Effect of different amine modified clays on the compatibility and clay dispersion of polypropylene nanocomposites

Abstract

The compatibilization effects provided by different amines in the synthesis of polypropylene/amine modified montmorillonite clay nanocomposites (PP/ A-MMT) were studied. Nanocomposites were prepared by melt processing using a twin-screw extruder, by compounding maleic anhydride grafted polypropylene (PPgMA) with MMT modified with three different amines: ethanolamine (EA), hexamethylenediamine (DA6) and 1,12-diaminododecane (DA12) to form amine modified montmorillonite ``A-MMT{''}. FTIR characterization confirmed the formation of characteristic amide linkages and X-ray confirmed the intercalation of PPgMA between the silicate layers. X-ray, scanning electron microscopy with transmission modulus (STEM), thermogravimetric analysis (TGA), rheological properties plus mechanical properties were used to characterize those nanocomposites. X-ray diffraction patterns of the composites using A-MMT showed 001 basal spacing enlargement with good clay exfoliation-intercalation compared with the natural MMT (Na-MMT). The DA12 modified MMT showed the greatest increase in basal spacing. TGA revealed that the decomposition of the composite took place at a slightly higher temperature than that of neat PP. Nanocomposites using EA or DA6 modified MMT showed a decrease in viscosity whereas those using DA12 showed an increase in viscosity. Nanocomposites using the DA12 modified MMT showed the most substantial improvement in terms of both mechanical properties and clay exfoliation. It appears that the longer the amine chain the higher the separation of the clay platelets and the higher the interactions between the clay and the polymer matrix.