The significance of electroluminescence in polyolefins

Electroluminescence has been widely reported in large band gap insulating polymers under any kind of electrical stress, being ac, dc, impulse etc. but its significance is still the matter of debate. It was first investigated in the late seventies in divergent field experiments (i.e. using needle electrodes embedded in the material) as a precursor of electrical treeing. Later on in the nineties, uniform field experiments (i.e. using semi-transparent or transparent electrodes on top of a polymer film) were carried out. The main advantage of the divergent field configuration is the possibility to focus physical/chemical microanalysis in the tiny high field region around the needle tip for characterizing material degradation, which is not easy under uniform field owing to the low level of deterioration and its likely local character. The main advantage of the uniform field configuration is the possibility to correlate electroluminescence with real-time space charge distribution measurements as well as to acquire wavelength-resolved emission spectra. In this communication, we discuss the consistency of the experimental results obtained in divergent/uniform field experiments and the cross-fertilization between the two as regards the relationship between electroluminescence and material degradation.