In this study, the electrostatic capacity and dielectric loss tangent for 20 μm thick thermal conductivity silicone rubber which is heated at 80 degrees for 8 hours has been measured at temperature of 30℃∼170℃, frequency of 0.1∼1 MHz. The results of degradation evaluation by this study are as follows. In low frequency, it found that the electrostatic capacity decreased with increasing temperature. On the other hand, it confirmed that the range of the electrostatic capacity narrowed with increasing frequency. It confirmed that there are the carboxylic acid structure and C-O bonding at range of wave number 1,000cm-1 to 1,300cm-1.

In this study, the moisture content, charge?discharge current, electrostatic capacity and dielectric loss tangent are measured for the specimen of bisphenol type epoxy resin which is mixed with squared amorphous silica filler and dipped in hot water of 50℃ for 169 days. The results of this study are listed below. The longer of deposition day, the charge and discharge current was increased. It is considered that the reason is because there was water attack through the squared silica surface. The longer of deposition day, the absorption rate of all specimens was increased. It found that the absorption rate reached saturated state after 100 days. The higher frequency and the longer of deposition day, the tanδ was decreased. Also, It found that the tanδ and electrostatic capacity of the specimen which is mixed with squared filler are greater.