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 susp ension PVC samples, polymerized at temperatures between 26 and 84-degr ees-C. The reproducibility of the suspension polymerization process an d the importance of the polymerization temperature with respect to the macro- and microstructure is demonstrated. Quantitative examination o f the grain structure by small angle neutron scattering, Brunauer-Emme tt-Teller absorption technique, and mercury porosimetry clarifies the gradual increase of the specific surface on lowering the polymerizatio n temperature. A detailed WAXS study shows an increasing degree of cry stallinity on lowering the polymerization temperature, which can be as sociated with the corresponding increase of the syndiotacticity. Furth ermore, the presence of a polymerization history in the PVC powders wi th respect to the crystallinity is evidenced. This effect seems to be related to chain mobility restrictions during the polymerization proce ss and is determined by the difference between the polymerization temp erature and the glass-transition temperature (T(g)) of rigid PVC. This so-called T(g) effect is indicative of the fact that no appreciable s welling of PVC by its monomer occurs. (C) 1994 John Wiley & Sons, Inc.