The effect of chopped rice husk (CRH) content on viscoelastic properties and crystallinity of polypropylene (PP) composites was investigated. Composites containing 0, 20, and 40 part per hundred plastics (php) of CRH into PP were prepared by twin-screw extruder, with maleic anhydride-grafted PP as the coupling agent. The viscoelastic behavior and the crystallinity of these composites have been studied by dynamic mechanical analysis as well as differential scanning calorimetry, respectively. By the incorporation of CRH into PP, the storage modulus (E') was found to be increased progressively, whereas the mechanical loss factor (tan 6) decreased in a nonlinear manner. A self-consistent analysis was proposed for the prediction of viscoelastic response of the interphase between PP matrix and CRH particles. A three-phase model was applied in a reverse mode, and the viscoelastic behavior of the interphase was extracted and compared with the unfilled matrix. Differential scanning calorimetry results indicated that CRH influences crystallization temperature as well as the degree of crystallinity of the composites. An entrapped polymer within CRH filler and PP matrix was detected by scanning electron microscope, which can be attributed to the interfacial layer with a good adhesion between the main components. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1642-1651, 2011