Search Results (3,333)

This article presents an investigation of the thermomechanical properties of silicone elastomer-based polymer composites modified with carbon nanotubes (CNTs) and mixed fillers (CNTs, bronze, graphite). The primary technique employed was the composite piezoelectric oscillator (CPO) method at approximately 100 kHz. This approach enabled precise measurements of the polymers’ forced oscillation frequency and logarithmic damping decrement (internal friction) across a wide temperature range (80–300 K). The application of this method is novel for this specific class of materials. Scanning electron microscopy confirmed the uniform distribution of the fillers within the polymer matrix. Differential scanning calorimetry (DSC) showed that the fillers modify the thermal stability of the composite. The systematic decrease in the enthalpy of the endothermic decomposition peak suggests a retardation of degradation kinetics, most likely due to a barrier effect of the filler network. Electrical measurements revealed a distinct contrast: the hybrid composite exhibited a frequency-independent conductivity plateau (~1.8 × 10⁻¹ S/m), confirming a robust percolating network, unlike the strong frequency dependence observed for the CNT-only composite. Research shows that the fillers effectively suppress relaxation processes linked to crystallization (205–215 K) and glass transition (165–170 K), as evidenced by a significant reduction in the amplitude of the corresponding internal friction peaks. The most pronounced effect was observed in the composite with mixed fillers, attributable to a synergistic effect between constituents. Furthermore, amplitude-dependent internal friction was found to occur predominantly below the glass transition temperature. The primary objective of the present study is to investigate the dynamic mechanical and damping behavior of CNT-filled silicone composites with mixed fillers under high-frequency loading, using the CPO method. These findings demonstrate the potential for tailoring the stiffness and damping characteristics of these composites for advanced applications in soft robotics and portable electronics. Full article

Natural-fiber biocomposites are increasingly viewed as promising materials for sustainable engineering. However, their broader adoption remains constrained by coupled challenges related to interfacial compatibility, moisture sensitivity, environmental durability, processing limitations, and end-of-life trade-offs. Rather than treating fiber selection, matrix chemistry, processing routes, durability, and sustainability as independent considerations, this review emphasizes their interdependence through the fiber–matrix interface, which governs stress transfer, moisture transport, and long-term property evolution. It provides a comprehensive and integrative analysis of natural-fiber–reinforced polymer composites, encompassing plant-, animal-, and emerging bio-derived reinforcements combined with bio-based, biodegradable, and selected synthetic matrices. Comparative analysis across the literature demonstrates that interfacial engineering consistently dominates mechanical performance, moisture resistance, and property retention, while mediating trade-offs among stiffness, toughness, recyclability, and biodegradability. Moisture transport and environmental ageing are examined using thermodynamic and diffusion-controlled frameworks that link fiber chemistry, interfacial energetics, swelling, and debonding to performance degradation. Fire behavior and flame-retardant strategies are reviewed with attention to heat-release control and their implications for durability and circularity. Processing routes, including extrusion, injection molding, compression molding, resin transfer molding, and additive manufacturing, are assessed with respect to fiber dispersion, thermal stability, scalability, and compatibility with bio-based systems. By integrating structure–property relationships, processing science, durability mechanisms, and sustainability considerations, this review clarifies how natural-fiber biocomposites can be designed to achieve balanced performance, environmental stability, and circular life-cycle behavior, thereby providing guidance for the development of systems suitable for near-term engineering applications. Full article

This study investigated the properties of red algae (RA) biocomposite films reinforced with natural sisal fibers and plasticized with glycerol. The polymer was extracted from locally sourced red seaweed and combined sisal fibers at varying fiber loadings (0–45 wt%) using the doctor blading technique. Composite films were analyzed using a variety of methods to evaluate the chemical composition, thermal behavior and mechanical performance. Infrared spectroscopy confirmed the presence of kappa-carrageenan as the dominant polysaccharide in the RA matrix, whereas elemental analysis verified the dilution of sulfur content and enrichment of carbon with increasing fiber incorporation. Thermal stability increased with fiber loading, peaking at 30 wt% sisal fiber before decreasing slightly at 45 wt% due to poor fiber dispersion. Mechanical testing demonstrated an optimal balance between strength and flexibility at 30 wt% sisal fiber, with a 37% increase in strength compared to the pure RA film. Overall, the findings demonstrate that sisal fiber reinforcement enhances the structural integrity and stability of RA-based films, supporting their potential as biodegradable alternatives to petroleum-based plastics. Full article

Poly(3-hydroxybutyrate) (P3HB) was used to produce biocompatible composites with hypromellose as an additive. The study aimed to assess their biological and mechanical properties, as well as specific thermal parameters and phase content. Differential scanning calorimetry was applied to analyze the phase transitions of both biocomposites and the polymer matrix. Furthermore, the thermal parameters—encompassing both non-equilibrium and equilibrium states—of the biocomposites and unfilled P3HB were evaluated according to their thermal history. Using equilibrium parameters such as the heat of fusion for fully crystalline materials and the heat capacity change at the glass transition for fully amorphous composites, we estimated the degrees of crystallinity as well as the mobile and rigid amorphous fractions. Adding hypromellose to the P3HB matrix reduced crystallinity compared to the unfilled material. At the same time, an increase in the amorphous phase was observed. It was also discovered that the rigid amorphous fraction exists solely in biocomposites containing 2% by mass of filler. Thermogravimetric analysis showed that the thermal stability of all biocomposites surpasses that of unfilled P3HB. Adding an extra 1% filler by mass raises the degradation temperature by about 37 °C compared to unfilled P3HB. The immunosafety of the tested biocomposites, with very low or no endotoxin contamination, was confirmed in accordance with Food and Drug Administration and European Medicines Agency guidelines. The study clearly demonstrates the influence of the filler in the P3HB matrix on various structural, thermal, mechanical, and biological properties of the prepared biocomposites. Full article

This study explores novel silica gel/sulfonated polymer composite coatings for enhanced thermal management in electric vehicles via sorption technology. Leveraging the cost-effectiveness of silica gel as a filler and a readily available, water vapor-permeable sulfonated polymer as the matrix, we developed and characterized these materials. Mechanical assessments revealed varied performance: coatings with lower silica gel content (80 and 85 wt%) demonstrated suitable scratch resistance (damage width ~1100 µm at 1300 g load) and superior impact resistance (damage diameter ~2.4 mm). Pull-off adhesion strengths for these batches were 1.26 MPa and 1.36 MPa, respectively, though higher filler loading (90 and 95 wt%) led to a ~30% reduction and a shift to cohesive failure for high-filler-content batches. Thermogravimetric analysis confirmed thermal stability up to 280 °C. Adsorption studies revealed that the composite coating with 95 wt% of silica gel achieved the highest water uptake (just under 30 wt%), with all batches exhibiting capacities comparable to commercial adsorbents. This comprehensive characterization confirms that these composites offer a compelling balance of mechanical robustness, reliable adhesion, and high adsorption efficiency, positioning them as promising, cost-effective solutions for EV thermal management. Full article

This article proposes a novel preparation method for seawater-based low-alkalinity activated phosphogypsum (PG) cement, aimed at enhancing the performance of multi-waste binder systems using the highly ionic environment of seawater while addressing the cost and alkalinity issues associated with traditional high-alkalinity activators. The effects of partial replacement of ground granulated blast furnace slag (GGBS) with PG (0–15%) and fly ash (FA, 20–50%) on the setting time, rheological properties, microstructure, and compressive strength of seawater-based slurries were investigated. Compared to the control group (pure slag), the samples with a synergistic ratio of 5% PG and 35% FA had a mean compressive strength exceeding 60 MPa at 28 days, comparable to that of the control group, with a significant improvement in flowability. The results demonstrate that the proposed preparation method alters the hydration kinetics of alkali-activated GGBS cement and significantly improves the early and later compressive strength of hydrated samples. In the early hydration phase, seawater ions effectively promoted the rapid nucleation and growth of ettringite (AFt) crystals. The low-alkalinity composite activator induced the formation of a substantial amount of C-(A)-S-H gel. In the later stages of hydration, needle-like AFt crystals intertwined with the gel matrix, further densifying the microstructure. The enhancement of the polymer’s performance is primarily attributable to the key “synergistic enhancement effect” between seawater ions and the low-alkalinity environment. This interaction optimizes the formation pathways of key hydration products and refines the pore structure, providing a solid theoretical foundation for the low-carbon, high-efficiency utilization of PG in marine engineering materials. Full article

Vacuum infusion experiments were conducted to characterize the elastic recovery and thickness effect in the vacuum infusion molding process (VIMP). The results indicate that both the local fluid pressure and the part thickness increment increase with flow propagation until filling completion, and subsequently decrease during the post-filling stage. The maximum thickness increment increases with the number of reinforcement layers, while the thickness-increment rate decreases due to the enhanced compliance of the reinforcement. Specifically, for reinforcements with 10, 20, and 30 layers under in-plane 1D (One-Dimensional) flow, the thickness-increment rates are 4.97%, 4.74%, and 3.86%, respectively. In out-plane 1D flow, a distinct progressive three-stage thickness growth is observed, with corresponding increment rates of 43.7%, 23.0%, and 15.8% for 10, 20, and 30 layers, highlighting a significantly more pronounced effect. In contrast, for both coupled seepage-flow configurations (A and B), the thickness-increment rate shows no significant variation with layer number and remains consistently around 6%. This suggests that the thickness effect is offset by the coupled seepage-flow interaction of in-plane, out-plane, and distribution medium (DM) flows. It can be concluded that elastic recovery decreases with increasing part thickness. The thickness effect exerts a positive influence on the vacuum infusion molding of large-scale (thick-section) composite structures. Both elastic recovery and thickness effect are closely related to the injection mode (process strategy), with the effect in out-plane 1D flow being significantly greater than that in in-plane flow and coupled seepage flow. Full article

This study systematically investigates the influence of short carbon-fiber (SCF) content on the mechanical, thermal, and tribological properties of self-lubricating polyphenylene sulfide (PPS) composites filled with PTFE and MoS₂, addressing the critical need for high-wear resistance in Carbon-Fiber-Reinforced Thermoplastic (CFRTP) structural applications. The results identified 10 wt% SCF as the optimal content that achieved the best balance between load-bearing capacity and friction performance. The coefficient of friction μ and wear amount were reduced by 29.28% and 29.29%, respectively, compared to the PPS/PTFE/MoS₂ composite material without SCF, and by 14.67% and 20.75%, respectively, compared to the material with excessive SCF filling (20 wt%). Finite-Element Analysis-Representative Volume Element (FEA-RVE) reveals the mechanism by which excessive content of SCF at the microscopic level leads to a slight decrease in mechanical properties. Critically, the tribological performance exhibited a discrepancy with bulk mechanical properties: above 15 wt% SCF, the wear rate worsened despite high mechanical strength, revealing that increased fiber agglomeration and micro-abrasion effects were the primary causes of performance deterioration. Further in-depth XPS analysis revealed a synergistic lubrication mechanism: In the optimal sample, an ultra-dense PTFE transfer film was formed to mask the underlying MoS₂. This masking, coupled with the high surface activity of MoO₃ particles leads to stronger physicochemical interactions with the polymer matrix, ensures the exceptional durability and stability of the tribo-film. This research establishes a complete structure–performance relationship by integrating mechanical, thermal, and tribo–chemical mechanisms, offering critical theoretical guidance for the design of next-generation high-performance self-lubricating CFRTPs. Full article

Marine bioactive substances exhibit structural diversity and function-specific properties, attracting considerable interest in their potential applications in targeted nutritional delivery to the gut and microbiota regulation. These bioactive components, sourced from seaweed, marine crustaceans, and microorganisms, including polysaccharides, polyphenols, and lipids, demonstrate exceptional biocompatibility and specific recognition capabilities. They serve as an optimal carrier matrix and functional core for developing an efficient, precision-targeted intestinal nutrition delivery system. Research findings demonstrate that optimization via innovative delivery technologies, including nanoencapsulation and polymer microsphere encapsulation, enables marine bioactive substances to navigate various physiological barriers in the gastrointestinal tract effectively. This facilitates targeted, sustained release of nutritional components and enhances bioavailability. Simultaneously, these substances may relieve dysbiosis by modulating the composition of the gut microbiota and the quantity and activity of specific metabolic products, thereby reinforcing intestinal barrier integrity. This narrative review systematically examines the sources and functional attributes of marine bioactive compounds, emphasizing their application strategies in developing targeted delivery systems for the gut and their regulatory effects on gut microbiota. It concludes by delineating future research directions in this field, particularly in optimizing carrier functionalities and clarifying action mechanisms. Full article

A multiscale approach to calculating the effective elastic properties of a composite material with a fibrous filler and a polymer matrix is presented. Modeling at various scales is performed using a unified algorithmic scheme, solving Cauchy problems for systems of ordinary differential equations. At the atomic level, molecular dynamics modeling is used to calculate the elastic constant tensor of the polymer material. At the mesoscale, the author’s discrete element method is applied to calculate the effective elastic properties of the composite material. The method was tested on problems with regular fiber placement with symmetry, which have an analytical solution. The capabilities of the proposed approach are demonstrated using defect composite homogenization problems, where symmetry is broken. Fiber cracking and matrix–fiber debonding are considered. Full article

Lignin, an abundant and renewable biopolymer, holds significant potential for asphalt modification owing to its unique aromatic structure and reactive functional groups. This review summarizes the main lignin preparation routes and key physicochemical attributes and assesses its applicability for enhancing asphalt performance. The physical incorporation of lignin strengthens the asphalt matrix, improving its viscoelastic properties and resistance to oxidative degradation. These enhancements are mainly attributed to the cross-linking effect of lignin’s polymer chains and the antioxidant capacity of its phenolic hydroxyl groups, which act as free-radical scavengers. At the mixture level, lignin-modified asphalt (LMA) exhibits improved aggregate bonding, leading to enhanced dynamic stability, fatigue resistance, and moisture resilience. Nevertheless, excessive lignin content can have a negative impact on low-temperature ductility and fatigue resistance at intermediate temperatures. This necessitates careful dosage optimization or composite modification with softeners or flexible fibers. Mechanistically, lignin disperses within the asphalt, where its polar groups adsorb onto lighter components to boost high-temperature performance, while its strong interaction with asphaltenes alleviates water-induced damage. Furthermore, life cycle assessment (LCA) studies indicate that lignin integration can substantially reduce or even offset greenhouse gas emissions through bio-based carbon storage. However, the magnitude of the benefit is highly sensitive to lignin production routes, allocation rules, and recycling scenarios. Although the laboratory research results are encouraging, there is a lack of large-scale road tests on LMA. There is also a lack of systematic research on the specific mechanism of how it interacts with asphalt components and changes the asphalt structure at the molecular level. In the future, long-term service-road engineering tests can be designed and implemented to verify the comprehensive performance of LMA under different climates and traffic grades. By using molecular dynamics simulation technology, a complex molecular model containing the four major components of asphalt and lignin can be constructed to study their interaction mechanism at the microscopic level. Full article

The pursuit of alternatives to nonrenewable materials has stimulated the development of sustainable materials with improved performance, particularly polymer composites reinforced with plant-based fibers. In this study, eucalyptus fibers were thermally treated and evaluated as eco-friendly reinforcements for polyester composites, aiming to enhance their physical and mechanical properties. The fibers were subjected to heat treatments between 140 and 230 °C in a Macro-ATG oven, followed by analyses of anatomical characteristics and chemical composition. Composites containing 25% fiber reinforcement were produced using an orthophthalic unsaturated polyester matrix catalyzed with methyl ethyl ketone peroxide, with untreated fibers used as references. Thermal treatment induced significant modifications in fiber morphology and composition, including increases in cell wall fraction at 170 and 200 °C and higher cellulose contents at 140 and 170 °C. Mechanical performance was assessed through tensile, flexural (modulus of rupture—MOR), modulus of elasticity (E_B), and impact tests. Composites reinforced with heat-treated fibers exhibited lower apparent density and, notably, those treated at 230 °C showed markedly reduced water absorption and enhanced tensile strength compared with the control. Overall, treatment at 230 °C proved most effective, highlighting the potential of thermally modified eucalyptus fibers as viable reinforcements for high-performance, bio-based polymer composites. Full article

Efficiently separating propene and propane is paramount for the chemical industry but notoriously difficult due to their minimal size and volatility differences. Here, an efficient strategy to overcome this separation challenge was demonstrated through the design of bimetallic zeolitic imidazolate framework (ZIF)-based mixed-matrix membranes (MMMs). Thin-film composite (TFC) membranes were fabricated by integrating monometallic ZIF-8, ZIF-67, and a synergistic bimetallic ZIF-8-67 into a uniquely formulated ionic liquid–cellulose acetate (IL–CA) polymer matrix. Structural and morphological analyses confirmed the high crystallinity of the ZIF fillers and their seamless integration within the polymer. The resultant ZIF-8-67/IL-CA membrane exhibited notable separation performance, surpassing its monometallic counterparts by a threefold increase in both C₃H₆ permeance and C₃H₆/C₃H₈ ideal selectivity relative to the base membrane. Under industrially relevant mixed-gas testing, the membrane achieved a competitive separation factor of eight for propene over propane. These findings reveal that the strategic integration of bimetallic nodes in ZIFs can unlock synergistic properties unattainable with single-metal frameworks. This work presents a robust and scalable platform for developing next-generation membranes that defy conventional performance trade-offs, paving the way for efficient membrane-based olefin/paraffin separations. Full article

The growing emphasis on sustainable material design has intensified interest in bio-based additives as environmentally friendly alternatives to conventional synthetic modifiers. This study evaluates the effects of four natural compounds—cetyl alcohol, thymol, lanolin, and lecithin—on the thermal, rheological, mechanical, surface, and aging properties of regranulated low-density polyethylene (RLDPE). Post-consumer polyethylene waste was used as the polymer matrix, while biochar served as a sustainable reinforcing filler replacing carbon black. Differential scanning calorimetry, melt flow index measurements, rheological behavior, surface energy analysis, mechanical testing and thermo-oxidative aging assessments were conducted to assess structure–property relationships. Biochar increased stiffness, hardness, and impact resistance but reduced ductility and melt flow due to restricted chain mobility. The addition of natural compounds partially compensated for these effects by improving melt flow, modifying crystallization behavior, and enhancing resistance to thermo-oxidative degradation without severely diminishing mechanical performance. Cetyl alcohol promoted the highest crystallinity and flexural properties, lanolin exhibited the strongest plasticizing effect and improved post-aging ductility, while lecithin and thymol produced intermediate changes, with lecithin significantly increasing surface energy. These results indicate that selected natural additives can act as effective ecological plasticizers or processing aids in biochar-filled recycled polyethylene composites. Full article

One of the most critical damage modes affecting the structural performance of traditional composite materials, and therefore their durability, is the occurrence of interlaminar cracks (delamination), which are prone to grow under different loading conditions. In this study, the feasibility of repairing carbon fiber reinforced polymer (CFRP) laminates using structural adhesives was experimentally investigated by evaluating the Mode I interlaminar fracture toughness. Two unidirectional AS4 CFRP systems were analyzed, manufactured with epoxy 8552 and epoxy 3501-6 matrix resins. Mode I delamination behavior was characterized using Double Cantilever Beam (DCB) specimens. Three commercial structural adhesives were used in the repair process: two epoxy-based systems, (Loctite^® EA 9460™, manufactured by Henkel adhesives (Düsseldorf, Germany), and Araldite^® 2015 manufactured by Huntsman Advanced Materials (The Woodlands, TX, USA) and one low-odor acrylic adhesive, 3M Scotch-Weld^® DP8810NS manufactured by 3M Company (St. Paul, MN, USA). Adhesive joints were applied to previously fractured specimens, and the results were compared with those obtained from baseline composite specimens. The results indicate that repaired joints based on the 8552 matrix exhibited higher strain energy release rate (G_Ic) values, approaching those of the original material. The 3501-6 system showed increased fiber bridging, contributing to higher apparent fracture toughness. Among the adhesives evaluated, the acrylic-based adhesive provided the highest delamination resistance for both composite systems. Full article