Influence of metal inclusions on AC breakdown strength in EPDM

The aim of this work was to investigate the influence of metallic particles on the AC breakdown strength in EPDM rubber. Filled and unfilled EPDM rubbers were contaminated with two different particle sizes (50 /spl mu/m and 165 /spl mu/m) and different particle concentrations, to ascertain their influence on the breakdown strength. The inclusions were irregularly shaped iron particles. The breakdown tests were carried out by using /spl sim/0.7 mm thick circular rubber slabs between cylindrical electrodes. The result yielded the characteristic AC breakdown strengths of 78 kV/mm and 86 kV/mm respectively for non-contaminated filled and unfilled rubbers. The electric strength was considerably lowered for larger inclusions but not in the case of smaller ones. A statistical evaluation of the results is also provided.