The Complex Permittivity of Polyethylene/Mica Composites

The complex relative permittivity ¿*(f) of polyethylene/mica composites has been measured in the frequency range 10-2 to 107 Hz, as a function of mica content ¿2 and prior sample conditioning. ¿*(f) was found to display two main features: ¿´-¿´ ¿and K´´ vary as fn-1 with 0.64¿n¿0.83 for all ¿2, on account of the intrinsic dispersive properties of the mica. In addition, K´´ displays a broad peak centered in the audio frequency range, associated with ¿Maxwell-Wagner-Sillars¿ losses due to absorbed water. Finally, the high frequency permittivity K´Â¿ is compared with various ¿mixture formulae in the literature; Sillars´ theory is found to fit experimental data well, even at high ¿2 values.