AbstractHNBR rubbers, which are made by selective hydrogenation of the olefinic bonds of NBR rubbers, have been developed, because they show improved resistance towards heat and chemicals. In this study, two other properties are discussed that arise from the fact that HNBR rubbers are fairly alternating copolymers of unpolar butylene and polar acrylonitrile units: At intermediate compostions, HNBR rubbers form homogeneous blends with PVC, and near the symmetric composition they exhibit strain‐induced crystallisation. The thermal transitions of the HNBR rubbers and their miscibility with PVC were analyzed, as well as the crystallisation and the stress‐strain behaviour of a HNBR of symmetric composition.