Effects of high speed electrons on the structure of polyethylene terephthalate

Polyethylene terephthalate (PET) films were irradiated with high speed electrons in vacuo. Their infrared spectra, solubility, and degree of swelling in o‐chlorophenol were measured as a function of the irradiation dose. The investigation has shown that irradiation causes both crosslinking and degradation. In the absence of air, crosslinking predominates over chain scission. The irradiation dose required for crosslinking of PET by far exceeds that required for crosslinking of polystyrene. Irradiation of PET is accompanied by the formation of polyphenyl systems. The initial partly crystalline PET becomes completely amorphous on irradiation. Irradiation causes isomerization of O(CH2)2O groups in the polymer chain from the trans to the gauche form. Isomerization of O(CH2)2O groups under irradiation may be interpreted as indicating that a part of the ionizing radiation energy is dissipated and transformed into thermal energy.