Stabilizer system, dehydrochlorination

The beneficial effects of these systems were not observed for the NA-22 crosslinked CPE. Without the stabilizers and antioxidants a high maximum rate of dehydrochlorination of 140x10 mg. eq. HCl/g. polymer-hour was measured cund with these stabilizing additives the maximum rat of dehydrochlorination rose to a higher value namely 150x10. It is apparent that this... 

PVC heat stabilizers are used to protect polyvinyl chloride against thermal dehydrochlorination during processing and during use above room temperature. Similar additives are sometimes useful in other halogenated systems as well. 

Blends of polychloroprene with PMMA do not show the chlorine radical migration effects observed in PVC/PMMA blends, nor the stabilization of the dehydrochlorination reaction, both of which are consistent with the nonradical mechanism proposed for HCl production in the former polymer, but there is a major effect of HQ in producing PMMA stabilization. Blends of PVC with PMMA also show the effect of HCl, but this is masked by the earlier destabilization due to Q radicals. Acetic acid from PVA also leads to anhydride rings in PMMA with similar effects. Blends of PVC with PVAC show mutual catalysis of the decomposition of each polymer by the primary decomposition product of the other. This is seen both in TVA studies similar to those illustrated for the PVC/PMMA system and from direct measurements of acid production, as illustrated in Figure 18, which show clearly the destabilization of each polymer. 

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