In this study, we investigated the influence of the surface treatment of Al nanoparticles on the electrical properties of linear low density polyethylene composites. Octyl-trimethoxysilane was used as a nonpolar silane coupling agent for the surface treatment of Al nanoparticles. It was found that the incorporation of nonpolar octyl groups onto the surface of Al nanoparticles not only increased the percolation threshold and the resistivity but also improved the dielectric properties as compared to the composites filled with unsurface-treated nanoparticles. The surface treatment makes it possible to easily control the frequency and concentration dependences of dielectric constant and provided an excellent approach able to considerably reduce the dielectric loss of the nanocomposites, which is of great significance from the viewpoint of practical application of the polymer/metal nanocomposites in the electrical and electronic industries. It is concluded that the improved electrical properties could be directly ascribed to the good dispersion and special electrical feature of the surface-treated nanoparticles in the polymer matrix.

Nano-silica particles were employed for enhancement of epoxy vacuum pressure impregnating (V.P.I.) resin. The influences of nano-silica particles on the curing reaction, glass transition temperatures, dielectric behavior, and thermomechanical performances were investigated. The activation energy (E) for the epoxy curing reaction was calculated according to Kissinger, Ozawa, and Friedman-Reich-Lev methods. The glass transition temperatures were determined by means of differential scanning calorimetry, dynamic mechanical analysis, dc conduction, and ac dielectric loss analysis. Relationships between the glass transformation behaviors, the thermomechanical performances, and the dielectric behaviors were discussed. The influences of nano-silica particles on the mechanical properties were also discussed in terms of non-notched charpy impact strength and flexural strength. The morphologies were studied by means of SEM and TEM. The results indicated that nano-silica particles could effectively increase both the toughness and strength of epoxy resin at low loadings (no more than 3 wt %) when nano-silica particles could be well dispersed in epoxy matrix without any great aggregations.

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