Melamine Modification of Acetylated Spruce Wood

Acetylation and melamine resin impregnation has shown considerable potential to improve a number of wood properties, among dimensional stability and surface hardness. A combination of these two modification methods may lead to a product that shows the advantages of both. In this study, the uptake of melamine resin into cell walls of acetylated spruce wood and effects of this treatment on compression strength perpendicular to grain were studied. For this purpose, spruce samples were infiltrated with a melamine resin after acetylation to various weight gains. Using the high absorbance behaviour of melamine in ultraviolet light, spectra were recorded with a Zeiss MPM 800 spectrophotometer microscope at measuring spot sizes as small as 1 mu m. Transverse sections with a thickness of 1 mu m were prepared from the specimens after embedding in epoxy resin. Taking advantage of the proportionality between resin concentration and absorbance, estimates of melamine concentrations in the cell walls were possible. To express the amount of resin penetrated into cell walls, a spectral quotient of the absorbances at 241 and 281 nm was defined, the assumed maxima of melamine and lignin, respectively. Acetylation to various weight gains prior to melamine impregnation did not significantly affect melamine uptake into cell walls. As a conclusion, a combined treatments will not suffer from any negative drawbacks. Compression tests normal to the grain were performed and large increases in compression strength as well as modulus of elasticity (MOE) were seen after melamine impregnation. The acetylated specimens seemed to have increased in brittleness compared to the unacetylated reference.