Evaluation of oriented amorphous regions in polymer films during uniaxial deformation; structural characterization of a poly(vinyl alcohol) film during stretching in boric acid aqueous solutions

Abstract

We have improved the conventional analytical method of the scattering data obtained with in-situ synchrotron X-ray scattering experiments, which is applicable to the structural characterization of the film during stretching. Four components of molecular chains in the film are divided from two-dimensional wide-angle X-ray diffraction patterns. These components are the oriented crystals, the unoriented ones, the oriented amorphous chains, and the unoriented ones, respectively. This method allows to evaluate directly the degree of orientation of the amorphous chains and the amount of the oriented amorphous fraction in addition to each evaluation for the crystalline regions. This method is applied to the structural characterization of the poly(vinyl alcohol) (PVA) film during stretching in boric acid aqueous solutions, suggesting that boric acid accelerates orientation of molecular chains in the amorphous regions, and increases the oriented amorphous fraction by producing the cross-links between the PVA chains and hindering strain-induced crystallization. At a film break on stretching in the 3 wt% boric acid solution, the oriented amorphous fraction increases up to 70%, which is much higher compared to that in the film stretched in water, 45%. POLYM. ENG. SCI., 55:513–522, 2015. © 2014 Society of Plastics Engineers