Grafting of epoxy resin on surface-modified poly(tetrafluoroethylene) films

An epoxy/PTFE composite was prepared by curing the epoxy resin on the surfa ce-modified PTFE film. Surface modification of PTFE films was carried out v ia argon plasma pretreatment, followed by UV-induced graft copolymerization with glycidyl methacrylate (GMA). The film composite achieved a 90 degrees -peel adhesion strength above 15 N/cm. The strong adhesion of the epoxy re sin to PTFE arose from the fact that the epoxide groups of the grafted GMA chains were cured into the epoxy resin matrix to give rise to a highly cros slinked interphase, as well as the fact that the GMA chains were covalently tethered on the PTFE film surface. Delamination of the composite resulted in cohesive failure inside the PTFE film and gave rise to an epoxy resin su rface with a covalently-adhered fluoropolymer layer. The surface compositio n and microstructures of the GMA graft-copolymerized PTFE (GMA-g-PTFE) film s and those of the delaminated epoxy resin and PTFE film surfaces were char acterized by X-ray photoelectron spectroscopy (XPS), water contact angle an d scanning electron microscope (SEM) measurements. The delaminated epoxy re sin surfaces were highly hydrophobic, having water contact angles of about 140 degreesC. The Value is higher than that of the pristine PTFE film surfa ce of about 110 degrees. The epoxy resin samples obtained from delamination of the epoxy/GMA-g-PTFE composites showed a lower rate of moisture sorptio n. All the fluorinated epoxy resin surfaces exhibited rather good stability when subjected to the Level 1 hydrothermal reliability tests.