Photochromic Mechanism And Protection Technology Of Dyed Wood Veneer

Photo-chromic mechanism and protection technology are the important scientific problems in the development of plantation wood color modulation. This paper studied the dyed wood veneer and its chemical constituents. The color changing process and response relation of dyed wood veneer under different light source radiation were discussed. The structure changes, light oxidation and degradation mechanism of dyes, ensemble cellulose, lignin, and extractives were investgated. The dyeing matrix acetylation, ultrasonic assisted wood dyeing, transparent water coated were also studied. The main results are as follows:(1) The color change degree increased with radiation time prolong, the discoloration rate was the fastest at early radiation. K/S curves of dyed wood veneer sufferd a downward trend after optical radiation, and the direction of long wave spectral reflectance curve developed. Spectral reflection curve can used to quickly visually assess the light fastness of dyed wood veneer.(2) Dyes and wood chemical structure plays a complex synergy on the selective absorption of different wavelengths of light. The color fastness rate of dyed wood veneer was closely related to dyes, lignin, the optical energy and wavelength of optical radiation.(3) The color change relation of dyed wood veneer under the xenon, ultraviolet and natural light radiation was △E*x=1.095AE*N+3.005, △E*u=0.651 △E*N+1-458. The essence of the acceleration factor is the ratio of optical radiation degree.(4) The dyes suffered photooxidation photodegradation reaction. The light oxidation degradation path of cellulose as follow, cellulose glucose glycosides of base ring-OH (C1), OH (C6), para-OH (C2 and C3), aldehyde-CHO or ketone-C=O, carboxylic acid-COOH. Ultraviolet radiation made some weak dyed veneer fiber surface became more serious degradation, the organizational structure and wood cell wall portion such as the pit membrane was destroyed.(5) The unsaturation structure of the lignin were degraded by of benzene oxygen free radical reaction, the formation of carbonyl or quinone compounds, lignin by recurring benzene oxygen - quinone - light oxidation degradation of REDOX reaction. A linear relationship between the photochromic degree △E* of deyed wood vener and the lignin degradation and the formation of carbonyl group was founded.(6) Ultrasonic auxiliary treatment improved the permeability of wood veneer, created new fluid channels and the dye adsorption sites, and improved the light fastens of deyed wood, which is a gtreat wood dyeing method. Acetylation treatment effectively improved the ability to resist photodegradation of dyed wood and thermal stability. Water-based paint processing light discoloration of woodiness material has good inhibition effect, mainly depends on it inhibited the yellow and blue index b* incressed...