Surface passivation of epoxy resin with a covalently adhered poly(tetrafluoroethylene) layer

Surface passivation of epoxy resin with a covalently adhered poly(tetrafluo roethylene) (PTFE) layer was achieved by casting the epoxy resin on a surfa ce-modified PTFE film, followed by thermal curing and mechanical delaminati on. Surface modification of the PTFE film was carried out by argon plasma p re-treatment, followed by UV-induced graft copolymerization with acrylic ac id (AAc), glycidyl methacrylate (GMA), 2-hydroxyethyl methacrylate (HEMA) a nd acrylamide (AAm), The compositions and microstructures of the correspond ing AAc-g-PTFE, GMA-g-PTFE, HEMA-g-PTFE and AAm-g-PTFE surfaces were charac terized by X-ray photoelectron spectroscopy (XPS) and water contact angle m easurements, respectively. In all cases, the graft yield increased with the argon plasma pre-treatment time of the PTFE film and the monomer concentra tion. Thermal curing of the epoxy resin on the graft-copolymerized PTFE sur faces (the AAc-g-PTFE and GMA-g-PTFE surfaces, in particular) resulted in s trong adhesion of the epoxy resin on the PTFE surface. The strong adhesion arose from the curing of the grafted AAc or GMA chains into the epoxy resin matrix to form a highly cross-linked interphase, as well as the fact that the AAc or the GMA chains were covalently tethered on the PTFE surfaces. Th e strong adhesion also resulted in cohesive failure inside the PTFE substra te during mechanical delamination to give rise to a passivated epoxy resin surface with a covalently adhered PTFE layer. (C) 2001 Elsevier Science B.V . All rights reserved.