Influence of the curing temperature on the diffusion rate of the perfluorinated alkyl chains of a modified epoxy resin

[Display omitted] •Surface properties of a fluorinated epoxy resin depend on the curing temperature.•Diffusion of grafted perfluorinated compounds was monitoring during the resin curing.•Fluorine accumulation was observed at both air and substrate interfaces. Perfluorononanoic acid (F17) was grafted to an epoxy resin. The virgin epoxy resin and the fluorinated epoxy resin were cured at various temperatures. Both air-resin and substrate-resin interfaces of the cured materials were characterized in terms of: (i) free surface energy, (ii) surface composition, evaluated using angle-resolved X-ray photoelectron spectroscopy (AR-XPS). Fluorine proportion was quantified at probing depths of about 4.5 and 9nm. The curing temperature highly influenced the diffusion of the perfluorinated chains towards both interfaces. Depending on the curing conditions, very low free surface energies (17mJ/m2) due to high fluorine concentrations (fluorine/carbon ratio=0.6) were measured at the air-resin interface. However, the F17 diffusion towards the substrate was also observed and led to important fluorine concentrations (F/C up to 0.4). Finally, a two-step curing procedure was used for monitoring the F17 diffusion during the curing, illustrated by an accumulation of fluorine atoms at both interfaces. A non-linear relation was highlighted between the surface energy drop and the fluorine content measured by AR-XPS.