Effect of aging on dielectric behavior of outdoor polymeric insulators

This paper demonstrates the use of a dielectric spectroscopy technique for monitoring the effect of different ageing: ultra violet radiation (UV), thermal, water immersion, humidity and water boiling on silicone rubber, ethylene-propylene diene monomer (EPDM) and alloy of SIR-EPDM (50/50 wt%). The measurement of dielectric constants and dielectric losses in frequency domain help to quantify the chemical and physical changes in the bulk of polymer due to aging. Samples were subjected to UV light for 1000 h, immersed in water for 1200 h, treated in boiling water for 100 h, heated for 600 h at 100°C and were exposed to 90-95% humidity for 1000 h. Low values of dissipation factor (tan δ) for EPDM reflect its non-polar and loss free nature. EPDM and alloy of SIR-EPDM show low dissipation factor after hydro-thermal aging. In the other hand, silicone rubber show lower tan δ after UV and thermal stress compared to EPDM and alloy of them. Results of this study show the effect of ageing parameters on a material and the comparability of materials with dielectric response measurements in the frequency region (10³ to 10^-2) Hz.