Study on the Thermo-oxidative aging Properties of Nano-SiO2 Composites Based on Cross-linked Polyethylene

Abstract

Cross-linked polyethylene (XLPE) is widely used as insulating material in the power cables. However, under the influence of heat and oxygen, XLPE is prone to be thermal aged and degraded, which affects the safety of the cable. In this study, pure XLPE and nano-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /XLPE composites were prepared, and aged at $165 ~^{\circ}\text{C}$. The oxidation induction time (OIT) of different samples during thermal aging were obtained by differential scanning calorimeter. The elongation at break and thermal aging lifetime of different samples were obtained through tensile experiments, and the critical OITs of different samples were obtained through thermal aging lifetime. In addition, nano-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /XLPE composites with different concentrations of antioxidants were prepared, and the OIT of the aged samples was measured to characterize the aging process. The experimental results indicate that nano-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> can slow down the consumption of antioxidants, improve the thermal oxidative aging resistance, and prolong the thermal aging lifetime of XLPE. The thermal aging lifetime of XLPE can be increased from 60 h to 79 h at $165~ ^{\circ}\text{C}$. Different concentrations of nano-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> have a similar effect on the thermal oxidative aging process of XLPE. The critical OIT of pure XLPE is about 5%, which increases to about 15% after adding nano-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . Changing the concentration of antioxidant will change the initial OIT of the sample, but will not affect the rate of antioxidant consumption during thermal aging.