Effective surface functionalization of fumed silica with NBR telechelic oligomer for high-voltage polyolefin-based dielectric composites

In this study an effective surface functionalization of fumed nano-silica for dielectric insulation composites is developed. A three step modification procedure was applied: 1. Silanization of the silica surface with (3-glycidoxypropyl)trimethoxysilane (GOPTMS); 2. Grafting of an acrylonitrile-butadiene telechelic oligomer terminated with two carboxylic acid groups (o-NBR); 3. Hydrogenation of the unsaturated polybutadiene segments for better compatibilization with the saturated polyolefin matrices and for higher dielectric performance.The deposition of the coupling system was monitored by thermogravimetric analysis (TGA) revealing 6.4 wt. % of GOPTMS and 13.6 wt. % of o-NBR bond to the silica, resulting in an exceptionally high total deposition (20.0 wt. %). The o-NBR grafting was analyzed qualitatively by Fourier transform infrared spectroscopy (FTIR) showing successful deposition of o-NBR and effective hydrogenation.The silica modified according to this procedure is a promising functional nano-filler for high-voltage insulation composites allowing improved dispersion and distribution in polyolefine matrices and therefore enhancing their electrical properties.