CHANGE IN ORIENTATION DUE TO SWELLING OF UNIAXIALLY STRETCHED POLYVINYL ALCOHOL

The orientation of crystalline and noncrystalline chains under the swelling state of uniaxially stretched PVA dyed with Congo Red, was studied by x-ray diffraction, visible dichroism and birefringence as a function of deformation ratio. The following results were obtained: 1) For the specimen swollen at a released state, it was found that the film shrinkage results from the release of tension in noncrystalline chain caused by swelling. 2) For the specimen swollen at a stretched state, the change of orientation after the swelling is yielded from the increasing degrees of freedom of motion of noncrystalline chain in the swelling state. 3) Except in the necking regions, the noncrystalline orientation factor evaluated from the visible dischroism agrees with that calculated by assuming the additivity of birefringences of the crystalline and noncrystalline phases.