Very low-density polyethylene (VLDPE) was compounded with polypropylene (PP) to improve its impact strength. VLDPE was modified by grafting 3-(trimethoxysilyl) propyl methacrylate silane (MS) to VLDPE to prepare mVLDPE. PP was melt-mixed either with VLDPE or mVLDPE together with Cloisite (R) 20A (C20A). The composites exhibited a phase-separated morphology, irrespective of whether the VLDPE had been modified with the silane compounds or not. Incorporation of C20A decreased the domain size of the dispersed phases of both PP/VLDPE and PP/mVLDPE blends. The tensile strength and elongation at break of PP/VLDPE and PP/mVLDPE were improved by the addition of C20A. In contrast, their impact strengths were reduced by the clay. However, the decrease in impact strength was less significant in PP/mVLDPE/C20A than in PP/VLDPE/C20A. The superior mechanical properties of PP/mVLDPE/C20A over PP/VLDPE/C20A were attributed to enhanced interfacial interactions originating from chemical reactions between silane residues on mVLDPE and the silanol groups of C20A. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 35473552, 2011