Dielectric breakdown in polyethylene at elevated temperatures

Fig. 2 shows the results obtained for the A.C. (60 Hz) breakdown strength LDPE as a function of temperature from 51 to 150°C. The dielectric strength decreases monotonically with increasing temperature up to the melting temperature (110°C). Above 110°C, the breakdown strength is only weakly dependent on temperature, decreasing slightly with increasing temperature. The error bars shown are a measure of the standard deviation of each set of measurements. It is noteworthy that a marked decrease in standard deviation occurs as the polymer becomes more viscous at elevated temperatures.