Functional Composite Materials最新文献

Maintaining the structural stability and electrical conductivity of self-assembled nanofiller assemblies in stretchable polymer matrix under repeated mechanical deformation remains a central challenge in the development of reliable flexible electronic devices. Cyclic bending often induces dynamic reorganization of conductive nanofillers within elastomeric matrices, leading to progressive disruption of percolated pathways and a concomitant increase in electrical resistance. Here, we present a comprehensive real-time analysis of stress-induced self-organization and network formation of conducting nanofillers using in-situ mechanical deformation and thermal annealing. Simultaneous electrical conductivity measurements were performed during film stretching inside a synchrotron-based ultra-small-angle X-ray scattering instrument. This multimodal approach enables direct visualization of hierarchical nanofiller assembly and restructuring across multiple length scales under periodic stress. By systematically exploring a diverse set of polymer matrices and conductive fillers with distinct geometries and surface functionalities, we elucidate the intra- and intermolecular reinforcement mechanisms that mitigate shear-induced damage, stabilize interpenetrating networks, and delay conductive network fragmentation. Our findings highlight the critical role of non-bonded polymer-filler and filler-filler interactions near the percolation threshold in governing electromechanical durability. These insights provide a rational framework for designing mechanically robust, strain-tolerant conductive nanofiller inks and nanocomposites for next-generation flexible and wearable electronic applications.

In this work, we report a high-performance polyurethane (PU) nanocomposite cathodic electrodeposition (CED) coating, which has been reinforced with nitrogen-doped carbon dots (NCDs) obtained from the hydrothermal treatment of shrimp shells derived chitosan. The synthesized NCDs show a quasi-spherical shape with an average diameter of around 4–6 nm, confirmed by FT-IR, XRD, and TEM analysis. The incorporation of the NCDs into the PU polymer results in strong interfacial interactions between the polymer chains and the NCDs, resulting in a better and more adherent film formation. The NCDs provide nano-roughness to the coating surface, resulting in an increased water contact angle via enhanced nano-roughness. The incorporation of the NCDs also results in the filling up of the microvoids created in the film during solvent evaporation and results in the formation of longer diffusion paths for the corrosive species. EIS analysis exhibits that the incorporation of the NCDs into the nanocomposite coating enhances the charge transfer resistance, showing better anti-corrosion properties of the coated samples. However, higher dosage of NCD solution cause agglomeration and reduction in film property. Overall, bio-derived NCDs provide a minimalistic, scalable, and environmentally benign route to electrodeposited PU coatings with superior anticorrosion performance.

Graphical Abstract

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.

Graphical Abstract

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.