Development of Polymer/Inorganic Nanocomposites Processing Based on an in situ Non-Aqueous Sol-Gel Technology

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Polymer composites containing nanoscale particles have been shown to exhibit properties which differ from and are even superior to those of microparticle blends. In contrast, the formation of blends is hampered by high viscosities and difficulty in achieving a homogeneous particle distribution without agglomeration. In this project application, we propose a new route for preparing polymer nanocomposites based on in situ formation of silica nanosized particles in the polymer matrix during processing. Non-volatile, hydrophobic hyperbranched polyalkoxysiloxanes are employed as silica precursors. The polymeric precursors are tailored for optimum compatibility and processing of polypropylene. Control of the transformation of the polyethoxysiloxane to SiO2-x(OH)2x can efficiently reduce the viscosity of the polymer melt during processing and achieve particle concentrations of more than 10 wt.-% with particle sizes smaller than 50 nm. Whereas pure polyethoxysiloxanes yield spherical silica particles, the in situ creation of layered silicates will be attempted by adding magnesium or aluminium and potassium or ammonium salts, and by using long alkyl-modified polyethoxysiloxanes. The non-aqueous solgel technology developed in this work will be transferred to a continuous process using a corotating intermeshing twin-screw extruder. The resulting nanocomposites will be further processed by injection moulding. Furthermore, the morphology and component properties as well as a complete process analysis will be studied by focussing on nucleation, stiffness and improved impact strength.