Epoxy‐resin‐cured carboxylated nitrile rubber

Curing of carboxylated nitrile rubber (XNBR) with epoxy resin in presence of different fillers has been studied. It was observed that 7.5 phr of resin give a compromise combination of properties in FEF black (N 550)‐filled vulcanizates at 40 phr loading. Further studies at different loadings of black, reinforcing silica and clay were done at 7.5 phr resin. Technical properties at different filler loadings have been determined. Polymer‐filler interaction involving FEF black, silica, and clay was examined by a Kraus plot and the equation of Lorenz and Parks. Silica and carbon black give a similar type of reinforcement, but clay shows nonreinforcing characteristics. In the case of carbon black–XNBR system, polymer‐filler attachment is similar to that existing in carbon black–natural rubber system. In the case of silica, reaction of the silanol group with the epoxide group of the epoxy resin and the carboxyl group of the base polymer may be responsible for the polymer‐filler attachment. Scanning electron microscopy (SEM) studies of the fracture surfaces corroborate the findings on technical properties and polymer‐filler interaction.