The aim of the present study is to investigate the dynamic mechanical and thermal properties of hybrid jute/sisal fibre reinforced epoxy composites. The hybrid composites were prepared by hand layup technique having total fibre loading of 30% by weight with different weight ratios of jute and sisal fibres. Dynamic mechanical properties such as storage modulus (E 0 ), loss modulus (E 00 ) and damping (Tan) were investigated in the temperature range of 30-200 C. The thermal stability of the prepared composites was studied using thermogravimetric analysis. Other thermal properties such as glass transition temperature (T g ), crystallization temperature (T c ) and decomposition temperature (T d ) were also obtained by differential scanning calorimetry. The results indicated a positive effect of hybridization in terms of increase in dynamic mechanical and thermal properties. Storage modulus, loss modulus and T g were found to be higher for hybrid composite having a higher percentage of jute fibres.

Due to the dominating advantages of natural fibres such as biodegradability, eco-friendliness, nominal cost, low density and high specific strength, they are being used opposite to synthetic fibres in many industrial applications. Despite many advantages, these fibres face some limitations such as higher moisture uptake, quality variations, low thermal stability, and poor compatibility with polymeric matrix. To overcome these limitations, chemical treatments of these fibres were found to be the most suitable method to improve adhesion with polymers, increase their strength and water absorption resistance, and improve their composite properties also. Among chemical treatments, alkali treatment is the most widely used and versatile surface modification method of the natural fibres. A good number of research works have been carried out on effect of alkali treatment on the properties of natural fibres and its composites, which motivated for this review. In this paper, the effect of alkali treatment on the properties of natural fibres has been reviewed. In addition, the physical and mechanical properties, thermal analysis and tribological behaviour of its biocomposites are also reviewed. It was concluded that alkali treatment of natural fibres could provide enhanced properties of various bio-composites up to a great extent.

In recent years, researchers and scientists are facing problems in terms of environmental imbalance and global warming owing to numerous use of composite materials prepared by synthetic fibers and petrochemical polymers. Hence, an increasing attention has been devoted to the research and development of polymer composites reinforced with the natural fibers. The natural fibers are the most suitable alternative of synthetic fibers due to their biodegradability, eco-friendliness and acceptable mechanical properties. The natural fibers are attracting the researchers and scientists to exploit their properties by amalgamating them with the polymer. The properties of natural fiber reinforced polymer composites mainly depend upon various factors such as properties of fibers and matrices, fiber loading percentage, size and orientation of fibers, stacking sequences, degree of interfacial bonding, fiber surface treatments, hybridization and incorporation of additives and coupling agents. Tensile and flexural tests are the most important investigations to predict the applications of the materials. A good number of research has been carried out on tensile and flexural properties of natural fiber reinforced polymer composites. In this paper, a review on tensile and flexural properties of natural fiber reinforced polymer composites in terms of effects of fiber weight fraction, geometry, surface treatments, orientations and hybridization is presented. Moreover, recent applications of natural fiber reinforced polymer composites are also presented in this study.

In the present work, a novel physical treatment (PLA coating) of sisal fibres and its influence on the water absorption, static and dynamic mechanical properties of its composites has been presented. The treated sisal fibres were used consisted of alkali treatment and PLA coating to fabricate its polyester-based composites by hand lay-up technique keeping constant fibres content as 20 wt.% . Water absorption analysis was carried out in terms of water uptake (%), and sorption, diffusion and permeability coefficient. In addition, static properties were examined in terms of tensile, flexural and impact test, and dynamic mechanical analysis was performed in terms of storage modulus (E'), loss modulus (E″), damping (tanδ) and glass transition temperature (Tg). It was reported that the PLA-coated sisal composites showed the best performance in water absorption, mechanical and dynamic mechanical properties than pure sisal and alkali-treated sisal composites. There were 33%, 49%, 48%, and 27% improvement in water resistance, tensile strength, flexural strength and impact strength, respectively, of PLA-coated sisal composites as compared to that of pure sisal composite.

At low doses (10 and 25 ppm in drinking water), the effects of arsenic on hematopoietic indices and whole-brain neurotransmitter concentrations were more prominent in guinea pigs than in rats with some variability in the dose response.