Abstract
High-temperature polyimide composites with low and stable dielectric properties were produced by thermally curing prepolyimide moulding compounds which were prepared by the wet impregnation of chopped short quartz fibres with a PMR-II polyimide matrix resin solution, followed by the evaporation of the solvent with vigorous stirring. The mechanical properties, thermo-oxidative stability as well as the dielectric and electric properties of the composites were studied. The experimental results showed that the composites exhibit outstanding mechanical properties and excellent thermal and thermo-oxidative stability at temperatures as high as 371 °C. It was revealed that both the dielectric constant (∼3.0) and loss tangent (∼10−3) of the composites were not obviously changed with a frequency in the broadband wavelength (1 kHz–20 GHz).
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