Chemorheological treatment of crosslinked EPT

Abstract

Abstract Stress relaxation mechanisms were investigated on three types of (EPT) ethylene–propylene terpolymers in air at 109°C. These polymers differe only by the structure of the crosslinkage in which there is a carbon–carbon bond, a polysulfide linkage (S◯) or a monosulfide linkage (S). All the stress relaxation of peroxide‐cured EPT polymer was not due to the oxygen‐induced cleavage of the main chain but to a physical flow. In the case of sulfur‐cured EPT polymer, the relaxation curve is divided into three straight lines when the procedure X is used and log f ( t )/ f (0) is plotted linearly with time. It was concluded that this graph was in agreement with an interchange reaction of the polysulfide linkage by an oxidative cleavage of the monosulfide linkage. On the other hand, a TT‐cured EPT polymer gave a plot with a straight line. This stress relaxation could be explained by an oxidative cleavage of the monosulfide linkage.