The Study On The Wood Microwave Pre-treatment And Ultrasonic Dyeing

It was studied that the connectivity between wood cells increased and the permeability of wood improved with the microwave radiation pretreatment, which changed the wood micro-structure. This paper uses poplar(Populous tremula), birch(Betula platyphylla) and oak(Querus mongolica) as test material treated by microwave radiation and vacuum pressure dyeing, takes the mass-increasing rate and the dye-uptake as research object, studies the effects and regulations of pre-treatment conditions on the permeability and dye-ability, such as wood moisture content, microwave processing time and microwave radiation power, presents the difference of permeability and dye-ability between poplar sapwood and heartwood, birch flat-sawn board and quarter-sawn, optimizes the process of poplar, birch and oak microwave pretreatment with orthogonal test. Dyeing with ultrasonic is different from wood convention dyeing, an unusual environment established by the cavities implosion generating high temperature, high pressures and high speed jet. This paper studies the effects and regulations of ultrasonic power, birch veneer thickness and ultrasonic dyeing concentration on the dye up-takes, optimizes the ultrasonic dyeing process birch veneer (3mm) with orthogonal test, investigates ultrasonic dyeing mechanism dynamically and thermodynamically, analyzes micro-structure changing of birch veneers dyed by ultrasonic and chemical composition by FTIR.(1) The permeability and dye-ability of poplar, birch and oak are influenced by wood moisture content, microwave processing time and microwave radiation power, and there are some regular distributions between them: at the point of the moisture content about 30%, the mass-increasing rate and dye-uptake of the poplar, birch and oak are biggest, namely the dyeing effect is best; compared to the untreated wood, the mass-increasing rate and dye-uptake of the poplar, birch and oak has the distinct enhancement and increases with increasing microwave power; when the microwave power is 23.8kw, the mass-increasing rate of the poplar heartwood, sapwood respectively increased by 37.83% and 86.71%, and dye-uptake increased by 86.49% and 22.64% compared to untreated wood.(2) The mass-increasing rate and the dye-uptake taken as research object, based on the results of variance analysis with statistical analysis system(sas), optimized process are given of poplar, birch and oak treated by microwave radiation and vacuum pressure dyeing. It is concluded that mass-increasing rate and the dye-uptake of poplar, birch and oak is the biggest at the moisture content of 30% control, microwave irradiation power of 23.8kw, microwave irradiation time of 35s; the moisture content of wood has the most significant influence on the mass-increasing rate; the microwave treatment time has the most significant influence on the dye-uptake.(3) The temperature of the ultrasonic dyeing has the most significant influence on the wood dye-ability, the dye-uptake of birch veneer is the biggest at 80℃; the dye-uptake increases with the ultrasonic dyeing time, and the optimized dyeing time is 6h,; the ultrasonic frequency has little influence on the the dye-uptake, and the optimization of ultrasonic frequency is 45kHz. the main influence factors of the dye-uptake are sorted: temperature of the ultrasonic dyeing> ultrasonic dyeing time > ultrasonic frequency. The ultrasonic dyeing of the 3mm thickness birch veneer pretreated with the microwave radiation is level dyeing.(4) By the means of thermodynamic analysis, it is concluded that: at the same dyeing temperature, the dye-uptake and dyeing rate with the method of ultrasonic dyeing are higher than them with the method of convention dyeing, the dyeing affinity and dye-uptake of acid red GR are improved by the method of ultrasonic dyeing.(5) By the means of dynamical analysis, it is concluded that: at the same dyeing temperature, the dye-uptake and dye diffusion coefficient with the method of ultrasonic dyeing are higher than them with the method of convention dyeing anytime. The dye diffusion coefficient of 80℃ultrasonic dyeing increased about 61.87% than it of 95℃convention dyeing. The diffusion activation energy of acid red GR with the method of ultrasonic dyeing and convention dyeing is, respectively, 10.43kJ/mol and 13.95kJ/mol, diffusion activation energy decreased by 33.81%.(6) SEM Observation of the birch veneer (3mm) with the method of ultrasonic dyeing showed that the wood texture of the surface is loose, the pores and gaps existing among the fibers increase, and the specific surface area of dyeing enlarged significantly, adsorbability to dye enhanced.; cracks on the pits of birch veneer after ultrasonic dyeing expand and increase, then the effective permeability channels increase. (7) FTIR Spectrum Analysis of the birch after ultrasonic dyeing or convention dyeing, with the method of ultrasonic dyeing , absorption intensity of the characteristic absorption peak of the cellulose(wave number 2900 cm-1,1425 cm-1,1370 cm-1 and 895 cm-1), the characteristic absorption peak of the lignin (wave number 1590 cm-1,1510 cm-1,1460 cm-1 and 1650 cm-1 ), the characteristic absorption peak of the hemicellulose (wave number1744 cm-1,1330 cm-1 and 1237 cm-1 ) are less than them with the method of convention dyeing. It shows that structure destruction with the method of ultrasonic dyeing is more significant than it with the method of convention dyeing.