Preparation and enhanced properties of poly(propylene)/silica-grafted-hyperbranched polyester nanocomposites

A series of poly(propylene) silica-grafted-hyperbranched polyester nanocomposites by grafting the modified hyperbranched polyester (Boltorn(TM) H2O), possessing theoretically 50% end carboxylic groups and 50% end hydroxyl groups, which endcapped with octadecyl isocyanate (C19), onto the surface Of SiO2 particles (30 nm) through 3-glycidoxy-propyltrimethoxysilane (GPTS) was prepared. The effect of silica-grafted-modified Boltorn(TM) H20 on the mechanical properties of polypropylene (PP) was investigated by tensile and impact tests. The morphological structure of impact fracture surface and thermal behavior of the composites were determined by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The melt viscosity of composites was investigated by melt flow index (MFI). The obtained results showed that: (1) the modified Boltorn(TM) H20 was successfully grafted onto the SiO2 surface confirmed by FT-IR and X-ray photoelectron spectroscopy (XPS) analysis; (2) the incorporation of silica-grafted-modified Boltorn(TM) H20 (3-5 wt% SiO2) greatly enhanced the notched impact strength as well the tensile strength of the composites; (3) the incorporation of silica-grafted-modified Boltorn(TM) H20 had no influence on the melting temperature and crystallinity of PP phase; (4) the MFI of PP composites increased when the silica-grafted-modified Boltorn(TM) H20 particles were added compared with PP/ SiO2 or PP/SiO2-GPTS composites. Copyright (C) 2004 John Wiley Sons, Ltd.