The Complex Permittivity of Polyethylene/Mica Composites

The complex relative permittivity ĸ*(f) of polyethylene/mica composites has been measured in the frequency range 10-2 to 107 Hz, as a function of mica content υ2 and prior sample conditioning. ĸ*(f) was found to display two main features: ĸ'-ĸ' ∞ and K'' vary as fn-1 with 0.64⪯n⪯0.83 for allυ2, 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'∞ is compared with various "mixture formulae in the literature; Sillars' theory is found to fit experimental data well, even at high υ2 values.