Comparative study of AC breakdown voltage for various polymers: Influence of electrodes shape, thermal and hydrothermal ageing

This work deals with a comparative study of AC breakdown voltage (BDV) of various polymeric samples. The investigated materials cover thermoplastics (namely polyamide 6 (PA6/50), fireproofed polyamide 66 (PA66/50), polyarylamide (PARA/50), polycarbonate (PC/40), polyethylene (HDPE) and polyphenylene sulfide (PPS/65)); and two EPDM based elastomers (namely unfilled EPDM (EPDM) and fireproofed EPDM (EPDM V0)). We mainly analyze: (i) the effect of electrodes shape (namely cylindrical and spherical); (ii) thermal ageing at high temperatures (100, 130 and 150°C); and (iii) hydrothermal ageing in salt fog conditions. It is shown that obtained BDV with spherical electrodes exhibits the highest values because of small surface contact of electrodes with polymeric surfaces; materials such as PEHD and EPDM show the highest BDV. It is found that thermal ageing affects seriously BDV of EPDM based materials. PPS/65 depicts the lowest BDV but is less affected by thermal ageing because of its high thermal stability. Hydrothermal ageing reveals that the moisture absorption is the main reason of the significant decrease of BDV for polyamides.