Blends of polypropylene (PP) and silicone masterbatch (SMBPP)-a commercial formulation consisting of an ultrahigh molecular weigh polydimethylsiloxane (PDMS) dispersed in PP-were prepared by melt mixing in an internal mixer. Four binary blends with different SMBpp content and two ternary blends containing silane-grafted polypropylenes (PP-VTES) of different VTES content as compatibilizer were produced. The blends were analyzed by melting flow rate, rotational rheometry, scanning electron microscopy, and differential scanning calorimetry (DSC). In all blends, the SMBpp remained as dispersed phase in the continuous PP matrix. The addition of PP-VTES reduced significantly the size of the SMBpp domains. Rheological and morphological data strongly indicate that the PP-VTES acts only by lowering the interfacial tension of the system without generating strong interaction between SMBpp domains and the PP matrix. The dimensions of the SMBpp domains and the interfacial energy were observed to determine the characteristics of the pseudoplastic behavior of the blends in the melt state. For both binary and ternary blends, the SMBpp domains showed nucleating effect leading to an increase of the degree of crystallinity. However, the decrease in the interfacial energy and viscosity promoted by the addition of PP-VTES to the system led to a more intense nucleating effect and to an increase of crystallization, melting temperatures, and melting enthalpy. (c) 2007 Wiley Periodicals, Inc.