MODIFICATION OF POLYIMIDE FILMS OF DIFFERENT THICKNESS IN A DIRECT-CURRENT DISCHARGE

Modification of polyimide films of different thickness (25, 40, and 50 mu m) in a de discharge in an air atmosphere was examined. It was fou nd that polyimide film thickness had no effect on the contact angle (t heta) with the same conditions of sample treatment and storage. The su rface potential (phi) significantly depended on the thickness of modif ied films: the greater the film thickness, the greater the absolute va lue of phi, which is negative in sign. The permittivity (epsilon) for polyimide samples of different thickness was measured experimentally. It was found that epsilon = 3.2 +/- 0.2, regardless of the conditions under which the films were modified and stored. The surface charge den sity (Q) was calculated using the formula for a plane capacitor and th e experimental epsilon values. A correlation between the theta and Q v alues for polyimide films of different thickness was found.