DIFFUSION OF PHENOL IN STRETCHED POLYESTER FILMS

The effect of stretching of polyester films on the diffusibity of phenol has been studied. The films were prepared by the uniaxial stretching under a constant width or simultaneously biaxial stretching in several magnifications. The diffusion coefficient was determined from the permeability measured using an apparatus described in the previous paper as a function of phenol concentration. Then, the following results were obtained; (1) The diffusion coefficient of phenol in the amorphous region of polyester film was markedly dependent on the concentration of phenol. (2) The diffusion coefficient of phenol at a constant concentration and temperature, increased at the initial stage of stretching, then decreased with increasing the stretching ratio.(3) The apparent activation energy, calculated from the temperature dependence of diffusion coefficient, decreased with increasing the concentration of phenol. From these results, the internal fine structure of stretched polyester films were discussed relating to the change of the configurational entropy depending on the sorbed phenol. It was suggested that the amorphous polymer chains were ordered more tightly as increasing the stretching ratio, and this structural change leveled off at a certain magnification; about 3.5 times for uniaxial stretching and about 2.5 times for simultaneously biaxial stretching.