DEPENDENCE OF STRUCTURE OF DEHYDRATED PVA ON CRYSTALLINITY OF ORIGINAL PVA

In the reported investigation, PVA films having different crystallinities were prepared by elongating PVA films to different degrees and heating the films with and without elongation treatment at several temperatures between 60 and 200 degree C. Then, they were dehydrated by heating from 80 degree C to 230 or 330 degree C in hydrogen choride gas. IR spectral measurements were made on the dehydrated PVA films obtained. Absorbances of the absorption bands due to several groups seen in the IR spectra depended only on the density of original PVA films, regardless of its degree of elongation. From these dependences, it was found that the dehydration reaction progressed more easily in the crystalline region than in the amorphous region, that the aromatic rings with four or five adjacent hydrogen atoms were formed mainly in the amorphous region and those with two adjacent hydrogen atoms in the crystalline region, and that the aromatic rings with two isolated hydrogen atoms were formed in both the amorphous and crystalline regions.