Charge formation on the surface of a laminated polyimide-fluoroplastic film by direct-current discharge treatment

The effect of a direct-current discharge on the tetrafluoroethylene-hexafluoropropylene copolymer (FP) layer of laminated polyimide-fluorocarbon polymer films (including the commercial film PMF-351) placed in the cathode fall was studied. The magnitude of the negative charge induced in the films was shown to be independent of the film thickness. A thermostimulated relaxation curve for the PMF-351 film exhibited two peaks, one at 484 K due to relaxation of the negative charge in the bulk of the FP layer and the other at 417 K characteristic of negative charge relaxation in the polyimide layer. The results are explained by detrapping of electrons by plasma UV radiation that is not absorbable by the FP layer.