Due to their low surface energy, poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films must be treated by chemical or physical activation methods before using. Among these activation strategies, using sodium naphthalene solution is a popular one. However, the effect of this strategy's chemical activation conditions on the surface properties of the FEP film is rarely discussed. In this study, FEP films were chemically activated by the sodium naphthalene solution with adjusting concentration, solvent, and activation time. With increasing concentration and activation time, many granular substances appeared on the surface of the FEP film. When tetrahydrofuran was used as a solvent, the color of the film gradually turned brown; when 1,3-dimethyl-2-imidazolidinone was chosen as the solvent, the color change was not very significant. The contact angle was significantly reduced from 112° before activation to 26° after activation, and the surface energy was greatly enhanced from 34 mN m-1 before activation to 66 mN m-1 after activation. In addition, compared with the FEP samples treated by Ar plasma, the sodium naphthalene system showed a stronger activation ability. Activated FEP films that suffered from the Ar plasma treatment could still maintain a higher energy surface than that of the pristine FEP.
Keywords: chemical activation; film surface; poly(tetrafluoroethylene-co-hexafluoropropylene); sodium naphthalene solution.