The evaluation of an innovative costabiliser for poly(vinyl chloride) .2. Interactions between metal stearates and the costabiliser

The interaction of a novel triketone costabiliser for poly(vinyl chloride)(PVC), with metal stearate stabilisers (Ca and Zn) has been evaluated with a view to understanding the mechanism responsible for its outstanding performance in inhibiting discolouration in this polymer. Combinations of the triketone costabiliser and the metal soaps were compared when mixed and when heated. Changes in the mixtures were followed by FTIR and luminescence spectroscopy. For comparison, the method was repeated using dibenzoyl methane (DBM) and dehydroacetic acid (DHA) as costabilisers for the metal soaps. The triketone exhibited a remarkable ability to form coordination compounds with the metal soaps, even on simple mixing. On the other hand, DBM and DHA did not show any notable behaviour in this respect requiring processing temperatures before formation of relatively small amounts of coordination species. Stabilisation mechanisms have been considered on this basis. (C) 1996 Elsevier Science Limited.