Curing of epoxidized natural rubber with p‐phenylenediamine

The curing of epoxidized natural rubber with p‐phenylenediamine catalyzed by bisphenol A was investigated. The curing reaction was found to be first order with respect to the amine and to have an activation energy of 67.5 kJ/mol. Vulcanizates of tensile strength 12.5–16.0 MPa were obtained at cure times of 30–75 min at 180°C. The amine‐cured vulcanizate was observed to be more rigid than the sulfur‐cured one at room temperature consistent with its relatively high Tg. Stress‐strain analysis and dynamic mechanical properties indicated that the high Tg of the amine‐cured vulcanizate could be attributed to the bulky amine crosslinks and hydrogen bonding effect of bisphenol A.