Abstract: Composites of perfluorinated ethylene-propylene copolymer (FEP) with Ti02 and Al2O3 were prepared via thermoforming. the effects of oxide content on dielectric constant, dielectric loss, and high-frequency breakdown performance of the composites were studied. the dielectric constant and loss of FEP composites increased with increasing oxide content, with the influence of Ti02 being more obvious. Ti02 possessed a negative effect on the high-frequency breakdown performance. At 4. 0 wt，the damage threshold of FEP/Ti02 composite was only 48. 9%that of neat FEP. In contrast, the high-frequency breakdown performance increased with increasing Al2O3 content. When the content of Al2O3 was 1 .2 wt，the damage threshold of FEP/Al2O3 composite reached 313 J/m2，that was twice that of neat FEP.

Key words: fluorinated ethylene propylene, titanium dioxide, aluminum oxide, dielectric performance, high-frequency breakdown performance