Study On The Effect Of Modification On Physical And Mechanical Properties Of Populus

Wood is a combination of composite materials and porous material properties of composite biomass materials,and today,the natural shortage of rare wood,timber supply and demand in the increasingly tense situation,the rapid development of artificial forest fastgrowing forest to solve this problem One of the effective measures.However,because the fast-growing forest timber usually has a high proportion of young wood,low wood density,physical and mechanical properties are lower than the natural forest wood and other defects,limiting the scope of application of fast-growing wood,so the need for modified wood to make up for the inherent timber Defects,to enhance its practical value.Wood modification research began in the 20 th century,30 years,through chemical,biological or physical and other media acting on wood,enhance the size of wood stability,durability,corrosion and other properties.In recent years,scholars at home and abroad have widely used composite wood such as wood-resin and wood-inorganic materials to prepare composite wood with high strength or special function,and have carried on extensive research and exploration to its physical mechanics.The research on the preparation of wood composites and the macroscopic mechanical properties,dimensional stability,antibacterial property and flame retardancy of the composites were studied.The research on micromechanical properties of wood has just started,and the research object has more use of softwood leaf with thick cell wall.There are few studies on the micro-mechanical properties of broad-leaved wood.Only the complete mechanical testing and research system from macroscopic to microscopic,Can we really grasp the mechanical behavior of wood mechanism.In this paper,the effects of different modification treatments on the physical and mechanical properties of wood were studied by using Populus tomentosa as the research object.(3h,6h,9h)under vacuum conditions were prepared by homemade water-soluble lowmolecular-weight phenolic resin(PF).Before and after the treatment and the differenttreatment time,the poplar was used in the high temperature oven(160 ?,180 ?,200 ?)under the heat treatment modification,by comparing the different temperature of the heat treatment materials and the physical and mechanical properties between the two,so that the immersion treatment and heat treatment can be enhanced Wood performance.The micro-mechanical properties of the wood were tested by nanoindentation testing machine,and the changes of the elastic modulus and hardness of the cell wall were analyzed.Experimental studies show that:1.When the low-molecular-weight phenolic resin is used to impregnate the poplar,the weight of the wood is gradually increased with the increase of the immersion time,the density increases,the physical properties increase and the dimensional stability is improved,indicating that the phenolic resin has the physical properties Enhance the effect.When the temperature was increased,the weight of the wood decreased with the increase of the treatment temperature.The density of the wood decreased with the increase of the treatment temperature,and the wood was evaporated in the high temperature environment.The antiswelling performance is improved and the dimensional stability is improved,which indicates that the heat treatment has a certain effect on the physical properties of Populus tomentosa.2.When the low molecular weight phenolic resin was used to impregnate the poplar,the hardness of the wood surface increased with the immersion time,and the cell wall elasticity increased.The mechanical properties of Populus tomentosa were improved after the modification of low molecular weight phenolic resin,and the macroscopic and microscopic mechanical properties were consistent.The results showed that the mechanical properties of P.bidentata were improved after the modification of low molecular weight phenolic resin.Cell wall enhanced cell wall mechanical properties.Thus the overall performance of the wood is improved.When the heat treatment technology was used to modify Populus tomentosa,the hardness of wood was almost unchanged with the increase of treatment temperature.The hardness and elastic modulus of wood were reduced at 160 ?,which was due to the low temperature The main loss of wood components of wood moisture and volatile substances,an increase of wood brittleness,and thus the hardness of wood decreased.In the hightemperature environment of 180 ? and 200 ?,the hardness is enhanced,which is due to the high temperature environment caused by macromolecular substances such as cellulose degradation,wood hardness has been enhanced;Overall,the wood cell wall hardness changes Not the same,and the wood surface hardness trends basically consistent.After the heat treatment,the mechanical properties of Populus tomentosa were slightly decreased,and the macroscopic and micro-mechanical properties were consistent.The results showed that the mechanical properties of the poplar were reduced after heat treatment,and the wood properties were reduced by heat treatment.3.Phenolic resin due to contain very easy to oxidize into a brew of silver and reddish brown,so that the color of impregnated phenolic resin darker,changed the original color of poplar.High temperature heat treatment of Populus to wood surface carbonized material color from light yellow to brown,and with the temperature rise of the deeper the color of wood,after heat treatment of wood wood is more prominent.In summary,through the immersion treatment and heat treatment technology of wood can enhance the physical and mechanical properties of wood to make up for its inherent defects,to play its advantages to replace the use of some natural wood,the production practice will have important practical significance and practical value.