THE EFFECT OF PHTHALATE/SULFONIC ACID ESTER PLASTICIZERS ON THE TiO{sub}2 PHOTOCATALYZED DEGRADATION OF PVC

摘要

The effects of two plasticizers, one phthalate and one sulfonic acid ester, on the photodegradation of TiO{sub}2 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 CO{sub}2 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 CO{sub}2 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 TiO{sub}2 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.