Effects of water salinity, electric stress and temperature on the AC and DC flashover voltages of polytetraflouroethylene

The effects of aging of polytertraflouroethylene (PTFE) by immersion in a saline solution at different temperatures and for different durations on the AC and DC flashover voltages in air at 1.01/spl times/10/sup 5/ Pa and 21.5/spl plusmn/3/spl deg/C are reported. The PTFE specimens were immersed in 10 mS/cm saline solutions, of water and were kept at 0/spl plusmn/1.5/spl deg/C, 21.5/spl plusmn/3/spl deg/C, 44/spl plusmn/1.5/spl deg/C and 98/spl plusmn/2/spl deg/C for duration of up to 125 days. The AC (60 Hz) and DC flashover voltages were measured after 10, 23, 45, 100 and 125 days of immersion. The flashover voltage was found to decrease with increasing immersion time and increasing temperature of the solution. The contact angle, the average surface roughness and the change in the weight of specimens due to the uptake of water were also measured and correlated with the AC and DC flashover voltages.