ポリn-アルキルメタクリル酸エステルをポリマー成分とするカーボンブラック・ポリマー複合体の電気的性質

抄録

In this paper, the effect of the glass transition temperature (T_g) on the electrical properties of carbon black-polymer composite resistors has been investigated. The resistors were made by mixing the furnace black with poly-methylmethacrylate (PMMA) or Poly-laurylmethacrylate (PLMA) and coating the mixture on porcelain plates. The resistance was measured in the heat cycle between 40 and 140°C.
For the resistors containing PMMA with higher T_g than 80°C, the resistance increased rapidly at about T_g on the first heating half cycle and became unchanged at 40°C after the subsequent cooling half cycle. On the second temperature cycle, the resistance change was comparably small and the resistance change at 140°C was about 17% at the most, while the reproducibility on the temperature cycle was better. From the dilatometric measurement, it was found that T_g of PMMA mixed with carbon black shifted to a higher temperature and became obscure. This change in T_g was considered to be a reason why the resistance change became smaller on the second heating cycle.
The composite resistor containing PLMA with T_g of -65°C shows no anomaly against the temperature cycle between 40 and 140°C. It was shown that the specific volume of the composition changed irreversibly against the temperature cycles. From this result, it is estimated that the rearrangement of carbon black network in the polymer matrix may occur.
However, the resistors obtained from the copolymer of laurylmethacrylate with glycygylmethacrylate, which can be crosslinked with ethylene diamine, showed an anomaly even in the absence of T_g, when resistors were cured with ethylene diamine.