Polyvinyl alcohol film was cast from a 10% aqueous solution, which was swollen in a 50% ethanol solution and stretched 3 folds, followed by drying and heat-setting at 210°C for 2min. (I-film). It was contracted by 30% by heating at 226°C for 5 sec. in a free state and then dyed with_??_ Congo Red at 70°C (II-film).
II was stretched to the original length at room temperature in a moistened state and again contracted, the amount of contraction being controlled by changing the amount of regain and the temperature (not over 120°C). The dichroic orientation degree f_D, X-ray orientation degree f_x and the crystallinity X of the film were determined at each stage of the stretching and contraction. From these parameters the stretching degree of the amorphous chain v_a relative to the isotropic state, was calculated and plotted against the observed f_D.
As the results, it was found that f_D changes with v_a nearly reversively by the stretching and the contraction, and the amorphous part deformes according to the Kratky's first deformation mechanism under the experimented conditions.