Effect of Hydrogenation and Chlorination Reactions on the β Relaxation of Poly(Vinyl Chloride)

The relaxation phenomena of polymers are very important because they play an important role in their physical properties. Dynamic mechanical analysis was used in this work in order to study the effect of tactic and compositional sequences on the relaxation processes observed in poly(vinyl chloride) (PVC). The polymers studied in this work were PVC modified by means of reductive hydrogenation and chlorination reactions at low degrees of modification. The results obtained with hydrogenated poly(vinyl chloride) indicated that the decrease in mmr tetrads at the end of the isotactic sequences in the chain by stereospecific hydrogenation led to concomitant decreases in intensity and temperature of the maximum of the β relaxation. This effect seemed to be stronger the longer the isotactic sequence associated with the said structure. On the other hand, in the case of chlorinated poly(vinyl chloride) (CPVC), the results of the evolution of the β relaxation with the degree of chlorination showed that the predominant factor was the compositional microstructure (substitution of hydrogen atoms by chlorine atoms, increasing the possibility of inter-chain interactions leading to a stiffening of the chain, with the consequent increase in the β temperature)