Dependence of flow behaviour on carbon black distribution in polyblend systems

The flow behaviour of four blend systems was determined at four shear rates and three processing temperatures using an extrusion rheometer. The blends were based on natural rubber/polybutadiene elastomers and were prepared using various mixing sequences with the carbon black being added in different ways.The degree of die swelling was found to depend on the blending technique, the processing temperature and the extrusion rate. A theoretical model was used to calculate the stored elastic energy, shear modulus and relaxation time. Melt fracture was observed when the carbon black was premixed in just one component of the blend.