Toughened polypropylene with balanced rigidity. V. Melt rheological properties

In continuation of our endeavor to develop and characterize the high performance polypropylene composites and their toughening master batches (TMBs), we report here the melt rheological properties of toughened polypropylene with balanced rigidity (TRPP). The relations of shear stress (τ), shear rate $(\dot{\gamma})$ , apparent viscosity (η a ), temperature (T) and compositions of TRPPs were systematically investigated. Experimental data revealed that under ordinary shear flow conditions, the TRPP melts showed a pseudo‐plastic feature. Based on the complexity of the melt flow of the blended poly‐component/multiphase polymer system and together with our experimental and related literature results, the relationship between η a and T for blended polymer melts was recommended to be expressed by the equation: log η a  = α 0  + α 1 /T, where α 1 was defined as the temperature coefficient of apparent viscosity. The relationship between τ and $\dot{\gamma}$ can be expressed by the equation: $\tau = \hbox{k} \dot{\gamma}^{\rm n}$ , and the exponent n is decreased as τ increasing. At a given τ or $\dot{\gamma}$ , the η a of TRPPs decreased with ethylene‐propylene to styrene‐butadiene elastomer ratios from 20/80 to 100/0, increased with total elastomer content in TRPP and decreased with elastomer amount in TMB increasing. The manner of changes in η a with compositions were not affected by the τ or T. Copyright © 2001 John Wiley & Sons, Ltd.