Inverse gas chromatography and XPS of extracted kraft pulps

Kraft pulps at the κ number level of 15 obtained from Acer saccharum (sugar maple) and Eucalyptus globulus prepared with and without hot water extraction (HWE) were analyzed by inverse gas chromatography (IGC) and X-ray photoelectron spectroscopy (XPS). In the case of A. saccharum pulps, the dispersive component of the surface energy ( γ s d ) at 40°C determined by IGC was 39.8 mJ m -2 (control pulp without HWE) and 36.7 mJ m -2 (HWE pulp). Eucalyptus globulus pulps resulted in γ s d values of 30.8 mJ m -2 (control) and 34.9 mJ m -2 (HWE). The higher values of γ s d for sugar maple pulps were interpreted as the influence of lower amounts of extractives or lignin at their surface, as revealed by XPS. It is also discussed why the acid-base character of the sugar maple pulp surface was slightly reduced with previous HWE, whereas, for E. globulus , it was greatly enhanced.