Hydrotalcite additions (up to 10 PHR) are shown to stabilise unplasticised polyvinylchloride (UPVC) against TiO 2 photocatalysed degradation. Without stabilisation, hydrogen chloride, produced through dehydrochlorination, catalyses the TiO 2 sensitised degradation after a set period of reaction leading to an increase in rate from 13 to 32 mmol m 22 min 21 . Hydrotalcite removes chloride by anion exchange releasing carbonate ions in the PVC removing this autocatalytic pathway.
The effects of two plasticisers, one phthalate and one sulphonic acid ester, on the photodegradation of TiO 2 pigmented polyvinylchloride films are reported. The loading of each plasticiser was altered in the range 0-70% relative to the polyvinylchloride and the effects on the rates of photomineralisation were determined using a closed loop flow system to detect the carbon dioxide evolution. All plasticiser additions lead to an initial acceleration in CO 2 evolution over the non-plasticised cases. Non-plasticised 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 preadsorbed plasticiser, the phthalate systems demonstrated a reduced rate of CO 2 production and no acid catalysis. The sulphonic acid ester plasticiser is broken down to produce sulphonic acid and sulphuric acid fragments which are sufficiently acidic to catalyse the TiO 2 when plasticiser loadings are .50%. The carboxylic acid fragments from the phthalates seem incapable of catalysis even at the highest levels used in the present work.
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.
Hydrotalcite additions (up to 10 PHR) can stabilize un-plasticizedpoly-vinyl-chloride against TiO 2 photo-catalyzed degradation. Without stabilization, hydrogen chloride, produced through dehydrochlorination, catalyses the TiO 2 sensitized degradation after a set period of reaction leading to an increase in rate from 13 μmol m -2 min -1 to 32 μmol m -2 min -1 . Hydrotalcite removes chloride by anion exchange releasing carbonate ions in the PVC removing this autocatalytic pathway. Hydrotalcite performs very well in comparison to commercial Barium/Zinc salt stabilizers.
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