The evaluation of an innovative costabiliser for poly(vinyl chloride)—I. Inhibition of discolouration and stabilisation performance in the polymer

The stabilisation performance of a recently patented triketone costabilser for poly(vinyl chloride) (PVC) in the presence and absence of zinc and calcium stearates has been evaluated. By way of comparison two other costabilisers, dibenozyl methane and dehydroacetic acid, have also been investigated. Although all three costabilisers reduce the induction time to degradation of PVC (in comparison to when the metal stearates are used alone), they also reduce discolouration of the polymer during degradation. In particular, the triketone exhibits outstanding inhibition of discolouration. Observations from both infra-red and luminescence spectroscopy suggest the costabilisers coordinate with the metal soaps. The extent of coordination apparently controls the point in the degradation mechanism when the costabilisers are able to interact with those labile structures which otherwise lead to colour formation.