A model waste nitrile rubber powder (w-NBR) was prepared by ambient grinding of aged NBR vulcanizate based on an oil seal formulation. The w-NBR was characterized by scanning electron microscopic and optical microscopic techniques. Virgin nitrile rubber in a thermoplastic elastomeric 70:30 nitrile rubber/poly(styrene-coacrylonitrile) (SAN) blend was replaced by w-NBR, and the mechanical properties and swelling index were determined. The virgin NBR in the blend was replaced by the rubber present in w-NBR (r-w-NBR) and the optimum mechanical properties were achieved at 45% replacement where the blend was still reprocessable. Transmission electron microscopic and atomic force microscopic studies reveal that w-NBR particles coated with NBR are dispersed in a continuous SAN matrix. It was observed that migration of unreacted curatives from w-NBR to virgin NBR is not significant and incorporation of curatives is necessary for attainment of optimum level of mechanical properties. (C) 2003 Wiley Periodicals, Inc.