Nitrilic rubbers containing 29 or 45% of acrylonitrile were blended with polyaniline doped with different acids (chloridric, dodecylbenzenesulfonic, tetrapropylbenzenesulfonic, and p-toluenesulfonic acids). The blends were prepared by mechanical mixing in a roll-mill and vulcanized in a hot press. The volumetric conductivities and mechanical properties were evaluated. The results show that the polyaniline concentration strongly affects the behavior of the blends. Increasing the polyaniline content from 50 to 100 phr induces an increase in the electric conductivity from 10(-10) to 10(-8) S cm(-1); however, the blends become harder and more brittle than the crude rubber. Addition of polyaniline lowered the crosslinking degree, but produced a reinforcing effect in the elastomer. (C) 2000 John Wiley & Sons, Inc.