スチレン基の導入がポリエチレンの誘電・絶縁特性に与える影響

抄録

Recently, as quantum chemical methods such as DFT method have widely investigated on the dielectric and insulating materials, electronic and orbital structures of the materials which contain aromatic groups in the molecular chain have been gradually becoming apparent. From the quantum chemical view points, the styrene group has higher HOMO and lower LUMO levels compared to those of polyethylene, and this means the styrene groups may form a new molecular orbital between the HOMO/LUMO levels of polyethylene as a trap site of electric charges. The influences of styrene groups on the molecule of polyethylene were investigated in 30 years ago as the ethylene-styrene random copolymer manufactured by high pressure method. The content of styrene in the copolymer was said to be less than 1 wt % which gave a most appropriate dielectric and insulating properties, but their properties which relate to molecular orbital such as space charge behavior were less studied then. We have obtained some of commercially available styrene modified polyethylene, and investigated the influences of styrene groups on dielectric and insulating properties theoretically and experimentally. As the results, even more contents of styrene than that of previous studies show a more excellent dielectric and insulating properties than polyethylene.