The melt-direct intercalation method was employed to prepare poly(propylene) (PP)-maleic anhydride grafted poly(propylene) (PP-g-MAH)-organic-montmorillonite (Org-MMT) nanocomposites. X-ray diffractometry (XRD) was used to investigate the intercalation effect, crystallite size, and crystal cell parameter in these composites. Two kinds of maleated PP, with graft efficiencies of 0.6 and 0.9 wt %, and two sorts of manufacturing processes were used to prepare nanocomposites and then to investigate their effects on intercalation behavior. The results showed that the intercalation effect was enhanced by increasing the content of PP-g-MAH, using maleated PP with higher graft efficiency, and adopting the mold process. The crystallite size of nanocomposites perpendicular to the crystalline plane, such as (040), (130), (111), and (041), reached the minimum value when the content of PP-g-MAH was 20 wt %. This result indicated that the crystallite size of PP in nanocomposites decreased by proper addition of PP-gMAH. Maximum values in tensile strength (40.2 MPa) and impact strength (24.3 J/m) were achieved when the content of PP-g-MAH was 10 and 20%, respectively. (C) 2003 Wiley Periodicals, Inc.