A 119Sn Mössbauer study of the thermal degradation of organotin stabilisers in PVC

119mSn Mössbauer studies of the thermal degradation of PVC containing the stabilisers dibutyltinbis (isooctylthioglycollate) (1.2% by weight of the polymer), dioctyltinbis (isooctylthioglycollate (4% by weight of the polymer) and dibutyltinbis (isooctylmaleate) (2% by weight of the polymer) indicate that in each case the stabiliser is converted into the dialkylmonochlorotin ester R2SnCl(X) (X  SCH2CO2C8H17or O2C.CH  CHCO2C8H17), and not into the dialkyltin dichloride, R2SnCl2, as recently suggested by other workers. Comparison of the Mössbauer data for organotin-stabilised PVC samples prepared by both hot-milling and room temperature solvent casting processes indicates that there is little degradation of the polymer (and stabiliser) during the initial hot-milling process.