The glass temperature of filled polystyrene as a function of pressure

The glass temperature (determined from the pressure-temperature curves during isochorous cooling) of PS samples filled with glass powder has been studied as a function of pressure. The results agreed well with the theory that the structure of the vitrified state can be described by a single structural parameter, namely the free volume ƒs in the polymer at the glass temperature (Tg). The ƒs values are not constant regardless of the determination method used, and show a tendency to increase with the filler content.