The effect of heat on molecular rearrangements in amorphous, non-oriented polyethylene terephthalate☆

Abstract An arc-like structural model of amorphous polyethylene terephthalate (PETP) is based on experimental results from NMR with a paramagnetic radical probe, by calorimetry, dilatometric and optical measurements, and by other methods; some of the features of the intermolecular packing of amorphous or partly crystalline polymers have been established. The structural conversion sequence and the type of molecular movements during the change from an arc-like structure to the glassy state, and then through the devitrification range to the partly-crystalline state, have been evaluated.