Preparation And Properties Of Strengthened-dyed Compound Modified Cunninghamia Lanceolata Wood

Chinese fir?Cunninghamia lanceolata?is one of the important fast-growing species in the south China,but its planted wood has many defects such as low density,low intensity,unstable dimensions and poor decoration,which greatly limit its value-added utilization.In this paper,the planted Chinese fir wood was modified through an integrated strengthening-dyeing technology,its density,mechanical strength,dimensional stability and decoration performance all increased simultaneously.First,based on water soluble Melamine modified urea formaldehyde resin?MUF?,the effects of compounding dye types,solution pH values,dye mass fraction,dye adding ways and dyeing auxiliaries on compound solution and treated wood's properties were investigated.Second,the preparation technology was optimized by orthogonal experiments.Finally,the strengthening and dyeing mechanism of compound strengthened-dyed modified wood was discussed through scanning electron microscopy?SEM?,nano-intention test,fourier transform infrared spectroscopy?FTIR?and X-ray photoelectron spectroscopy?XPS?analyses.The main conclusions were as follows:1.Based on self-made water-soluble melamine-urea-formaldehyde resin?MUF?,through the single factor analysis,acid red G had the best compatibility and dyeing properties in eight dyes;as for three dyeing auxiliaries,Na₂CO₃ had the best compatibility and color fastness.Under the conditions of acid red G,1%dye mass fraction,1%Na2CO3 mass fraction and direct blending,the compound strengthening-dyeing modifier was obtained,which had long storage life,good stability,obvious and even dyeing effect.2.The mass fraction of resin,dye and Na2CO3 and the resin curing temperature were selected as four factors to carry out an orthogonal test L₉?3⁴?.Based on a comprehensive evaluation,the optimum modification condition was:30%MUF mass fraction,1%dye mass fraction,0.5%Na₂CO₃ mass fraction and 100?curing temperature.3.The physical and mechanical properties of compound modified wood was significantly improved.After Chinese fir wood being treated with the optimum compound modifier,its density,MOE,MOR and compressive strength increased by 61.0%,48.5%,95.7%and 83.2%respectively,its ASE reached over 70%,and the dyeing effect was good with a total color difference exceeded 50 NBS.Compared with wood dyed in water solution,the color of compound dyed wood was more even and bright,and was of better color fastness.4.The compound modifier was well impregnated into the wood,and the pits and voids of vessels' cell wall were completely covered with the modifier,thus improving physical and mechanical properties of wood.The hardness and elastic modulus of the cell wall were increased by 95%and 100%respectively.The spectra absorption peak position and intensity of compound modified wood was consistent with those of MUF modified wood.The compound modifier interacted with wood in two ways:chemical bonding and physical filling.Light aging of untreated wood and MUF modified wood was mainly caused by lignin and extract components,while light aging of water dyed wood and compound dyed wood was mainly caused by dye molecules.