Analysis of UV induced dehydrochlorinated PVC (With hydroquinone) using direct pyrolysis mass spectrometry (DPMS), TGA, UV/VIS-NIR and FTIR techniques

Abstract

Poly(vinyl chloride) (PVC) degrades easily upon heat and light exposure via loss of HCl. The mechanism of this process is well understood, known as the zip mechanism and the dehydrochlorination results in conjugated segments, polyenes. It is also possible to utilize PVC polymer as an in-situ acid donor since the main degradation product is HCl. Addition of hydroquinone (HQ) into PVC matrix sensitizes the photodehydrochlorination of PVC at 312 nm. In this study the effects of photodehydrochlorination on thermal and material properties of PVC were investigated using DPMS and TGA as well as UV-Vis-NIR and FTIR techniques. In addition, the photodegradation of PVC/PVAc blend, copolymer (PVC-coPVAc) and PVAc were similarly investigated. Dehydrochlorination of the polymers resulting from UV-exposure were also investigated for doping of PANI in blends. HCl evolution behavior of the UV dehydrochlorinated PVC exhibits a characteristic property which is different from the unirradiated ones. Both DPMS and TGA results confirms the sensitization of PVC photodehydrochlorination at 312 nm by hydroquinone (HQ) resulting in a temperature onset that is the lowest (140 oC). HQ assistance upon 312 nm UV exposure is not significantly observed in the copolymer. The low temperature onset of UV-induced copolymer is a promising result to produce longer polyene chains, since polymer backbone starts to decompose after ca. 220 oC, using copolymer might be an alternative to PVC.