AbstractThe effect of polymers with conjugated bonds, namely polyphenylvinylene, phenylacetylenep‐diethinylbenzene copolymer and thermally dehydrochlorinated polyvinylchloride, upon the stability of polyvinylchloride suspensions has been investigated. It has been shown that polymers with conjugated double bonds are efficient inhibitors of the thermal dehydrochlorination of polyvinylchloride. The most active inhibitor, polyphenylvinylene, is not light stabilize