Study of discolouring change in PVC, plasticizer and plasticized PVC films

Plasticized and non-plasticized PVC films discolour on photochemical attack. We have used UV analysis to study the separate contributions of PVC and plasticizer to discolouring in plasticized PVC. As has already been demonstrated, photochemical degradation leads to the browning of PVC films due to the formation of polyenes and the degradation is accelerated by the presence of THF used in the preparation of the films. It is shown in this study that plasticizer films turn yellow, but that THF does not play a role in their degradation, and that the plasticized PVC films become dark yellow on UV exposure. Therefore, it appears that the plasticizer contributes to the discolouring change of the plasticized PVC not only by its influence on the PVC, as has been shown in many studies, but also by its own discolouration. (C) 1997 Elsevier Science Limited.