Solvent Crystallization and Heat Resistance of Amorphous PET Film with Ethyl Acetate

PET films were dipped in solvents and subsequently tested for heat-resistance at low temperatures and low elongation. The results indicate that acetaldehyde can impart high heat-resistance to the film and prevent solvent leakage. The solvent was selected to investigate the strength of the negative charge of the aldehyde carbonyl group and find a solvent which would further enhance the heat-resistance of the film. Solvents with carbonyl groups containing strong negative charges were chosen while considering the dielectric constant, which, in general, strongly influences solvent crystallization. Dimethyl sulfoxide was selected as a solvent because of its extremely high dielectric constant. For comparison, ethyl acetate, which has a lower dielectric constant, was chosen as a solvent along with acetaldehyde, which has a moderate dielectric constant. The PET films were inserted in boiling water after elongation, at which ethyl acetate caused a high heat-resistance of 1471 cm-1. This result showed that a low dielectric constant is not correlated with the heat-resistance of the resulting film.