Silica surface modification with liquid rubbers & functional groups for new polyolefin-based dielectric nano-composites

A novel hybrid approach for surface modification of nano-silica for polyolefin-based dielectric composites is presented. A fumed nano-silica was modified with long oligomeric chains of a liquid rubber, connected via urethane bonds to the silica surface increasing the compatibility with the matrix. Additionally, a secondary amino-silane was grafted in order to alter the charge trapping properties of the silica. The long oligomeric chains provide good dispersibility of the nanosilica in polypropylene/poly(ethylene-co-octene) (PP/POE) blends, while the functional urethane group along with a secondary amino-silane affected the charge trapping properties of the nano-composites by reducing the charge traps density and simultaneously increasing their depth. Scanning Electron Microscopy along with Differential Scanning Calorimetry revealed that the silica is preferably located in the PP phase, most likely due to its lower viscosity in comparison to POE. The silica particles exhibit a nucleating effect visible in a noticeable increase of the crystallization temperature of the PP phase, especially when the silica surface treatment is performed.