Enhancement of tracking resistance of silicone rubber through charge dissipation and radical capture by fluorosilane-grafted iron oxide

Fluorosilane-grafted iron oxide (F-Fe2O3) was prepared via surface grafting reaction between iron oxide and perfluorooctyltriethoxysilane. The effect of F-Fe2O3 on the tracking resistance (TR) of addition-cured liquid silicone rubber (ALSR) was investigated by the inclined-plane test (IPT), surface potential decay test (SPDT), thermogravimetry (TGA), corona aging test and scanning electron microscopy (SEM). F-Fe2O3 delayed the occurrence of the intensive arc discharge and reduced the number of arc discharges. The corona resistance and TR of ALSR were effectively improved. ALSR/F-Fe2O3 with 0.15 phr F-Fe2O3 content passed the IPT at 4.5 kV, showing an erosion mass of 3.17%. The hydrophobicity and thermal stability of ALSR were also enhanced. The SPDT showed that F-Fe2O3 effectively dissipated charge. The results of thermal stability and corona resistance tests revealed that F-Fe2O3 could capture free radicals generated by the oxidation of methyl side groups of ALSR chains and thus inhibit the thermal degradation of ALSR during the arc discharge. Moreover, the charge dissipation by F-Fe2O3 could diminish the accumulation of charges in ALSR and reduce the damage of charges to the chains during arc discharge. Therefore, the TR of ALSR was enhanced.