STABILIZATION OF POLY(VINYL CHLORIDE) WITH PREHEATED METAL STEARATES AND COSTABILIZERS - I - USE OF A BETA-DIKETONE

The influence of a beta-diketone on the already observed anomalous beh avior of preheated metal stearates as stabilizers for PVC has been eva luated. During normal stabilization procedure, the addition of diketon es reduce the stabilization times, but the pretreatment of the mixture of metal soaps or of the individual zinc soap (then added to the calc ium soap) delayed such times, recovering to some extent the reduction induced by the costabilizer. The calcium soap preheated (added along w ith zinc stearate to PVC), on the other hand, reduced the induction ti mes further. These findings obtained by measurement of induction times by means of loss of weight (TGA) and HCl evolution, have been support ed by FTIR and visible reflectance studies. While using preheated ZnSt (2), a second rate of dehydrochlorination was observed in the HCl evol ution traces, suggesting a separate consumption of the compounds durin g the stabilization mechanism. In general, it can be said that preheat ed primary stabilizers and costabilizers have no significant interacti ons between them. The final result is just the addition of their separ ate effects. (C) 1998 John Wiley & Sons, Inc.