Processing, Curing and After‐Cure Dynamic Properties of a Thermally Polymerizable Bismaleimide‐Filled Natural Rubber Formulation

ABSTRACT This work describes the processing, curing, and after‐cure dynamic properties of natural rubber/bismaleimide compositions in different ratios (100/0, 95/5, 90/10, 85/15, and 80/20). Each composition incorporates an accelerated‐sulfur cure system based on the rubber content to crosslink the rubber phase. The Mooney viscosity of the rubber composition significantly decreases as the content of bismaleimide increases from 10 to 20 phr. The rheological parameters—such as storage modulus ( G' ), loss modulus ( G“ ), and tan δ ( G“/G' ), of the bismaleimide‐containing compositions obtained from a 2‐point frequency sweep test as per ASTM D6204 Part B, indicate that the addition of bismaleimide can enhance processability. The reduction in the dynamic viscosity ( η ) of the composition containing bismaleimide further endorses why the Mooney viscosity decreases as the content of bismaleimide increases in the compositions. A cure‐after‐cure strain sweep test performed at 160°C for different times as per ASTM D6601 exhibits a higher G' for the bismaleimide‐filled composition. This experimental observation leads to a strong assumption that the bismaleimide in the composition polymerizes at 160°C and interpenetrates into the sulfur‐crosslinked network structure, making it more resistant to dynamic deformations.