| 摘要 |
1,135,998. Polycarbonate electrets. NORTHERN ELECTRIC CO. Ltd. 20 Oct., 1967 [1 Nov., 1966], No. 47861/67. Heading C3R. [Also in Division H1] An electret comprises a polycyclic bisphenol polycarbonate which has a high volume resistivity and which has been permanently electrostatically polarized. Preferably the polymer chain has attached to it a norbornane ring which may be fixed to another ring. A film of the polymer, sandwiched between a pair of insulating plates, is placed between two electrodes and a potential applied at 120‹ C. for half an hour. While maintaining the field, the temperature is allowed to fall to room temperature, then the electrodes are removed.
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