Dynamic Mechanical Properties of Polymer Dispersed–Silica Nanoparticle Composites

A series of nanocomposites were prepared by dispersing various silica nanoparticles in polystyrene (PS) and poly(methyl methacrylate) (PMMA) and analyzed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Colloidally dispersed silica nanoparticles and structured fumed silica were used in the synthesis, leading to well-dispersed systems. A detailed investigation was conducted into the thermal and dynamic mechanical behavior of the nanocomposites. The findings of this study demonstrate that the incorporation of filler particles increases the glass transition temperature (Tg) and suppresses polymer flow, resulting in an extended rubbery plateau. Significant reinforcement as evidenced by an increased plateau modulus above Tg was only observed for samples containing fumed silica. While neat PMMA begins to flow and deform irreversibly above 150 °C, the fumed silica/–polymer hybrid materials remain stable up to 240 °C, exceeding the polymer’s Tg by over 100 °C. The polymer nanocomposites exhibited slight mechanical damping at high temperature as evidenced by a surprisingly low tan δ (<0.1). Compared to the structured fumed silica hybrids, colloidally dispersed silica had very slight effect on polymer reinforcement.