The rheological properties of a three block butadiene-styrene copolymer

The rheological properties of a block copolymer consisting of the three blocks polystyrene-polybutadiene-polystyrene (PS-PBD-PS), and of industrial PBD rubber have been studied in the 0·02–0·10 kgf/cm2 shear stress range at 60–110°C during long lasting deformation (up to 5 × 104 sec). Viscous flow commences at the deformation start, and is non-Newtonian for both the polymers. The logarithmic viscosity as a function of inverse temperature is non-linear which means that the Frenkel-Andrade equation cannot be used to calculate the temperature coefficient of viscosity. The equation most suitable for describing the temperature dependence of the viscosity of our 3 block copolymer is the Allen-Fox equation. The block copolymer, in contrast with the PBD elastomer, showed a temperature dependence of the viscosity coefficient, but the temperature coefficient of viscosity was independent of shear stress in the case of both the polymers.