Contributions of Extractives and Lignin to the Fractal Geometry of Inter-nal Wood Surfaces

Internal wood surfaces can be treated as fractals, which are between Euclidean geometry and complete randomness. The fractal dimension D_fs is very informative in investigating the roughness of the internal surfaces of wood. In this study, the water sorption isotherms, including adsorption and desorption isotherm, of untreated, benzene-alcohol extracted and delignified (after benzene-alcohol extracted) spruce (Cuninghamia lanceolata) were measured at 30℃. On the basis of these isotherms, the D_fs values were calculated by FHH equation, which is based on multimolecular sorption. The results showed that both groups of D_fs values (respectively calculated from adsorption and desorption isotherms) of untreated, benzene-alcohol extracted and delignified wood have same order, that is, untreated > benzene-alcohol extracted ≈ delignified. Therefore, the conclusion can be made that the benzene-alcohol extractives have significant contribution to the fractal geometry of internal wood surfaces. Lignin also has influence on the fractal geometry, but this influence is very small while compared with that of the extractives. Moreover, the D_fs values calculated from adsorption isotherms are bigger than those from desorption isotherms.