Abstract
Swelling in chloroform at 30°C was studied for biaxially oriented poly (ethylene terephthalate) (PET) films which are commercially available for the many purposes. Results obtained are as follows:
(1) The anisotropy of the swelling was confirmed for the films from the dynamic loss tangent (tan δ) absorption da, behavior measured in the machine and transverse directions which are perpendicular to the direction to which solvent diffuses.
(2) The swelling mechanism was directly associated with the thickness increase at the initial stage of swelling, but not with that at the equilibrium swelling.
(3) The Case II swelling mechanism was observed for the films which exhibit the smaller amount of the equilibrium swelling in the amorphous region. This fact was in good agreement with the information of the fine structure of PET films related to the Case II swelling.
