Functional Composite Materials最新文献

In recent decades, composite materials have gained worldwide attention in research due to their unique properties such as low weight, low density, high mechanical strength, biodegradability, and eco-friendliness. This study investigates the effect of coir fiber and coir pith loadings on the properties of polyethylene composites. The polyethylene composites were prepared with coir fiber at volume fractions of 20%, 50%, and 80%, while a hybrid composite was fabricated with 25% coir fiber and 25% coir pith. The results showed that the hybrid composite exhibited improved properties due to the combined action of coir fiber and pith. In contrast, the polyethylene composite reinforced with only coir fiber degraded more rapidly above 375 °C, indicating lower thermal stability compared to the hybrid composite. The study also explored the feasibility of processing hybrid polymer composite laminates using compression moulding. The findings revealed that the reinforcement volume fraction significantly influenced the mechanical properties. The hybrid composite demonstrated superior mechanical performance compared to the fiber-only composites, owing to the synergistic effect of fiber and pith. Additionally, the hybrid composite exhibited excellent electrical insulation behavior and was successfully fabricated into various types of strain insulators for electrical applications.

The global polymer waste crisis is intensified by the fundamental contrast between recyclable thermoplastics and intractable thermosets. This article comments on how vitrimers—polymers containing Covalent Adaptable Networks (CANs)—are bridging this recycling gap. The current research focuses on engineering vitrimers from both traditionally unrecyclable thermoset matrices and high-volume commodity thermoplastics. We detail the unique chemistry that allows these materials to be reprocessed, reshaped, and self-healed while maintaining structural integrity. Specific innovations include the scalable chemical protocols that chemically upcycle complex waste streams into high-purity molecular feedstocks. Vitrimers establish a scalable, chemical foundation for achieving true closed-loop circularity across the entire polymer value chain.

In this study, rice husks from two different varieties were incorporated into PLA as reinforcing fibres using twin screw extrusion. The developed rice husk reinforced PLA composites were characterized for their thermal, mechanical, chemical, biodegradable and rheological characteristics. Thermal conductivities for the developed PLA rice husk composites were generally lower than 0.26 W/mK, but higher than that for neat PLA. Surface morphologies for the developed composites indicated presence of micropores and delamination indicating inadequate adhesion between the PLA matrix and the rice husk fibres. Broadening of the -OH peaks with an increase in rice husk fibres was observed in the FTIR spectra. The maximum stress for all the developed PLA rice husk composites was less than 67 MPa, the maximum stress for neat PLA, with PLA composites developed with 5% rice husks having the highest maximum stress for all composites developed. Modulus of elasticity increased with an increase in rice husk reinforcing fibres for both varieties. Biodegradation results indicated that the hydrophilic rice husks resulted in moisture ingression into the composites but would enhance hydrolytic degradation over a longer testing duration. The rheological results showed that an increase in rice husk fibre content reduced the flowability of the developed PLA rice husk composites, which affects their potential application.

The asphalt industry continues to adapt to challenges arising from the limited availability of bituminous binders with consistent properties. One such challenge is the use of Re-refined Engine Oil Bottoms (REOB). Detectable only through advanced chemical analysis, REOB can modify bitumen properties in ways that are often overlooked and, in many cases, unexpected. This literature review examines the classification of REOB, the variability of its production, the regulatory challenges surrounding its use and the properties of REOB modified bitumen. Particular attention is given to technical concerns, including ageing susceptibility, phase behaviour changes, increased mixture stiffness, and interactions with other additives. The review also critically evaluates publications presenting favourable claims for REOB use, highlighting areas where conclusions may be premature. Recommendations are provided for researchers, regulatory bodies, and industry stakeholders to promote safe and informed implementation. Special focus is placed on regions outside the United States, where REOB use is poorly documented and recent cases of unexpected workability problems and premature pavement distress have drawn attention to its potential risks.

The increasing demand for sustainable antimicrobial materials and the environmental burden of crustacean shell waste necessitate exploration of alternative chitosan sources with comparable bioactivity and superior cost-effectiveness. This proof-of-concept study investigates chitosan extraction from shells of Archachatina marginata, presenting a green chemistry approach to waste valorization. Sequential alkali deproteinization, acid demineralization, and alkaline deacetylation yielded 12.3% chitosan from dry shell weight. X-ray diffraction analysis revealed optimal crystallinity (65–70%) with well-ordered crystalline domains, while FTIR spectroscopy confirmed successful deacetylation (75.39%) with diagnostic bands indicating free amino group availability for antimicrobial action. Antimicrobial evaluation using disk diffusion and broth microdilution assays against five bacterial pathogens demonstrated significant activity against Staphylococcus saprophyticus (39.00 ± 1.00 mm zone of inhibition), S. aureus (34.67 ± 0.58 mm), Klebsiella pneumoniae (26.67 ± 0.58 mm), and Escherichia coli (23.67 ± 0.58 mm), with minimum inhibitory concentrations ranging from 0.0781 to 0.3125 mg/mL for susceptible strains. Notably, Salmonella typhi exhibited complete resistance (MIC > 40.0 mg/mL), representing a unique selectivity pattern not previously documented for alternative chitosan sources and highlighting organism-specific resistance mechanisms. The natural chitosan-CaCO₃ biocomposite structure offers potential synergistic properties for applications beyond antimicrobial uses. Literature-based economic extrapolations suggest potential 54–58% production cost reduction compared to crustacean sources, driven by zero-cost feedstock acquisition and year-round availability. Environmental metrics derived from comparative analysis indicate potential 35–47% energy savings and 42–61% carbon footprint reduction. These findings position A. marginata shell-derived chitosan as a promising sustainable alternative warranting further investigation for food preservation, biomedical devices, water treatment, and biodegradable packaging applications, contributing to circular economy waste valorization strategies while addressing global sustainability challenges.

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In this work, the influence of different screw designs and speeds of a twin-screw extruder on the mechanical properties of nylon 6/graphene nanoplatelet (GnP) nanocomposites is investigated. Nanocomposites are prepared using 3 wt% GnPs and three screw designs designated as high, medium and low shear screws at speeds of 100, 200 and 300 rpm. Tensile and Charpy impact tests are performed to investigate the mechanical properties of nanocomposites. An increase in the Young’s modulus (in the range of 4.3% to 29.7%) is observed for all nanocomposite samples as compared to neat nylon 6 while tensile strength is either reduced or increased. It is also observed that nanocomposites have a lower strain at break (in the range of 82.9% to 95.2%) and a corresponding reduction in the tensile energy at break (in the range of 88.3% to 97.3%). Furthermore, nanocomposites exhibit lower impact strength (in the range of 25.2% to 65.6%) compared to neat nylon 6, and the screw designs influence this impact strength variation.

This study presents a spectrophotometric method for estimating the film thickness of polymer coatings. Four polymers Polyvinyl alcohol (PVA), Polyethylene glycol (PEG), Polyacrylamide (PAM), and Polyvinyl acetate (PVAC) were prepared in ten different concentrations (20–110 g/dm³) and deposited onto glass slides by drop casting. Absorbance and transmittance were measured over a wavelength range of 340–540 nm using a UV–VIS spectrophotometer, and optical constants were calculated to estimate film thickness. Results showed that film thickness decreased with increasing concentration for PVA (2.90 to 0.25 nm) and PVAC (4.97 to 4.12 nm), while PEG (2.07 to 6.25 nm) and PAM (1.18 to 8.86 nm) exhibited increasing trends. Surface free energy decreased with increasing film thickness across all polymers, with maximum values of ~ 57.51 mJ/m² and minimum values of ~ 41.05 mJ/m². Contact angle measurements revealed that PVA and PAM became more hydrophobic with thicker films, whereas PEG and PVAC showed increased hydrophilicity. These findings demonstrate that spectrophotometry can provide a low-cost, non-destructive approach to estimating polymer film thickness and related surface properties. The method is suitable for rapid characterization in materials science, coatings engineering, and surface modification studies.

Polylactic acid (PLA) is highly regarded among polymeric materials due to its versatile properties, making it suitable for a variety of applications. This study aimed to functionalize pure PLA by blending it with gum Arabic (GA) through electrospinning, a technique recognized for producing nanofibrous materials with enhanced characteristics. The research further assessed the mechanical and microstructural properties of PLA/GA composites using a range of analytical methods, including tensile testing, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). A thorough analysis of the results indicated that the electrospinning technique successfully produced bead-free nanofibers. The introduction of 5 wt% GA and higher concentrations resulted in a slight increase in the formation of sharp Bragg peaks while significantly reducing the XRD intensity of the PLA/GA composites by approximately 93%, reflecting an overall decrease in the crystallinity of the composite. This reduction notably affected the ultimate tensile strength (UTS), which dropped by around 49% below the 5 wt% GA addition, while ductility experienced an increase of about 78%. Moreover, the incorporation of GA transformed the smooth surface morphology of pure PLA into a rougher texture in the PLA/GA composite across all considered GA concentrations, further indicating a decrease in crystallinity and an increase in the amorphous character of the material.

Composite materials are especially well-suited for harsh environmental conditions and offer damage resistance due to their high corrosion resistance and good strength-to-weight ratio. Temperature, moisture content, radiation exposure, UV and infrared radiation, and thermal cycling are the main variables that affect their performance. To assess the mechanical properties and structural stability of the carbon/epoxy composite, these studies concentrate on its three-point bending behavior and wear test. We can determine the stiffness, strength, and resistance to load deflection of this type of composite material by assessing its flexural strength. Through the wear test, we will evaluate the materials’ resilience to wear caused by frictional forces and their durability. In addition to improving their development stage category and guaranteeing resistance to degradation in harsh conditions, knowing this would help us understand how environmental factors impact the mechanical performance of these composites. These results demonstrate that it is much better to optimize the use of composite in high-demand applications, especially in the aerospace application sector.