Electrokinetic modelling of dielectric endurance

An electrokinetic model of breakdown in polymers aims to explain the kind of breakdown process that occurs over a relatively long timescale in high-quality (uncontaminated, defect-free) materials, in contrast to the quick and violent modes of breakdown that are often experienced, when materials are overstressed. Undoubtedly, we require a multi-stage model, which will vary somewhat, depending on the exact composition of the material and its environment. 

consider the mechanical stresses developed in a material as an electric field E is applied to it. The material will deform until the Maxwell electric stresses are balanced by changes in the mechanical stresses. For an 

2 The mechanical effects of an electric field on a material are usually expressed by means of the electrostriction tensor defined by  

In polyethylene the ac-relaxation process (see Section 3.4) enables the movement of chains into and out of the crystalline lamellae. Theoretical treatments have demonstrated that it most probably proceeds by propagation of a localized twist (180° rotation) about the chain axis extending over 12 CH2 units (Fig. 6.14). As the twist defect travels along the chain, it rotates and translates the chain by half a unit cell (i.e, by one CH2 unit) - this is termed the c-shear process (Mansfield and Boyd, 1978). The activation energy for this process is about HOkJmoF1, corresponding to the extra energy required to introduce the twist defect into the crystal. Once formed, the twist can freely 

The ground state of an oxygen molecule is unusual in that it is a triplet state, i.e. in effect, it is a diradical  

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