Synthesis of Silica/Polyolefin Nanocomposites via Two-step Method

In situ polymerization of ethylene was used to prepare silica/PE parent material (46.8 wt% of SiO2), which was then blended with PE (and PP) to synthesize silica/polyolefin nanocomposites (a two-step method), such as PE05, PE10, and PE20 (or PP05, PP10, and PP20), whose silica contents were 0.5 wt%, 1.0 wt%, and 2.0 wt%. For comparison, silica/polyolefin nanocomposites with 2.0 wt% of SiO2 were also prepared via blending method (PE20M and PP20M). TEM, TGA and tensile test characterization results showed that the nanocomposite prepared via the two-step method behaved better than that prepared via blending method, as for nanosilica dispersion, thermal stability, crystallinity, and tensile mechanical properties. For example, the dispersion of nanosilica particles in PE20 was better than that in PE20M. The temperatures of maximum weight loss rate (Tp), crystallinity and strength of PE20 were 472ºC, 68.3% and 28.3 MPa that were improved compared with those of PE20M, which were 430ºC, 66.3% and 26.3 MPa, respectively. Furthermore, the two-step method could utilize minimum amount of in situ polymerization product to produce maximum amount of nanocomposite. All these findings have shown that the two-step method can easily and cheaply produce silica/polyolefin nanocomposites with high quality.