The Effect of Phthalate/Sulphonic Acid Ester Plasticisers on the TiO2 Photocatalyzed Degradation of PVC

Abstract

The effects of two plasticizers, one phthalate and one sulfonic acid ester, on the photodegradation of TiO2 pigmented polyvinylchloride (PVC) films are reported. The loading of each plasticizer was altered in the range 0 - 70% relative to the PVC and the effects on the rates of photomineralization were determined using a closed loop flow system to detect the carbon dioxide evolution. All plasticizer additions lead to an initial acceleration in CO2 evolution over the non-plasticized cases. Non-plasticized films show a marked acid catalysis due to HCl evolution which leads to an acceleration in the rate of oxidation with time. Following initial rapid oxidation of pre- adsorbed plasticizer, the phthalate systems demonstrated a reduced rate of CO2 production and no acid catalysis. The sulfonic acid ester plasticizer is broken down to produce sulfonic acid and sulfuric acid fragments which are sufficiently acidic to catalyze the TiO2 when plasticizer loadings are >50%. The carboxylic acid fragments from the phthalates seem incapable of catalysis even at the highest levels used in this work.