Effect of water salinity and temperature on the hydrophobicity of ethylene propylene diene monomer insulator

Ethylene propylene diene monomer (EPDM) is extensively used in outdoor composite polymer insulators. The effects of water salinity and temperature on the hydrophobicity of EPDM rubber were studied The hydrophobicity was determined by measuring the contact angle using a droplet of distilled water. The specimens were immersed in saline water solutions for up to 576 h. The salinity levels used were 5, 10³ , 10⁴ and 10⁵ μS/cm. The aging temperatures were 0, 25, 50, 75 and 98°C. The weight was also measured to determine the amount of water absorption in the polymer as might occur during a heavy rain. The change in the contact angle is related to the amount of water absorption, the salinity level of solution and the temperature. The absorption of saline water into the bulk is larger at higher temperatures and decreases with increasing salinity. At 25°C and higher the absorption of saline water at all salinity levels was saturated during the aging period Generally, after long immersion the contact angle decreased. At 0°C the decrease of contact angle was larger at higher salinity. At high temperatures (⩾75°C), the sample surface gradually changed its color from the original dark gray to white