Optimizing melt-processing conditions for the preparation of iPP/fumed silica nanocomposites: Morphology, mechanical and gas permeability properties

A series of iPP/SiO2 nanocomposites, containing 1, 2.5, 5, 7.5, and 10 wt.-% fumed silica nanoparticles, were prepared by melt mixing in a twin screw co-rotating extruder. The effect of different extrusion parameters was evaluated. The size of aggregates increased with increase inSiO(2) content and repetition of the mixing process improved the filler's dispersion. A similar effect was also exhibited by either increasing the rotor speed or the mixing temperature, with the latter being more pronounced at the ranges studied. The mechanical properties of the prepared nanocomposites were evaluated and various models used to explain the observed enhancements. However, only the three-phase model could provide some correlation with the experimental results. All nanocomposites displayed lower permeability to gases.