RELATIONSHIP OF WOOD SURFACE-ENERGY TO SURFACE-COMPOSITION

The wood cell wall is composed of cellulose, lignin, hemicelluloses, a nd extractives. Thus, the surface energy of the wood material must be some combination of the surface energies of these components. The infl uence of extractives on wood surface chemistry can be important in div erse industrial applications, such as coating, pulping, and wood-based composites. In this study, pine wood meal was subjected to heating, w ashing with toluene, and extraction with acetone/water, dichloromethan e, and ethanol/benzene. The surface properties and composition were th en determined by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and inverse gas chromatography (IGC ). The dispersive component of the surface free energy, the enthalpy, the entropy, and the acid/base interactions were calculated from IGC m easurements and compared to the surface composition as revealed by XPS . Heating and washing with toluene altered surface properties only sli ghtly. Extraction of wood meals with acetone/water, dichloromethane, a nd ethanol/benzene appeared to partially and selectively remove most e xtractives from the wood, resulting in an increased dispersive compone nt of the surface energy, increased acidity, and increased basicity. T he surface energy appeared to be related to the distribution of surfac e oxygen-containing functional groups.