Modification of polytetrafluoroethylene porous membranes by electron beam initiated surface grafting of binary monomers

Polytetrafluoroethylene (PTFE) porous membranes were pre-irradiated by electron beam in vacuum. And then the hydrophilic sulfonate groups were introduced by the single step grafting method with binary monomer solution of acrylic acid (AAc) and sodium 4-styrenesulfonate (SSS). The effect of monomer concentration and irradiation dose on degree of grafting, the surface morphological and chemical changes after grafting reaction, as well as the surface hydrophilicity of the modified membrane, were investigated. The surface chemical change was determined by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Morphological changes on the film surface were described using field emitting scanning electron microscopy (SEM). The surface hydrophilicity of the modified film was characterized through water contact angle measurement. The degree of grafting changed with different AAc contents in binary monomers and irradiation doses, and the water contact angle of the film surface reduced significantly when compared with the original one. These results indicated that the grafted polymer layer introduced hydrophilic groups to PTFE membrane and improved the hydrophilicity of the porous membrane. (C) 2009 Elsevier B.V. All rights reserved.