Structure and some physical properties of polyvinyl chloride polymerized at different temperatures

Abstract

Abstract In discussing the structure of polyvinyl chloride as a function of the polymerization temperature, the effect of the stereoregularity and the branching should be principally taken into consideration. In the present work, in order to investigate the effect of the polymerization temperature on these two structural factors, both the degree of branching and the stereoregularity were determined on polyvinyl chloride samples polymerized at 90, 50, 20, −15, and −75°C., and these two factors were related to the physical properties such as density, crystallinity, glass transition temperature and melting temperature. It was found that, with decreasing polymerization temperature, the degree of branching decreased from 0.27 (CH 3 /100 CH 2 ) for sample polymerized at 90°C. to zero (CH 3 /100 CH 2 ) for sample polymerized at –75°C., whereas, the stereoregularity increased from 0.51 for sample polymerized at 90°C. to 0.77 for sample polymerized at –75°C. Density, crystallinity, glass transition temperature and melting temperature were increased as the polymerization temperature was lowered. It may be concluded that the syndiotacticity of the polymer, especially for samples polymerized at lower temperatures, may contribute principally to the physical properties of the polymer.