POLARON MECHANISM IN THE THERMAL STABILIZATION OF POLY(VINYL CHLORIDE) .1. METAL SOAPS AND SECONDARY STABILIZERS

In the thermal stabilization of PVC, it has been shown that, by contro lling the cis configuration of conjugated double bonds initially prese nt or developing in the polymer during the stabilization, the alkyl ch ains attached to stabilizers favor the substitution of the allylic chl orine atoms by an esterification reaction proposed by Frye et al. By i nteracting with the conjugated double bonds to form polarons which inh ibit the esterification reaction, the metal chloride leads to the chai n dehydrochlorination of the polymer by a process reported previously. As far as the synergism due to costabilization of the secondary stabi lizers and the metal soaps is concerned, we show that the efficiency o f a secondary stabilizer arises essentially from the blocking of the p olaron DHC to favor allylic chlorine substitution.