Natural rubber blends with epoxidized natural rubber

Blends of NR with ENR have been prepared in full composition following the polymer blend technique. Basic properties (mastication behavior and thermal degradation of each rubber and Mooney viscosity, Flory-Huggins interaction parameters, and cure characteristics of the blends) of the uncured blends were determined, in addition to the reversion, cross-linking density, mechanical and dynamic mechanical properties, rebound, and solvent swell of the blend vulcanizates. It was found that the NR/ENR blends are immiscible, showing two glass transition temperatures (T-g's) that showed outward migration in the blends. This was interpreted in terms of preferred migration of the curatives into the ENR phase. Retention of mechanical properties on aging, solvent resistance, and heat buildup were greater in NR-rich blends due probably to the higher cross-link density of the blends.