Oil from poly(vinyl chloride): Unprecedented degradative chain scission under mild thermooxidative conditions

Surprising new results were obtained during our investigations on the thermooxidative degradation of poly(vinyl chloride) (PVC) in dioctyl phthalate, DOP (bis(2-ethylhexyl) phthalate, DEHP), at 200 °C, i.e., in the range of the processing temperature of PVC. Enhanced dehydrochlorination of the polymer was found in DOP on the one hand. It is a striking observation that oily products are formed after 3 h of reaction time, on the other hand. GPC measurements proved that severe chain scission with nearly constant rate occurs under the applied mild conditions. FTIR and NMR analyses revealed the oxidation of the main PVC chain and simultaneous attachment of DOP to the polymer backbone in the course of the radical chain reaction of this oxidative process. Both the partially oxidized PVCs at lower and the oily products formed at longer degradation times may open new routes for PVC recycling, such as broadening its blending possibility with other polymers and polymeric waste materials.