansion of the IG. Mechanical property studies revealed the influence of IG on the elastic modulus and tensile strength. Accelerated climatic testing in moderately cold conditions and salt spray chamber tests confirmed that the intumescent roll coating has no negative impact on the steel substrates. Full article

Thermal kinematics in two-layer systems, analogous to those employed in plain bearings, are investigated. The systems are based on a PEEK/CF30 composite, considered an established alternative to traditional babbitt alloys. Experimental modelling of transient and quasi-steady-state heat transfer regimes was performed on a test bench implementing a one-dimensional heat conduction model within multi-layered media. Samples included babbitt alloy and polymer coatings with thicknesses of 0.40, 0.46, and 1.92 mm. A phenomenological model of heat transfer regimes is proposed, encompassing five sequential phases that represent a complete operating cycle of plain bearing temperature traces. The observed constants of temperature deviations and phase lags are discussed, including their application as instrumental invariants. It was established that reducing the antifriction layer thickness to 0.4 mm significantly lowers its thermal resistance and decreases the time lag by a factor of 5–8. This brings the system response time close to values characteristic of classical babbitt alloys. It is demonstrated that in steady-state hydrodynamic friction regimes, the temperature deviation for thin layers is less than 1 °C, obviating the necessity for algorithmic data compensation. The findings confirm the safety of using polymer materials as the working layer in plain bearings. Despite their lower thermal conductivity and increased time lag, the composites’ high thermal stability margin comfortably compensates for potential temperature deviations, ensuring equipment reliability and safety. Full article

Bio-based packaging is receiving increasing attention due to the environmental impact of fossil-based plastics. However, its practical implementation requires further evidence on material processing and functional performance. This study evaluated the thermal properties of expanded polylactic acid (E-PLA) prototypes blended with raw, minimally processed agroforestry residues. Specifically, spruce bark and grape stalks were used as waste wood fibers. This study focused primarily on the thermal characterization of the materials by measuring thermal conductivity and resistance. To evaluate the distribution of the two fractions (polymer and fibrous), samples were created with various volumetric ratios between the parts. Simultaneous pressure and microwave heating of the sample were used to stabilize the material. To characterize the raw materials used in this study, bulk density and moisture content were measured. To characterize the mixed materials samples, thermal conductivity and resistance, bulk density, and pressure were measured. To investigate the variables that influence thermal characteristics, statistical analyses such as regression models, ANCOVA, and Spearman correlation were applied. These analyses showed that increasing the biofiber content significantly reduced thermal resistance and increased thermal conductivity. However, negligible effects were observed for the type of fiber used and the duration of the heat treatment. These results describe the thermal properties of blends containing E-PLA and agroforestry residues. The results also show a marked effect of the biofiber content on thermal performance. This study does not provide a comprehensive characterization of the new materials, as it focuses on the prototyping methodology and the laboratory-scale production feasibility of E-PLA/agroforestry-residue prototypes. Full article

The global transition toward plant-based diets has driven the inclusion and legumes as primary sources of proteins and micronutrients. However, the raw whole seed hosts complex matrices of antinutritional factors and crystalline starch arrangements that limit proteolytic digestibility, chelate essential minerals, and induce accelerated postprandial glycemic responses. Conventional culinary and thermal treatments applied in isolation are frequently insufficient to disrupt the physicochemical matrix of the seeds, leaving critical gaps regarding how to sustainably optimize mineral bioaccessibility and convert water-soluble starches into stable slowly digestible fractions. This scoping review synthesizes analytical evidence demonstrating that targeted fermentative bioprocessing acts as a microstructural modulator. However, these biochemical outcomes are not unidirectional; the expansion of nutritional value is strictly governed by a complex interplay of substrate properties, process moisture, pH adjustments, and thermal pretreatments in plant defense frameworks and spatially reorganizing starch polymers. Microbial organic acid production and the mechanical penetration of fungal hyphae promote a 90–100% degradation and elimination of phytates and condensed tannins, eliminating non-digestible galacto-oligosaccharides and inactivating trypsin inhibitors. These mechanisms optimize phytate-to-mineral molar ratios, doubling the bioaccessibility of iron, zinc, and calcium in the digestive aqueous phases, while microbial beta-glucosidase expression bioconverts conjugated glycosides into free aglycones with high antioxidant activity. Simultaneously, the induction of molecular retrogradation drives continuous increases in the resistant starch fraction, inducing significant reductions in the hydrolysis index and lowering the predictive glycemic index to low thresholds. These findings consolidate controlled fermentation as a viable biotechnological intervention, providing structural guidelines for the rational design of functional foods, biofortified baked goods, and vegan beverages with high digestive tolerance. Full article