STRUCTURAL ASPECTS OF SUSPENSION POLY(VINYL CHLORIDE) - INFLUENCE OF TEMPERATURE ON THE MACROSTRUCTURE AND MICROSTRUCTURE

The structural aspects of rigid suspension poly (vinyl chloride), PVC, have been investigated on the basis of two independent series of suspension PVC samples, polymerized at temperatures between 26 and 84-degrees-C. The reproducibility of the suspension polymerization process and the importance of the polymerization temperature with respect to the macro- and microstructure is demonstrated. Quantitative examination of the grain structure by small angle neutron scattering, Brunauer-Emmett-Teller absorption technique, and mercury porosimetry clarifies the gradual increase of the specific surface on lowering the polymerization temperature. A detailed WAXS study shows an increasing degree of crystallinity on lowering the polymerization temperature, which can be associated with the corresponding increase of the syndiotacticity. Furthermore, the presence of a polymerization history in the PVC powders with respect to the crystallinity is evidenced. This effect seems to be related to chain mobility restrictions during the polymerization process and is determined by the difference between the polymerization temperature and the glass-transition temperature (T(g)) of rigid PVC. This so-called T(g) effect is indicative of the fact that no appreciable swelling of PVC by its monomer occurs. (C) 1994 John Wiley & Sons, Inc.