Study On Process And Fixation Mechanism Of Poplar Wood Modified With Sodium Silicate/Acrylic Emulsion

The defects of poplar,such as low density,low strength,soft material and poor dimensional stability,greatly limit its application range.Therefore,poplar is modified to improve its practical value.In this paper,the wood of populus tomentosa as the research object,with sodium silicate solution as the main agent,through vacuum and pressure impregnation and cyclic pressure impregnation on the poplar wood modification,with the help of single factor experiment and orthogonal test,obtained the optimal process of sodium silicate cyclic pressure impregnation modification of poplar wood.Based on the curing principle of sodium silicate,in the process of cyclic pressure impregnation,the curing agent is introduced to form a double agent diffusion with sodium silicate,and the curing reaction occurs in the wood to produce SiO2 and insoluble substances,so as to enhance the loss resistance of the modified wood.Using acrylic emulsion to dry film forming characteristics,it can be further modified with sodium silicate to poplar wood to further improve the water resistance of modified wood.The mechanical and thermal properties of the modified materials were tested.Finally,the fixation mechanism of the modifier was explored by a series of characterization methods.The main conclusions are as follows:(1)The results of four factor and four level orthogonal test showed that the significant order of the influence of each factor on the mechanical properties of the modified wood was:impregnation solution concentration>impregnation time>impregnation pressure>cycle times.The optimized process is as follows:the concentration of Na2SiO3 solution is 40%,the impregnation time is 4 h,the impregnation pressure is 0.5 MPa,and the number of cycles is 3.The test results of mechanical properties show that after sodium silicate modification,the compressive strength and end face hardness of poplar material are greatly improved,except that the flexural strength is reduced.(2)The results of sodium silicate modified poplar treated with different reagents show that the water absorption and silicon loss rate of the cured modified wood are effectively reduced,in which sodium bicarbonate is the best as the curing agent,and maintains the best physical and mechanical properties and heat resistance at the same concentration level.The results of curing modification of sodium bicarbonate solution with different concentrations show that the curing effect of sodium bicarbonate solution with 3%mass fraction is the best.(3)When the mass fraction of acrylic emulsion is 5%,the effect of sodium silicate/sodium bicarbonate and acrylic emulsion on poplar is the best.At this time,the size stability of composite modified material is enhanced,water resistance and drainage resistance are further improved,the swelling resistance of the modified material reaches 43.3%,and the silicon loss rate is reduced to 4.4%.Acrylic emulsion was dried inside the wood to form film,and the wood structure and modifier were encapsulated.(4)The strength grade of acrylic emulsion/sodium silicate/sodium bicarbonate composite modified material reaches TB20,and the flame retardant property reaches the level of flame retardant I.It is proved that the fixation mechanism of modifier in wood is the combination of physical filling and chemical crosslinking.A large number of solid insoluble substances exist in the wood conduit in the form of columns to support the wood structure and increase the wood strength.Some modifiers are bonded with wood components to enhance the stability of composite modified wood.The sealing effect of acrylic emulsion further improves the water resistance and loss resistance of composite modified wood.