Equilibrium Swelling of Poly( p -phenylene sulfide) in Toluene-Ethanol Mixtures

Equilibrium swelling of poly(p-phenylene sulfide) (PPS) plates was examined in mixtures of toluene and ethanol at 60 °C as a function of the volume fraction u 2 of ethanol in the mixed liquid. The plot of relative increase in weight of swollen PPS plates against u 2 is found to deviate upward from the straight line connecting the two data points at u 2 = 0 (pure toluene) and u 2 = 1 (pure ethanol), indicating that swelling of PPS plates may be increased by coexistence of ethanol with toluene. Such experimental data are analyzed on the basis of the Flory-Huggins theory, assuming that both toluene and ethanol can interpenetrate only into amorphous regions in PPS plates but not into crystalline regions and also that both the thermodynamic interaction parameters between PPS and toluene and between PPS and ethanol are independent of the volume fraction of PPS molecules in swollen amorphous regions in PPS plates. The experimental values may be quantitatively reproduced by the theoretical ones calculated with the value of the average thickness of amorphous regions in the lamellar stacking structure in a PPS plate determined by small-angle X-ray scattering.