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

The melt-how behaviour of untreated and treated short-sisal-fibre-reinforce d styrene-butadiene rubber (SBR) composites were analysed by using an Instr on capillary rheometer. The effects of fibre breakage, length, concentratio n and shear-rate/stress on melt viscosity have been studied. The fibre brea kage was analysed before and after extrusion and the polydispersity index(P DI) was estimated. It was found that these composites behave as pseudo-plas tic 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 f ibre and the rubber matrix. The dependence of melt viscosity on temperature , flow behaviour index, n', melt elasticity, extrudate distortion and defor mation of these composites were analysed. Finally, die-swell measurements w ere carried out to understand the elastic effects. The extruded samples wer e analysed by optical and electron microscopy in order to study the surface morphology and extrudate deformation of these composites. (C) 2000 Elsevie r Science Ltd. All rights reserved.