Ageing of plasma-treated poly(tetrafluoroethylene) surfaces

Highly hydrophobic poly(tetrafluoroethylene) (PTFE) surfaces were modified with an air glow discharge plasma to improve their wettability. However, th e hydrophilic character obtained diminishes with time, due to molecular mov ement in the polymer. We have determined that the ageing process is strongl y affected by the environment and temperature in which the surfaces are sto red. A hydrophobic environment and high temperatures promote faster recover y of the original properties of PTFE than low temperatures. Nonetheless, a hydrophilic environment, even at high temperatures, prevents the surface fr om losing the polar character obtained from the plasma treatment, stopping the ageing process. Moreover, this process is reversible since the characte r of the treated surface changes when the environment changes (i.e. from wa ter to air). The hydrophilicity of the surfaces was evaluated by contact an gle measurements of a droplet of water.