PROJECT TITLE :
Effects of water absorption on surface charge and dielectric breakdown of polyimide/Al2O3 nanocomposite films
The incorporation of inorganic nano particles (TiO2, Al2O3 and SiO2 etc.) with polyimide (PI) greatly improves its dielectric property. The dielectric properties of PI films are largely influenced by the absorbed water and humidity. What is a lot of, the water absorption can be affected greatly by nano particles. In this paper, to study the results of absorbed water on dielectric properties of moistened PI/Al2O3 composite film, PI film specimens were prepared by incorporating twelve wt% nano Al2O3 particles with PI. The first specimens were additionally prepared for distinction. Then the specimens were immersed in high purity water for twelve, twenty four, forty eight, seventy two, 96, a hundred and twenty, fourteen4 and 168 h. The water absorption and breakdown strength underneath totally different immersion time were measured. Meanwhile, given that the existence of surface charge had a crucial influence on the breakdown characteristics, the corona charging tests were conducted at room temperature beneath pulse voltage. The pulse frequency was three hundred, 60zero and 900 Hz, respectively. The pulse amplitude was +four kV. The charge dissipation was investigated based mostly on the demarcation energy theory. Obtained results show that the moisture condition affects more on the nano Al2O3 composite films than the original ones. Compared to original PI films, the water absorption is larger and the breakdown strength falls faster for the nano ones. The decay method of surface charge and also the modification of detrapping charges in nanocomposite films are affected greatly by the absorbed water.
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