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The main objective of this study is to investigate the effect of curing temperature on the mechanical properties of hemp fiber reinforced polymer (HFRP) composites. In this study, hemp fiber was considered as a reinforcement and epoxy resin with hardener as a matrix. The mercerization process was used to remove contaminants from the fiber surface. The overall volumetric fraction used was 40% fiber and 60% matrix. One composite sample was cured at open temperature (27 ± 3 °C) for 15 days and others at elevated temperatures such as 80, 120 and 160 °C for various durations such as 1, 2, and 3 h (h). Different mechanical tests were performed under ASTM standards to examine the mechanical performance of HFRP composites. The tensile and compressive properties such as Young's modulus, tensile and compressive strengths are higher in the specimens cured at 120 °C for 3-h. The flexural strength and stiffness are maximum in the composites cured at 80 °C for 3-h. The maximum interlaminar shear strength representing the composite's resistance to delamination is observed at 120 °C for 3-h curing condition. The Fourier transform infrared (FTIR) study identifies that the chemical treatment has reduced the impurities present on the fiber surface. Scanning electron microscopic (SEM) studies indicate better fiber/matrix adhesion in specimens cured at elevated temperatures than those cured at open temperature. Finally, this study emphasizes that curing at elevated temperature (120 °C for 3-h) improves the mechanical performance of the NFRP composites. [ABSTRACT FROM AUTHOR]

Current research intended the fabrication of highly durable conducting rubber products of low cost and wide applicability in the field of electronics. Chlorinated natural rubber (Cl-NR) reinforced with copper alumina (Cu-Al2O3) nanocomposites were fabricated by a solvent-free and economically viable industrial compounding technique with special attention to structural, morphological, rheometric curing behaviour, flame retardancy, electrical conductivity, dielectric, thermal and mechanical properties. FT-IR spectra confirmed the presence of Cu-Al2O3 in Cl-NR. The XRD investigation showed the crystalline peaks of Cu-Al2O3 in Cl-NR nanocomposites. The SEM and TEM results indicated that the nanoparticles were uniformly dispersed into the chlorinated rubber in the nano regime. The DSC results indicated that the addition of nanoparticles into the rubber matrix increased the glass transition temperature of the composites. The conductive metal oxide particles in the rubber accelerate the vulcanization process, which could be more beneficial in the industrial sector. The AC conductivity, dielectric properties, tensile strength, modulus, tear strength, heat build-up and hardness of nanocomposites were greatly increased, whereas the elongation at break, abrasion loss and resilience were decreased with the addition of nanoparticles to the chlorinated natural rubber. These increased mechanical properties of rubber nanocomposites with improved processability, controlled morphology and electrical properties are important parameters in the designing of flexible flame retardant electronic devices, electromagnetic induction shielding and conducting adhesive materials. [ABSTRACT FROM AUTHOR]

Present innovation demonstrates the fabrication, characterisation, thermal, flame retardancy, electrical conductivity, vulcanization and mechanical properties of zinc ferrite (ZnFe2O4) nanofiller inserted chlorinated natural rubber (Cl–NR) prepared by an industrial compounding technique. The interaction between ZnFe2O4 and Cl–NR was characterised by FT–IR. The uniform dispersion of nanofiller in the rubber matrix was confirmed by SEM and TEM analysis. XRD showed the structural changes of composite with the presence of crystalline peaks of ZnFe2O4 in chlorinated rubber. The flame retardancy and glass transition temperature of the rubber composites were significantly enhanced with the filler loading in chlorinated rubber was evident from LOI and DSC analysis, respectively. The vulcanization time of rubber nanocomposite was greatly reduced by the use of zinc ferrite that is an important factor for reducing the cost of the preparation of rubber goods. The tensile strength, tear resistance, modulus, hardness and heat build-up of nanocomposites were significantly increased with the addition of zinc ferrite whereas the abrasion loss, resilience and elongation at break were decreased. The electrical conductivity and dielectric properties of rubber nanocomposite were also investigated in various frequencies. The percolating network formed by ZnFe2O4 in Cl–NR results in the high electrical conductivity and dielectric behaviour of the fabricated composites. The higher mechanical properties, glass transition temperature and the electrical conductivity of fabricated composites were beneficial in designing lightweight and highly durable flexible electronic devices based on chlorinated natural rubber. [ABSTRACT FROM AUTHOR]

Metal oxide nanofillers are a special type of additives in rubber composites that impart special qualities such as thermal resistance, tensile strength, electrical conductivity and heat capacity to rubbers. The heat conductivity of metal oxide through the rubber matrix reduces the vulcanization time of the rubber nanocomposites. Hence, the present work focused on the enhancement of these properties in natural rubber (NR) using zinc ferrite (ZnFe2O4) nanoparticles were prepared by a simple two-roll mill mixing technique. Structure, morphology, crystalline nature, cure characteristics, swelling, thermal and mechanical properties of the NR composites containing ZnFe2O4 were analysed in detail. FTIR and UV analysis proved the interaction of zinc ferrite with the macromolecular chain of NR. The XRD patterns of composite films revealed a decrease in amorphousness of NR with well-dispersed crystalline peaks of nanoparticles in the polymer. SEM images evidenced the morphological changes caused by dispersing zinc ferrite in the NR matrix. TEM analysis showed the uniform attachment of nanoparticles in the polymer. Glass transition temperature obtained from DSC was improved with the addition of zinc ferrite. The results from TGA showed that the presence of ZnFe2O4 in the polymer matrix greatly increases the thermal stability of NR. The metal oxide nanofiller significantly reduced the cure and scorch time of the NR composites. The mechanical properties of rubber nanocomposites showed that the addition of ZnFe2O4 improved their modulus, tensile strength, hardness, abrasion resistance and heat build-up, whereas the elongation at break and resilience decreases. The permeation and diffusion of nanocomposites were observed to be diminished with the size of penetrating solvents and also with the loading of filler. Overall, zinc ferrite nanoparticles could be used as a potential filler for improving the processability, mechanical strength, thermal stability and solvent resistance of natural rubber. [ABSTRACT FROM AUTHOR]

In the future, materials will need to be biobased and produced sustainably without compromising mechanical properties. To date, in many cases, the advantages of the bio-origin of the raw material are overridden by the environmental impact of the process. In the present study, we have developed a novel composite material based on woven hemp fabric which reinforce a thermoset polymer produced from birch bark, a low-value forestry byproduct. Results show that this fully biobased composite has specific stiffness and strength equivalent to those of flax fibre-reinforced petroleum-based epoxy composites and slightly lower than glass fibre-reinforced petroleum-based epoxy composites. The sustainability of the material was also evaluated by life-cycle assessment from cradle to gate and showed significantly superior performance with respect to the potential global warming impact than commercial benchmark materials. Furthermore, toxicology studies showed no endocrine disruptive activities. This is an important proof of concept study demonstrating that biobased structural materials can be produced sustainably. [Display omitted] [ABSTRACT FROM AUTHOR]

Three different organo-modified clays have been incorporated by sonication into a high performance epoxy resin before the cross-linking reaction. The X-ray analysis indicated that, depending on the organoclay type, partially exfoliated and partially intercalated composites have been obtained. As shown by the DSC analysis, the clay addition seems to interact with the cross-linking reaction. The incorporation of organoclay into epoxy increased free volume and micro-voids in the samples. Sorption of water in the composite samples resulted higher than that of the pristine resin, whereas the diffusion coefficient is significantly lower. The lower value of diffusion makes the permeability at ambient conditions lower than the pristine resin. The elastic modulus of the composite sample results higher than that of the pristine resin, especially in the temperature region around the glass transition. The presence of organoclay in epoxy matrix decreased the glass transition temperature, whether the nanocomposites were in a dry or wet condition. [ABSTRACT FROM AUTHOR]

Vulcanization and reinforcement are critical factors in governing the ultimate practical applications of elastomer composites. Here we achieved a simultaneous improvement of curing and mechanical properties of elastomer composites by the incorporation of a functionalized halloysite nanotubes–silica hybrid (HS-s-M). Typically, HS-s-M was synthesized by 2-mercapto benzothiazole (M) immobilized on the surface of halloysite nanotubes–silica hybrid (HS). It was found that the HS-s-M uniformly dispersed in the styrene-butadiene rubber (SBR) matrix, offering more opportunity for M molecules to communicate with rubber. In addition, the physical loss of accelerator M from migration and volatilization was efficiently suspended. Therefore, SBR/HS-s-M composites showed a lower curing activation energy and a higher crosslinking density than SBR/HS composites. Moreover, a stronger interfacial interaction between HS-s-M and SBR was formed by the cross-linking reaction, giving a positive contribution to the eventual mechanical properties. The possible vulcanization and reinforcement mechanisms of SBR/HS-s-M composites were also analyzed in detail. [ABSTRACT FROM AUTHOR]