The present work is an attempt to study the effect of different surface treatments of flax fiber on the mechanical properties of the natural fiber reinforced natural rubber (NR) composites. In this study, flax fiber was chopped to 1, 1.25, and 1.5 cm in length and mixed with NR in two roll mill. The composite of 20%, 30%, 40%, and 50% fiber loading was prepared from each fiber length. Tensile analysis showed that a 1.25 cm fiber length composite of volume 40% has higher tensile strength compared to others.Hence, this optimized the fiber length and loading has opted for further study. Flax fiber was treated with NaOH and laccase and reinforced into an NR matrix. Properties like tensile strength, hardness, relative density, water diffusion, scanning electron microscope (SEM) and Fouriertransform infrared spectroscopy (FTIR) for surface treated and untreated natural fiber-reinforced NR composites have been investigated and compared. The reduction in the hydrophilic characteristics of the NaOH and laccase treated fiber was evident from FTIR analysis and increase in the crystallinity index of the fiber depicted by X-ray diffraction (XRD) results. SEM analysis showed the enhanced interfacial interaction of treated flax fiber NR composite compared to untreated composite due to the removal of non-cellulosic contents in fiber and an increase in the surface roughness after treatments. Further, an increase of 9% and 27.4% in tensile and tear strength was found in NaOH treated flax fiber reinforced NR composite.

In the reported study, two composites, namely sisal-wool hybrid composite (SWHC) and pineapple leaf fibre(PALF)-wool hybrid composite (PWHC) were prepared by mixing natural rubber with equal quantities of wool with sisal/PALF in a two-roll mixing mill. The mixture was subjected to curing at 150 °C inside a 2 mm thick mold, according to the curing time provided by the MDR. The physico-mechanical properties of the compositeviz., the tensile strength, elongation, modulus, areal density, relative density, and hardness were determined and compared in addition to the solvent diffusion and thermal degradation properties. The hybrid composite samples were subjected to accelerated aging, owing to temperature, UV radiation, and soil burial tests. The cross-sectional images of the composites were compared with a scanning electron microscopic analysis at different magnifications. A Fourier transform infrared spectroscopic analysis was conducted on the hybrid composite to determine the possible chemical interaction of the fibres with the natural rubber matrix.