Surface-charging behavior of plasma-treated polymer films

Thin films of the Teflon^TM homo- and copolymers TFE, FEP, PFA, MFA, AF, and PVDF-TFE (VF₂-VF₄) were treated with a microwave plasma in hydrogen or argon, and charged with a point-to-grid corona. It was found that a hydrogen-plasma treatment has a greater influence on charge stability than an argon-plasma process and that the stability of plasma-treated and negatively charged fluoropolymers is lower than that of untreated samples, while the stability of plasma-treated and positively charged fluoropolymers is higher. X-ray photoelectron-spectroscopy showed ablation of fluorine and incorporation of oxygen- and nitrogen-containing groups into the surface. Furthermore, Teflon-PFA and polyethylene terephthalate (PETP) samples were charged in a radio-frequency argon plasma by way of self-biasing. In this case, the charge level increases with increasing bias and charging time. However, enhanced sample heating must be taken into account at higher plasma power. With a plasma, PFA can be charged to higher initial values, but PETP shows better charge stability