Approaches to Poly(Tetrafluoroethylene) Adhesive Bonding

In this work, we present an approach to achieve improved adhesive bonding with a poly(tetrafluoroethylene) (PTFE) substrate. Surfaces were modified by abrasion, atmospheric air plasma torch (APPT) treatment, and by immersion in basic (NaOH) and strongly acidic/oxidizing (HNO(3)/KMnO(4)) solutions. The wetting properties of the polymer were studied in terms of surface energy, and adhesion tests were carried out using polyurethane, acrylic, and epoxy adhesives. The surface characterisation included surface energy calculation through contact angle measurements, infrared spectroscopy (FTIR-ATR), scanning electron microscopy (SEM), and X-ray electron diffraction (EDX). Adhesion was evaluated by pull-off tests following the UNE EN-24624 standard. Experiments revealed that both oxidation and plasma treatment enhanced surface energy, defluorination, and the creation of a rougher PTFE surface, resulting in adhesion. Simple oxidation and its combination with plasma treatments yielded the higher tensile strength results, with epoxy as the most suitable adhesive among those studied. Samples presented adhesive or mixed type failure modes.