Intrinsic Self-healing Characteristics of Electrical Tree in Silicone Rubber

The self-healing phenomenon of electrical tree in traditional silicone rubber (SiR) insulation material, which is called intrinsic self-healing, is demonstrated and investigated in this paper. For initial SiR samples with electrical trees, with the removal of applied voltage, it is found that some electrical tree branches naturally disappear in the visual field with time. A less branched morphology and decreasing fractal dimension of electrical tree are thus observed. The effects of temperature on the intrinsic self-healing characteristics are explored and the intrinsic self-healing process can be considered as taking place in three stages based on the temperature-dependent self-healing rate. It is proposed that the intrinsic self-healing behaviors are closely related to the gas motion in the tree channels and the retractive force of SiR, which is affected by the conformation of molecular chains. Re-growth performance of electrical tree is conducted on the self-healed samples and many tiny branches at the sidewall of main channels are found in the repeated electrical trees, while the tree length remains unchanged. Furthermore, some electrical trees vanish in self-healing regions after the re-growth process, which can be attributed to the shielding effect of dense branches and the reconstruction of some hydrogen bonds between nano-silica and molecular chains of SiR.