Izumi Ishikawa

The effect on dielectric loss of polyethylene caused by acetophenone and cumylalcohol

The effects of acetophenone (AP) and cumylalcohol (CA) on the tan/spl delta/ of low density polyethylene (LDPE) were investigated in detail taking the temperature range of 25 to 100/spl deg/C and electrical stress range of 5 to 40 kV/mm. The tan/spl delta/ of LDPEs to which AP and CA (reagent special grade) and these additives purified by absorbent (activated clay) have been added, was compared with the tan/spl delta/ of LDPE without any additives. The analysis by dividing tan/spl delta/ into the dipole factor tan/spl delta//sub D/ and the conductive factor tan/spl delta//sub c/ (tan/spl delta/-tan/spl delta//sub D/+tan/spl delta//sub C/) showed that the additives (AP, CA) have only very small influence on tan/spl delta//sub D/ above room temperature. On the other hand, since the contribution of tan/spl delta//sub C/ markedly increases in the higher temperature and higher electrical stress region depending so much on whether additives are added or not and whether the additives are purified or not, ionic carriers were estimated as carriers of tan/spl delta//sub C/. Two kinds of carrier source, that is to say, the carriers with small activation energy (/spl sim/9 kcal/mol) and the carriers with large activation energy (/spl sim/18 kcal/mol) were estimated in the tan/spl delta//sub C/ of LDPE with additives. The former carriers (with small activation energy) could be removed by purification of additives, resulting in large reduction of tan/spl delta//sub C/ in the high electrical stress region. However, even after the purification, the latter carriers (with large activation energy) could not be removed sufficiently, showing 2 to 3 times of the carrier concentration as much as LDPE without additives.<<ETX>>