Sharkskin mechanism of high-impact polystyrene (HIPS) and rheological behavior of HIPS/TiO2 composites

The rheological behaviors of high-impact polystyrene (HIPS) and HIPS/TiO2 composites were investigated by use of a rheometer in the present article. HIPS exhibited a constant critical stress of the sharkskin in various temperatures, and the analysis indicated that the mechanism of sharkskin of HIPS was wall-slip and its special temperature dependency was determined by weak wall-melt adsorption. The experimental results also showed that the introduction of TiO2 into HIPS only slightly influenced the apparent viscosity (eta(a)) of the composites. Moreover, TiO2 exhibited an unusual effect on the non-Newtonian index of the composites at high shear rate. Both phenomena indicated the increase of inner free volume induced by TiO2 in molecularly rigid HIPS. Moreover, it was noteworthy that a featured stress could be used to label the dispersion of TiO2 in the HIPS matrix, and the numeric affinity of this featured stress and the critical stress of sharkskin revealed that both processes were relevant to the same molecular relaxation. (c) 2005 Wiley Periodicals, Inc.