The melting and crystallization behaviors of isotactic polypropylene (PP)/acrylonitrile-butadiene rubber (NBR) blends were investigated with differential scanning calorimetry. The samples were scanned at a heating rate of 20 degrees C/min in a nitrogen atmosphere. The effects of blend ratio, compatibilizer, and filler addition on the melting and crystallization characteristics of the blends were analyzed. Analysis showed that blend ratio had a predominant effect on the values of onset of crystallization and crystallization temperature, although the heat of fusion (Delta H-f), onset of melting, and melting temperature were unaffected. The presence of compatibilizer in the blend had an appreciable influence on the crystallization behavior. Delta H-f, heat of crystallization, and percentage crystallinity of the compatibilized blends were higher than those of the uncompatibilized blends. Fillers had little impact on the melting behavior of the blends. The morphology of the blends were analyzed with scanning electron microscopy. Hot-stage polarizing optical microscopy was used to study the spherulitic morphology of PP on the addition of NBR. The addition of a few percentage NBR significantly reduced the average spherulite size of PP in the blend followed by a marginal decrease. Blend ratio had a pronounced impact on the growth rate of PP spherulites. (c) 2006 Wiley Periodicals, Inc.