| 摘要 |
PURPOSE:The titled composition exhibiting improved corona resistance, comprising an aromatic polyimide an boron nitride powders. CONSTITUTION:An aromatic tetracarboxylic acid dianhydride (e.g. 3,3',4,4'-bi phenyltetracarboxylic acid dianhydride) and an aromatic diamine (e.g. p-phenylenediamine) are reacted in a molar ratio of 7:3-5:5 in an organic polar solvent (e.g. pyridine) to obtain an aromatic polyamic acid solution having a polymer concentration of 3-35wt% and a logarithmic viscosity number of 0.1 or higher. Then, 1-50pts.wt. boron nitride powders having particle diameters of 1.0mu or smaller are incorporated into 100pts.wt. nonvolatile matter (an aromatic polyimide to be obtained finally) in the polyamic acid solution, to be dispersed homogeneously, which are applied on an article to be insulated, and baked to imidize the polyamic acid.
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