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

Abstract

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.