Homogeneously Dispersed Poly(propylene)/SiO 2 Nanocomposites with Unprecedented Transparency

Summary: Physico‐chemical interactions between hydrophobic polyolefin materials and hydrophilic inorganic nanoparticles such as surface‐hydroxylated SiO 2 have not been well understood so far. In this study, the effects of particle size and content of SiO 2 nanoparticles on isothermal growth rate of PP spherulites in various PP/SiO 2 nanocomposites were investigated by polarized optical microscopy. It was unexpected to find that hydrophilic SiO 2 nanoparticles can be homogeneously dispersed in a PP matrix. Spherulite growth rates of PP in PP/SiO 2 nanocomposites decrease significantly with increasing SiO 2 content and decreasing particle size. Most interestingly, the spherulite growth rate was zero for PP/16 nm‐SiO 2 nanocomposites with SiO 2 content above 2.5 wt.‐% resulting in a highly transparent film.Photographs of 200 µm‐thick PP and PP/16 nm‐SiO 2 (5 wt.‐%) sheets in front of a graphic pattern.