Preparation And Performance Of CaCl₂-NaCO₃ Internal Reaction Deposition Modified Poplar

Wood is the only sustainable building material resource among the four major building materials.It is also one of the indispensable green materials for the construction and economic development of a country.The world's wood supply is still in short supply.Nowadays,the restrictions on cutting and logging,foreign timber export restrictions,and the increasing domestic demand have kept the domestic demand for timber resources high.The fast-growing forest poplar has the advantages of large yield and fast growth.Fast-growing wood is one of the important choices for obtaining wood resources.However,the fast-growing poplar wood is generally low in softness,hardness,strength and density,and is prone to warp deformation and poor dimensional stability,so its range of use is limited.This paper takes poplar timber as the research object,through two-step vacuum-pressure impregnation,to discuss the modification process and mechanism analysis of calcium chloride and sodium carbonate internal reaction deposition modified poplar.To study the weight gain rate,microstructure,mechanical properties and crystal structure of the modified specimen under different solution concentrations,in order to select a more suitable concentration range for further research and to discuss the mechanism of impregnation modification.Through the L₉?3⁴?three-factor three-level orthogonal experiment,the micro-morphology,weight percent gain rate,transverse hardness,tangential hardness,radial hardness of the modified specimen were analyzed,and the preparation process was optimized respectively to obtain a better modification condition.According to the superior hardness of the chord surface,the modified poplars were prepared with more suitable vacuum-pressurized filling modification treatment conditions.Combined with phenolic resin adhesive and urea-formaldehyde resin adhesive,this paper studies the comprehensive properties of modified specimens.This article compares and analyzes the microstructure,crystal structure,chemical functional groups,contact angle and surface free energy,bonding performance and combustion performance of the modified poplar timber.The specific conclusions are as follows:?1?Through a single factor experiment,investigate the effect of vacuum-pressure impregnation on the modification treatment of poplar timber specimens.The results show that the weight percent gain rate of the modified specimen increases with the increase of the concentration of the impregnation solution.The SEM results showed that calcium carbonate filled the catheter wall and wood fiber densely,and was spherical and rhombic calcium carbonate.When the concentration of the impregnation solution is 1.5 mol/L and 2.0 mol/L,the particle size distribution of calcium carbonate of the modified specimen is the narrowest and the particle size distribution is relatively uniform.Under the condition that the concentration of the immersion solution was 2.0 mol/L,the hardness of the transverse hardness,tangential hardness,radial hardness,flexural strength and flexural elastic modulus of the modified specimen reaches the maximum,and the dimensional stability is the best.Through the analysis of the crystallinity of cellulose,the results showed that the crystallinity of the modified specimens decrease with the increase of the concentration of the impregnation solution compared with the unmodified specimens,when the concentration of the impregnation solution is 2.0 mol/L,the crystallinity of the modified specimens decreased the least.The crystal structure determination and phase analysis showed that the calcium carbonate in the modified specimen is mainly vaterite type,aragonite type and calcite type.?2?Taking the concentration of impregnation solution,pressurization pressure and pressurization time as the three factors,three levels were used to design the orthogonal test.The results show that the significant order of the influence of each factor on the mechanical properties of the modified specimen is:the impregnation solution Concentration,pressurized time,pressurized pressure.When the concentration of the impregnating solution is 2.0 mol/L,the pressing pressure is 0.6 MPa and the pressing time is 40 min,the tangential hardness of the wood modified specimen is the best.?3?The modified poplar sawn timber was prepared under the modified conditions of the best tangential hardness of the modified specimens.The results showed that calcium carbonate is venly and densely distributed on the wall of the catheter,the wood rays and the pits connecting the two.The morphology is mainly diamond and spherical,and the calcium carbonate crystals are vaterite,aragonite and calcite.The characteristic peaks of calcium carbonate appear in the middle of which the absorption peaks at 873 cm^-1 and 712 cm^-1wavenumbers are characteristic peaks of CO₃^2-.?4?PF adhesive and UF adhesive were used to make the bonding performance separately,in order to explore and improve the bonding performance of the modified poplar.The results showed that the water contact angle and surface free energy of the modified specimens decreased slightly compared with the unmodified specimens.The contact angle of diiodomethane in the modified specimens is 24.82%higher than that of unmodified specimens.Sanding and purging the surface of the modified specimens to reduce the surface roughness of the modified specimens and effectively improve the wood breakage rate and bonding performance of the modified specimens.The shear strength of the two adhesives of the modified sanding specimens was slightly lower than that of the unmodified specimens.?5?Study the combustion performance of modified and unmodified specimens.The results show that the Heat release rate of modified specimens is reduced,and CO₂ generation rate is increased,which promotes the formation of charcoal and can effectively suppress the smoke generated during the combustion process.The modified specimen has excellent flame retardant and smoke suppression performance.