Effects Of Gamma-ray Irradiation On Dielectric Breakdown Of Insulation Polymers

In space and nuclear power stations,polymer insulating materials are inevitably exposed to various kinds of rays (such asα-ray,β-ray,γ-ray and so on) . The rays can change the structures of the polymers, and then change their electrical performance. Accordingly, it becomes necessary to investigate the effects of the radiation on insulation materials. In practice, many environments factors are co-existing, for example, temperature and vacuum in space environment. So it is necessary to consider other factors when discussing the effects of the radiation. However, knowledge of influence of irradiation under combined conditions is limited, and systematic study is desirable. With the coming of the nuclear-day and development of the space fighting technology, more and more electric and electronic devices are used in various irradiation environments and the polymers must satisfy the demand. Therefore, from the view of safety, it's very important for us to investigate the dielectric property of the polymers under the combined irradiation environments.This paper describes the effects of gamma-ray irradiation and reduced pressure on dielectric breakdown of polybutylene naphthalate (PBN) and polybutylene terephthalate (PBT) by applying a dc pulse voltage. Both PBN and PBT were irradiated in air up to 100 kGy and then up to 1000 kGy with a dosage rate of 10 kGy/h by using a 60Co gamma-source. The total dose and reduced pressure's effects on time to dielectric breakdown and discharge quantity were discussed. Obtained results show that with increasing the total dose, the discharge quantity decreased with PBN, but increased with PBT. With decreasing the atmospheric pressure, the discharge quantity increased with PBN, but decreased with PBT. With increasing the total dose, the time to dielectric breakdown increased with PBN, but decreased with PBT. With decreasing the atmospheric pressure, the time to dielectric breakdown increased with both PBN and PBT. The experimental results suggest that the chemical structure of polybutylene polymers play a main role in the result of radiation reaction, which is related to cross-linking and degradation reaction.