Thermal degradation of plastisols. Effect of some additives on the evolution of gaseous products

Direct inlet mass spectrometry (DIMS) has been applied to some combinations based on a PVC resin (Vestolit 7021, HULS), one plasticizer (DEHP) and two stabilizers (Ba-Zn stearate and octadecyl-3-(3,5-tert-butyl-hydroxypheny)-propionate). Two different resin/plasticizer ratios and five different stabilizer concentrations have been studied. A comparative study of TIC curves and mass spectra between those different formulations has been developed. A wide peak at low temperatures corresponding to plasticizer vaporization has been observed, and the dehydrochlorination peak has been quantified in order to know the evolved products, mainly HCl. Benzene and alkyl-aromatics have also been observed and quantified for every formulation. In addition, some typical peaks corresponding to additives have been identified, and these have been used to know the stabilization behavior of every compound. When octadecyl-3-(3,5-tert-butyl-hydroxyphenyl) -propionate is used as stabilizer, it appears to be a better product to stabilize plastisols (dehydrochlorination peaks are lower). Hence we can conclude that this metal carboxylate (known for its environmental toxicity) could be replaced by new products that are better environmentally. (C) 1997 Elsevier Science B.V.