The thermal stability of isotactic polypropylene (PP)/nitrile rubber (NBR) was studied using thermogravimetry. The effects of blend ratio, compatibilisation and dynamic vulcanisation on thermal stability were investigated. The addition of nitrile rubber to polypropylene was found to improve the thermal stability of polypropylene. The compatibilisation of the blends using phenolic modified polypropylene and maleic anhydride modified propylene has increased the degradation temperature and decreased the weight loss. The dynamic vulcanisation of the blends also improved the thermal stability. The melting behaviour was investigated by differential scanning calorimetry for the binary blends. The crystallinity of the blends decreased with increase in NBR content. The crystalline structure of the blends was investigated using wide angle X-ray scattering. The polypropylene and the blends exist in the or-monoclinic form as shown by the presence of four maximas. The compatibilisation of the blends did not affect the ol-monoclinic crystalline structure. The addition of NBR to polypropylene increased the interplanar distance. (C) 2000 Elsevier Science Ltd. All rights reserved.