Mechanism of Action and Effectiveness of Ester Thiols as Thermal Stabilizers for Polyvinyl chloride)

摘要

Organic thiols containing at least one carboxylate ester group (ester thiols) are excellent thermal stabilizers for both rigid and plasticized polyvinyl chloride) (PVC).Their mechanism of action is shown to involve the deactivation of unstable structural defects by nucleophilic chloride displacement,the retardation and removal of coloration through thiol additions to polyene double bonds,and the prevention of autoac-celeration during thermal dehydrochlorination through polyene shortening reactions and the scavenging of free radicals formed from polyenes and HCI.An unusually facile displacement of labile chloride that is favored by thiol acidity can account,at least in part,for the relatively high effectiveness of dipentaerythri-tol hexakis(mercaptoacetate) as a stabilizer.