Chemorheology of EPR

Abstract

EPR was cured with Dicumil peroxide (1), the combination of Dicumil peroxide and p-Quinone-dioxime (2), Dicumil peroxide and Trichloromelamine (3), and Dicumil peroxide and Sulfur (4) at 150°C. Then we observed the mechanism of degradation of those materials by the methods of stress relaxation. It is considered that (1), (2), and (3) caused scission reactions of the links of network chains, but (4) caused scission at both of the network polymer chains and crosslink sites. The degradation owed for its main factor to the amount of peroxides in those materials.
It is found out that the heat stress relaxation of vulcanizates was accelerated by substances that were soluble in acetone contained in EPR and the curing agents in vulcanizates that had not yet been subjected to reaction. The vulcanizates extracted with benzene relaxed more slowly than those extracted with acetone. Considering the degree of swelling by benzene (larger than by acetone), it seemed that the amount of the curing agents etc. extracted from vulcanizates with benzene and had not yet been subjected to reaction was larger than that extracted with acetone and that resulted in the above phenomena.
On the other hand, (3) extracted with acetone relaxed more slowly than that extracted with benzene, and this will be accounted for by the fact that Trichloromelamine was soluble in acetone but almost insoluble in benzene.
The comparison of stress relaxation between commercial EPR and refined EPR revealed that the relaxation or degradation was accelerated when EPR contained some hydrocarbone that was soluble in acetone.