Preparation of epoxy/micro- and nano- composites by electric field dispersion process and its mechanical and electrical properties

In order to develop a new insulation material for heavy electric equipments, epoxy/micro- and nano- composites (EMNC) were prepared by mixing a micro-sized silica with a nano-sized layered silicate, where the latter had been pre-prepared by our electric field dispersion process in the following ac electric field condition; (1) interelectrode distance: 40 mm, (2) application voltage: 11 kV, (3) frequency: 1 kHz, and (4) application time: 30 min. To characterize the epoxy/layered silicate nanocomposite, WAXS and TEM analyses were carried out. The weight ratios of epoxy matrix : microsilica: nano-sized layered silicate were 39.7: 60: 0.3 and 34.7: 65: 0.3, and ac electrical insulation breakdown strength, dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), tensile and flexural strength were measured. WAXS and TEM analyses were verified that the multilayered silicate was exfoliated to nano-sized monolayer silicates and they were evenly dispersed among the micro-silica particles. As micro-silica content increased, tensile and flexural strength increased, while the ac electrical insulation breakdown strength decreased. However, all these properties became higher by extra-addition of 0.3 wt% exfoliated layered silicates.