The heat treatment effect on the EPDM's electrical performances
Résumé
This paper presents a thermo-electric experimental study of treeing structures expanding in EPDM (Ethylene Propylene Diene Monomer) in a point – plane electrode geometry. Accelerated electrical degradation tests, under alternating 50 Hz electrical field, were carried out for two states of this material namely for untreated and heat-treated EPDM. The tests are performed at different temperatures, for a limited processing time. First, it comes to measure the tree length, the partial discharges (PDs), the threshold voltage (Us), the dissipation factor (tgδ) and the capacitor (Cx) of insulation, accompanying the evolution of tree structures. Then chemical analysis by Scanning Electron Microscopy (SEM), Infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD) are undertaken to identify the changes in the morphology and microstructure of damaged thermally treated and untreated polymer. The obtained results evidence the fact that the heat treatment improves the material performances by delaying the tree progression and improving thereby the associated electrical characteristics.