The relation between carbon-fibre surface treatment and the fibre surface microstructure

The effect of an electrochemical surface treatment on the surface microstructure of Tenax® high‐tensile‐strength carbon fibres is investigated using a multi‐technique approach. The fibres are treated in a laboratory set‐up, which simulates the production conditions. The surface functional groups are characterized and quantified, and their dependence on the treatment intensity is determined. The surface chemistry is correlated with the fibre surface topography. It is observed that for increasing treatment intensity, the surface area does not increase significantly (except at very high intensities, in which a porous structure is formed). This contrasts with the dispersive part of the surface energy, which increases with the treatment intensity. Moreover, both basic and acidic surface functionalities are formed, the relative proportions of which change with the treatment intensity. These phenomena can be interpreted in terms of the concentration of active sites, which increases with the surface treatment and may be related to ‘basal plane edges’ of the (disordered) graphitic fibre microstructure.