Pressure effect on viscosity for atactic and syndiotactic polystyrene

The effect of pressure on viscosity is an important but often overlooked aspect of the flow properties of polymeric materials. Generally, an exponential dependence (the so-called Barus equation: ?=?0exp(?P)) can be adopted to describe this effect. In this work two polymers (an atactic and a syndiotactic Polystyrene) were characterized as far as the effect of pressure on viscosity is concerned by analyzing the non-linearities in the so-called Bagley plots. The results obtained show that for both materials the average value of ? is in the range 1-3×10-8Pa -1. No relevant effects of temperature and shear rate were detected in the range analyzed. The data obtained were also described by means of a Cross-Vogel model, which reproduces the main features of experimental data.