Morphology and melt rheological behaviour of short-sisal-fibre-reinforced SBR composites

The melt-flow behaviour of untreated and treated short-sisal-fibre-reinforced styrene–butadiene rubber (SBR) composites were analysed by using an Instron capillary rheometer. The effects of fibre breakage, length, concentration and shear-rate/stress on melt viscosity have been studied. The fibre breakage was analysed before and after extrusion and the polydispersity index(PDI) was estimated. It was found that these composites behave as pseudo-plastic materials. At low shear rates, the short fibres increase the viscosity much more than at high shear rates. There was an increase in viscosity upon chemical treatments owing to the strong interfacial adhesion between the fibre and the rubber matrix. The dependence of melt viscosity on temperature, flow behaviour index, n′, melt elasticity, extrudate distortion and deformation of these composites were analysed. Finally, die-swell measurements were carried out to understand the elastic effects. The extruded samples were analysed by optical and electron microscopy in order to study the surface morphology and extrudate deformation of these composites.