The thermodynamics of filled polystyrene

Mercury and volumetric dilatometry under pressure have been used to study the specific volume of block polystyrene (BPS) samples containing 0, 1, 5, 10, 20, 30 or 50 wt.% of glass powder, as a function of temperature in the 25–200°C range at pressures from 1 to 2000 kg/cm2. Small amounts of glass powder (about 1%) were found to alter greatly the polymer structure; this became evident by increases in the density and internal pressure, as well as by a reduction in compressibility. Filler amounts greater than 1 wt.% creates loosely packed boundary layers of polymer in the system which have larger compressibility. The analysis of the results using vacancy theory is the basis of our assumption that the volume of the free energy of the polymer in its blends, and the temperature, T2, at which the residual entropy becomes zero, will change in parallel with the isothermal compressibility of the melt.