Abstract: The heat stabilization of several mercaptans and thiophenols on PVC was determined by the oven discoloration method. It was found that their heat stabilizing capacity improved with increasing of the positive electricity of the α-C atom and decreasing of the strength of the S—C bond in the molecules. According to this finding it could be speculated that mercaptans and thiophenols stabilize PVC by electrophilic reaction with PVC using their α-C atom as the electrophilic centers. This meant that the traditional Frye and Horst’s theory of heat stabilization did not apply to mercaptans and thiophenols, and therefore, the exact mechanism of heat stabilization of heat stabilizers need to be clarified by further research.

Key words: mercaptan, thiophenol, poly(vinyl chloride), thermal stabilizer, heat stabilization, progressive change law of performance, mechanism