Thermomechanical analysis of linear aromatic polyesters

The thermomechanical properties of linear aromatic polyesters, studied using thermomechanical analysis techniques, have been related to the chemical structure and methylene chain length. An increase in the number of methylene groups, the use of an asymmetric diacid, or random copolymerization of the repeating units of these polyesters, resulted in a lower linear thermal expansion coefficient α, a lower Vicat softening temperature Ts, a lower heat deflection temperature Td, and a lower glass transition temperature Tg. With longer methylene sequence lengths, the influence of the methylene groups on the thermomechanical properties is predominant, the data are closer together. The values are generally highest for the terephthalate series and lowest for the copolymer series. Glass transition temperatures calculated from group contributions and measured experimentally agreed. The deflection temperatures approximated the glass transition temperatures and the Vicat softening points the melting temperatures.