期刊
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
卷 18, 期 6, 页码 1955-1962出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TDEI.2011.6118633
关键词
polyimide; electrical breakdown; dielectric strength; Weibull distribution; thermal exposure; immersion in water
资金
- NASA [NNX07AU54A]
Polyimide (PI) tape has been widely used as electrical insulation for wires and cables due to its excellent balance of electrical, mechanical and thermal properties. However, insulation materials are exposed to various environmental degradation mechanisms during service, which can cause deterioration of their insulation properties. In this paper, the effects of thermal exposure and immersion in water on dielectric strength of Kapton (R) HN PI film are investigated statistically by two-parameter Weibull distribution analysis. The PI samples were heated at 475 degrees C for 1 to 4 h, and at 450 to 480 degrees C for 4 h, to study the influence of thermal exposure. Moreover, to explore the effect of moisture absorption, other PI samples were immersed in distilled water for up to 96 h at room temperature. After the degrading process, breakdown voltage and thickness were measured at 20 different points on each sample. The Weibull cumulative distribution function for each of the degraded samples was plotted, and compared with that of a sample dried by heating at 200 degrees-C for 1 h. Significant decreases in both the scale parameter and the shape parameter of the Weibull distribution, obtained through least-squares regression, are observed, indicating a statistical decrease in dielectric strength and a more dense dispersion of electrical weak points in PI. This observed deterioration of insulation capability of PI is attributed to chemical degradation and formation of ionic side groups during heating and immersion in water, respectively.
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