Mechanism of plastic strain of glassy polymers. Amorphous polyethylene terephthalate

Various experimental methods have been used to study the strain behaviour of amorphous PET. The process of plastic strain is accompanied by storage of latent energy the amount of which with strain at first rises and then passes to a certain limit. On heating the deformed samples two-stage restoration of residual strain occurs. The low temperature stage of restoration is accompanied by the release of latent energy and its onset always corresponds to the temperature of deformation. The storage and annealing of latent energy are unrelated to change in the conformational set of the PET sample. The mechanism of plastic strain of amorphous glassy polymers on which are based the notions of the processes of generation and development of metastable plastic defects is proposed.