Structure and Property of Medium-Oriented Polyoxymethylene by Press Elongation Method
Kenji TAKASA, Norikazu MIYASHITA, Shun-ichi TACHIBANA and Kunihiko TAKEDA
Abstract:The physical structure of oriented polyoxymethylene (POM) was studied, and the degree of crystallization and tensile modulus depending on stretching ratio were analyzed. The oriented films were obtained through 2-directional stretching using press elongation method. The stretching ratio reached to 6.0, and the tensile modulus increased from 2.5GPa to 4.5GPa. However, the degree of crystallization slightly decreased from 70% to 65%. The rupture elongation increased in the lower stretching region and reached its peak when the stretching ratio was 1.7%. The characteristics of the physical structure such as the degree of the crystallization and the orientation and dispersion of the lamella were analyzed by measuring the density and the X-ray diffraction. The crystal orientation observed by the X-ray diffraction pattern was isotropic, and the result was confirmed by microscopic photos. The crystallization was found out to be difficult under strong mechanical strength. After thermal aging under various temperatures, the degree of the crystallization increased from 63% to 67%. However, a degree higher than 67% could not be observed. The major factors of such a complicated phenomena seemed to be the higher rate and degree of crystallization of POM than those of PET. Key Words:Polyoxymethylene, Film, Elongation, Orientation, Press, Crystallinity