Studies of the thermal stability of poly (vinyl chloride). I: Influence of light on the thermal stability of PVC

Abstract The molecular structural defects in four suspension-polymerized poly(vinyl chloride) (PVC) samples and their thermal dehydrochlorination rates in light and dark were determined quantitatively. Based on the influence of light, especially u.v., on the thermal stability of PVC, it is concluded that the rate of thermal dehydrochlorination of PVC in the dark is related to the labile chlorine atoms (particularly internal allylic chlorine atoms), while the rate of photo-thermal dehydrochlorination of PVC in light is related to the carbonyl allylic groups and the double bonds (particularly terminal double bonds). A radical mechanism for the thermal dehydrochlorination (two steps) and the photo-thermal dehydrochlorination (three steps) is proposed.