Impact of Dispersion Processes and Surfactant on Performance of Silica-Silicone Nanocomposites

In this study, various silicone nanocomposites are studied to investigate the effects of filler treatments, such as calcination, use of surfactant, and mixing methods on filler dispersion and distribution. A two-part room temperature vulcanized silicone rubber is used as a base polymer and reinforcing nanofumed silica as a filler. A fixed filler concentration of 10 wt% has been selected for the comparative studies. The electrostatic disperser (ED) that is effective in mixing nanofillers is used to prepare the composites, with or without polyalkyleneoxide modified heptamethyltrisiloxane, the surfactant. Comparisons are also made with some samples prepared using the conventional high shear (HS) mixer. Fillers were used as obtained and/or after calcination at 500 °C. The performances of prepared nanocomposites are evaluated by comparing their thermal, mechanical, morphological, and dielectric properties. The thermogravimetric analysis (TGA) and mechanical properties, tensile strength and elongation at break, show that nanocomposites prepared using ED with calcined filler in the absence of surfactant have the highest thermal stability and tensile strength. Dielectric analyses, both at room temperature and elevated temperatures of 50 °C, 75 °C, and 100 °C, further show that those composites with calcined fillers in the absence of surfactant have lower relative permittivity and loss factor than those with surfactant. The observed differences in thermal, mechanical, and dielectric properties are related to the way fillers bond with the polymer matrix and additional interfaces created by the surfactant. The morphological analysis supports the empirical correlations derived.