Structure and drawability of gel films from formalization of high molecular weight poly(vinyl alcohol) aqueous solution

Abstract

In this work, the structure and drawability of dried formalized gel films prepared from the formalization of high molecular weight polyvinyl alcohol (PVA) aqueous solutions were studied. Structure changes in PVA crystal were found in the formalized samples, i.e., the spacing of the (100) plane for PVA crystal became much larger while that of the (020) plane became smaller, indicating that some disordered crystals were formed from formalized PVA chains. The crystal relaxation temperature, T_αc, and its dependence on the draw ratio in formalized films were lower than those in original the PVA. Irrespective of the lower crystalline properties and the crystal relaxation temperature, the drawability of formalized PVA films could not be improved. The crystal orientation function, f_c, decreased as the degree of formalization at a given draw ratio was increased, indicating that the acetal groups in the amorphous region must be a hindrance to the drawing of the formalized PVA. These results implied that the drawability of PVA is not only related to the properties of the crystalline region but also to those of the amorphous region.