Polypropylene (PP) was blended with polyoxyethylene nonylphenol (PN) in a twin-screw extruder and injection moulded. The dynamic mechanical properties of PP/PN blends were characterized by dynamic mechanical analyser (DMA). The glass transition temperature (T-g) of PP showed a slight decrease with incorporation of PN. Differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarized optical microscopy (POM) were employed to investigate the effects of PN on crystallization of PP. In a study of nonisothermal crystallization of PP and PP/PN blends, crystallization parameter analysis showed the addition of PN reduced the peak temperature of crystallization. beta-form crystals of PP coexisted with alpha-form crystals in PP/PN blends, and oriented on the surface layer of injection moulded bar as revealed by WAXD. The degree of orientation was determined using Hermans orientation function. The thermal stability of beta-form crystals was evaluated using high temperature WAXD and POM. (c) 2005 Elsevier Ltd. All rights reserved.