습식 연신 공정에서 팽윤조건이 PVA 필름의 구조 변화에 미치는 영향에 관한 연구

Abstract

The effects of swelling conditions in water on the orientation and crystallization behavior of non-oriented polyvinyl alcohol (PVA) films were investigated in terms of swelling temperature and swelling time. As a reference material the nonpolar polypropylene (PP) films of similar thickness were used. The crystal structure and micro-morphology of the wet-drawn films were studied by wide angle X-ray diffraction. As swelling temperature was increased the water content of PVA films was increased but the degree of crystallization was decreased without the change of the average crystal size. But, an abrupt increase of the water content was observed between 40 and 50 oC. The water content was leveled off after ca. 100 s. At 50oC, however, it was decreased after ca. 200 s. Thermal analysis of the PVA films revealed that the peaks of water evaporation shifted to higher temperature and got sharper with increasing swelling temperature. However, the intensity of specific peak for oriented PP films decreased but that all crystalline peaks for oriented PVA films were rapidly increased as draw ratio was increased.