DERIVATOGRAPHIC STUDY OF COPOLYMERS OF ISOBUTYLENE WITH alpha -METHYLSTYRENE AND DICYCLOPENTADIENE.

One of the most important service indices characterizing polymer-based additives is the resistance of these additives to depolymerization in the compounded oils. As is well known, polyisobutylene, which is used widely for this purpose, is not very resistant to thermal or mechanical breakdown, so that oils compounded with polyisobutylene will often show rather considerable decreases in viscosity during service. However the copolymers of isobutylene with alpha -methylstyrene or with dicyclopentadiene have been shown to have improved thermal stability as compared with homopolymer. This paper reports results of thermogravimetric studies of these copolymers. Also included in this study was the influence of mol wt and copolymer composition on the thermal stability. It is concluded from data obtained that the thermal stability of these compounds, for a given level of mol wt, increases in the following order: polyisobutylene, isobutylene/dicyclopentadiene copolymer, and isobutylene/ alpha -methylstyrene copolymer.