Effect of morphology, proton irradiation and pre-stressing on the breakdown of LDPE

It is a well-known fact that the breakdown of low density polyethylene depends on the space charge accumulation in the polymer bulk. In turn, the process of a space charge accumulation is governed by a sub-microscopic structure of polymers, the contact conditions on the interface electrode/polymer and the charge carriers injection from electrodes. It is shown that the surface modification of the LDPE samples by proton irradiation allows the number of impulses to breakdown to be increased. One more way to increase the life time and the breakdown strength of LDPE is the so-called pre-stressing, i.e., preliminary polarization of LDPE under dc voltage. A larger increase in the number of impulses to breakdown is observed in the LDPE samples after simultaneous application of dc pre-stressing and modification of the LDPE surface layers by proton irradiation. This phenomenon is related to the homo-charge accumulation near the electrodes.