Melt flow behavior of short coir fiber reinforced natural rubber composites

The melt Bow behavior of natural rubber composites containing untreated, acetylated and gamma ray irradiated coir fibers was studied using an Instron Capillary Rheometer. Coir fibers of length 10 mm were used at different loading, viz., 5, 10, 20 and 30 phr. The dependence of melt viscosity, how behavior index (n') and extrudate deformation of the composites with shear rate, shear stress and loading of fibers was analyzed. The pseudoplasticity of the melt increased with fiber loading. At low level of fiber loading, the compound exhibited increased viscosity but at high fiber loading the compound showed low viscosity. This may be attributed to the formation of a sheath-core structure at high loading where fiber is concentrated at the core of the extrudate. Incorporation of fibers decreased the extrudate deformation and die swell and this improvement was more prominent at higher fiber loading.