Glass transition and melting point of poly(vinyl chloride)

Abstract

AbstractBoth the glass transition temperature and the melting point of poly(vinyl chloride have been found to increase as the temperature at which the ample is polymerized is decreased). The glass transition temperature changes from about 70°C. for polymer prepared at 125°C. to about 100°C. for polymer prepared at −80°C. It is believed the increase in percentage of syndiotactic structure which results from decreasing the polymerization temperature is responsible for the change in glass transition temperature. The effect of polymerization temperature on melting point is even more striking. The melting point changes from approximately 160 to above 300°C. on lowering the polymerization temperature from 125 to −80°C. X‐ray diffraction studies show that polymers prepared at low temperature form crystals which have a substantial increase in perfection along the chain axis. It seems probable that this increase in crystalline perfection along the chain axis is responsible for the very marked increase in melting point.