Long-term AC Electrical Treeing Behaviors of Epoxy/Layered Silicate Nanocomposites Prepared by a 3-Roll Mill

Studies on the effects of layered silicate content on the AC electrical treeing and breakdown behaviors of epoxy/layered silicate nanocomposites were carried out in needle-plate electrode geometry. Wide-angle X-ray diffraction(WAXD) analysis and transmission electron microscopy (TEM) observation showed that 1 wt% of the multilayeredsilicate was fully exfoliated into nano-sized monolayers in the epoxy matrix however, over 3 wt% of the silicate was inan intercalated state. When 1 wt% layered silicates were incorporated, an electrical tree was initiated in 439 min andpropagated at a speed of 2.3 μm/min after applying 781.4 kV/mm, representing a decreased in starting initiation timeby a factor of 11.0 and increase in propagation speed by a factor 8.2 in comparison with neat epoxy resin. These valueswere in great decline after the layered silicate content was increased to 3wt% which implies that the exfoliated silicateblocked the tree initiation and propagation processes effectively. However the effect was largely decreased in theintercalated state.