Dilatometric Studies of High Polymers. I. Second-Order Transition Temperature

By means of a density balance, the relationship between intrinsic viscosity and dilatometric properties is established for polyethylene terephthalate. The most pronounced property change associated with increasing intrinsic viscosity was observed to be the second-order transition temperature. The relationship between crystallinity and dilatometric properties is presented for 3 aromatic polyesters. In every case, increased crystallinity in the polymers is associated with higher second-order transition temperatures, larger transition range, higher density, and lower volume coefficients of expansion. Second-order transition temperatures, densities at 0°C, and volume of coefficients of expansion are presented for a number of polyesters and vinyl polymers to illustrate the effects of chemical structure as well as physical state on these dilatometric properties. Illustration of the effect of copolymerization on second-order transition temperatures is made with a copolyester system.