Silicate layer exfoliation processes in maleic anhydride (MA) modified polyolefins were studied by using X-ray diffraction measurements, scanning electron micros-copy, and transmission electron microscopy observations. Modified polyolefins grafted with 0.09-4.5 wt % MA groups intercalate into the organophilic clay galleries modified with stearyl ammonium ions. Molten MA-modified polypropylene continuously intercalates into the galleries and the silicate layers exfoliate spontaneously without shear. However, the silicate layers maintain arranging parallel together, although the interlayer spacing expands over 10 nm. By adding shear, the silicate layers homogeneously disperse into MA-modified polypropylene matrix. (C) 2004 Wiley Periodicals, lnc.