Study On The Preparation And Properties Of Dyed Chinese Fir Compressed Wood

Wood dyeing is an important way to improve the utilization value of low-value wood.However,simple dyeing can not effectively improve the mechanical properties of wood,so the dyed wood needs to be enhanced.In this paper,acid dyes were used to firstly vacuum and pressure impregnate the fast-growing fir wood,and then compressing enhancement,and the effects of moisture content,hot pressing temperature,holding time and compression ratio on the deformation recovery rate,density,and texture compressive strength and color of dyed compressed wood were discussed by single-factor method,the influence of various factors on the performance of dyed compressed wood was analyzed by orthogonal test method,and the compressing process was optimized by fuzzy mathematical comprehensive evaluation method.Through the analysis of the fixing effect of iron oxide red,melamine formaldehyde resin and dimethyl diallyl ammonium chloride,the appropriate fixing agent was selected and the dosage was determined.Characterize stained media before and after compression using scanning electron microscopy,x-ray diffraction,Fourier infrared spectroscopy,and thermo-gravimetric analysis.The main conclusions of the paper are as follows:(1)Under the influence of moisture content,hot pressing temperature,holding time and compression ratio,the deformation recovery rate,density and compressive strength of dyed compressed wood before compressing are different from those of Chinese fir compressed wood,but under the same conditions,the deformation recovery of dyed compressed wood decreases,and the density and compressive strength of compressed wood are also greater than that of Chinese fir compressed wood.Different conditions have different effects on the color of dye compressed wood,and the moisture content and compression ratio before compressing have little influence on the color difference change,and the hot pressing temperature and holding time have a greater impact.Under the test conditions,the suitable compressing process range of dyeing wood is: moisture content before compressing20%-80%,hot pressing temperature150-210°C,holding time0.5 h-2 h,compression ratio20 %-50 %.(2)The effects of hot pressing temperature,holding time and compression ratio on the compression set recovery rate of dyed compressed wood were very significant,the compression ratio had significant effects on density,compressive strength and flexural strength,and the moisture content before compression had significant effects on flexural strength.Using the fuzzy mathematical comprehensive evaluation to comprehensively evaluate the five indicators,the optimal compression process of dyed wood was determined as follows: moisture content before pressing 50%,hot pressing temperature 150°C,holding time 1.5h and compression rate 50%.(3)Compared with iron oxide red and DMDAAC,MF resin has the best comprehensive performance of dye compressed wood after fixation;With the increase of the mass fraction of MF resin,the color fastness was significantly improved,the deformation recovery was significantly reduced,and the mechanical properties were generally improved,but after the mass fraction was higher than 15%,the change of each property slowed down.Therefore,considering the comprehensive performance and cost,the amount of MF resin should not exceed 15%.(4)There was no obvious difference in the microscopic morphology of the dyed wood and the Chinese fir wood after compressing,but after fixing by MF resin,the dye was coated by the cured resin and fixed in the wood,so that the deformation recovery of the dyed and compressed wood was significantly reduced,and the color fastness and mechanical properties were improved;In the FTIR spectra after resin treatment,the positions of O-H,C=C and C=O characteristic absorption peaks did not change significantly,but the peak intensity was weakened,and triazine ring absorption peaks appeared.Compared with the Chinese fir wood and dyed compressed wood,the crystallinity of MF resin fixed color wood before and after compression is increased.The synergy of compression and resin further improves the thermal stability of fixed color compressed wood compared with that of dyed wood.