Dynamic mechanical relaxations of polyterephthalates based on trimethylene glycols

The dynamic mechanical relaxations of poly(trimethylene glycol terephthalate) (PTMT), poly(ditrimethylene glycol terephthalate) (PDTMT) and two copolymers obtained from them have been studied between ? 150 and 200°C with a dynamic viscoelastometer. The four polymers show three relaxations that are designated α, β, and γ in order of decreasing temperature. The α relaxation is considered to be the glass transition of the polymers. The β relaxation is wider and weaker than the α, as normally occurs in the polyester series. The γ relaxation takes place at temperatures below ? 100°C and is usually overlapped by the β relaxation. The influence of thermal and mechanical histories on the nature, location, and intensity of the three relaxations is studied and discussed.