The surface chemistry and acid–base properties of a PAN-based carbon fibre Original Research Article

Akzo Tenax HTA carbon fibres (high strength) with progressive amounts of the standard commercial treatment have been investigated using a number of surface analytical methods. Chemical content and structure have been interrogated by XPS and ToF-SIMS, and compared to thermodynamic and acid–base properties probed by IGC and DCAA. The γsd values of the fibres were calculated at ca. 50°C and were found to decrease from 104 mJ m−2 for untreated fibres to 78 mJ m−2 for 200% oxidised fibres. The acid–base character at the molecular level and the macroscopic properties of γsp are significantly enhanced even at low levels of oxidation, resulting in increased wettability of carbon fibres by polar species. Wettability of the surface by non-polar species appears to be largely unaffected by oxidation. XPS analysis reveals that oxygen is introduced progressively at the expense of carbon content, and trace amounts of Na and Cl slowly increase with oxidation. ToF-SIMS shows that the amount of Ca and Na increases very quickly during the early stages of oxidation, whereas Cl and O increase at a more steady rate.