Surface modification of bi-axially expanded poly(tetrafluoroethylene) by plasma polymerization of ethylene

In this study, the plasma polymerization of ethylene has been used to deposit a polyethylene (PE)-like thin layer on the surface of the selected expanded poly(tetrafluoroethylene) (ePTFE) films. To evaluate the activity of the PE-like surface, acrylic acid (AAc) graft polymerization was carried out for the pretreated films. The modified ePTFE films were characterized by X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopies. The surface morphologies of the films were investigated by scanning electron microscopy and atomic force microscopy, and the wettability was evaluated with the sessile drop method and Wilhelmy plate method. It was found that the PE-like surface of the plasma treated specimen can be further grafted by AAc implying that the deposited surface remained active sites. After grafting by AAc, the advancing contact angle (θa) and the receding contact angle (θr) decreased approximately 40° and 50°, respectively, exhibiting an improvement of the surface hydrophilicity for the modified ePTFE specimens. It was also found that the lap shear strength of the polyAAc–grafted ePTFE specimen, adhered between two stainless steel surfaces by a selected epoxy resin, was enhanced by approximately three times.