Polyethylene maleic anhydride grafted polyethylene organic-montmorillonite nanocomposites. I. Preparation, microstructure, and mechanical properties

In this study, three cationic surfactants (hexadecyltrimethylammonium chloride, hexadecyldimethylbenzylammonium chloride, and octadecyltrimethylammonium chloride) were used to modify montmorillonite and polyethylene (PE)/maleic anhydride grafted polyethylene (PE-g-MAH)/organic-montmorillonite (Org-MMT) nano-composites, prepared by two blending processes (direct-melt blending and solution blending). X-ray diffractometry and transmission electron microscopy were used to investigate the intercalation behavior and microstructure of composites. Mechanical properties were also tested. It was found that the intercalation effect of PE/PE-g-MAH/Org-MMT could be enhanced by increasing the content of PE-g-MMT, using the silicate modified by a cationic surfactant with a benzyl group or long alkyl chain, adopting the solution-blending method or using high-density polyethylene as matrix. The degree of crystallinity of composites and the crystalline thickness perpendicular to the crystalline plane [like (110) and (200)] decreased with increasing amounts of PE-g-MAH and, under certain prescription, the crystalline thickness of the composite made by the solution method was much smaller than that made by direct-melt blending. This clearly showed that Org-MMT and PE-g-MAH had a heterogeneous nucleation effect on crystallization of PE from the melt, resulting in a decrease of crystalline thickness, and the heterogeneous nucleation effect was more evident in the nanocomposite made by the solution-blending method than in that made by the direct-melt intercalation process. The tensile strength initially increased and then decreased with increasing contents of PE-g-MAH. The maximum value in tensile strength (23.3 MPa) was achieved when the concentration of PE-g-MAH was 6 wt %. The impact strength increased concomitantly with the content of PE-g-MAH; it was 122.2 J/m when the concentration of PE-g-MAH was 9 wt %. (C) 2004 Wiley Periodicals, Inc.