MELT FLOW BEHAVIOR OF SHORT COIR FIBER-REINFORCED NATURAL-RUBBER COMPOSITES

The melt Bow behavior of natural rubber composites containing untreate d, acetylated and gamma ray irradiated coir fibers was studied using a n Instron Capillary Rheometer. Coir fibers of length 10 mm were used a t different loading, viz., 5, 10, 20 and 30 phr. The dependence of mel t viscosity, how behavior index (n') and extrudate deformation of the composites with shear rate, shear stress and loading of fibers was ana lyzed. The pseudoplasticity of the melt increased with fiber loading. At low level of fiber loading, the compound exhibited increased viscos ity 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. Inco rporation of fibers decreased the extrudate deformation and die swell and this improvement was more prominent at higher fiber loading.