Effect of silica particles on electrical treeing initiation in silicone rubber

Silicone rubber (SIR) widely used in the insulation of the prefabricated power cable accessories is actually a kind of polymer composite which is usually composited by neat SIR and several weight percentages of silica (SiO₂) particles. The aim of dispersing SiO₂ powders into the SIR is mainly to enhance the mechanic properties of the polymer. Some research indicates that the particles may also affect the electrical treeing progress of the polymer composite. Electrical treeing is one of the main causes of degradation and breakdown of solid insulating material such as SIR. In this article, a serial of SIR samples with different weight percentages of SiO₂ particles were made, a classic needle-plate electrode system was used to test their electrical treeing initiation performance and an optical microscope system was founded to observe the electrical treeing progress. In the experiment, the AC voltage applied on the electrodes was raised at a certain rate and when the electrical trees initiated in the SIR samples, the voltages and the photos of the trees were recorded. By comparing the results of experiment, it was found that when the weight percentages were under a threshold value, the SiO₂ particles hindered the electrical tree growth in the polymer composites. This work afforded experimental evidence to the research on the electrical treeing in polymers.