Research On Modification Of Fast-growing Poplar Based On Transpiration

In this paper,Xinjiang poplar was used as the research goals.Using formaldehyde and urea as the modifier,Xinjiang poplar was modified by tree injection method.During the period,Xinjiang poplar stem flow was monitored by Stem flow meter,which the injection time was determined And the injection period was determined by observing the changes of the morphology of the leaves of poplar leaves in Xinjiang.Finally,by testing the mechanical properties and dimensional stability,it is analyzed that the difference between Xinjiang poplar modified wood and blank wood.The conclusion is as follows.(1)The rule of the Xinjiang poplar stem flow in sunny day and cloudy day showed that the stem flow in the sunny day showed a trend to Increase and then decrease,only a turning point appeared when the sunlight was strongest at noon,and the stem flow was weaker in the cloudy day than in the sunny day.Both of them showed a weak stem flow from 20 o'clock to 7 o'clock in the next day,in this time the transpiration of Xinjiang poplar was min.In order to not affected the transpiration of Xinjiang poplar,and the injection test at about 7 p.m.was done.(2)Xinjiang poplar was modified By formaldehyde urea modifier,and the pH value of the modifier was 7.1-7.3,the injection period was 6 days.(3)The flexural strength,flexural modulus and dimensional stability of Xinjiang poplar before and after modification were tested(radial,chord direction,volume absorption and swelling resistance),it is found that the properties of Xinjiang poplar Sapwood improved obviously after modification.When the mole ratio is 1.2,three items are all best,at this time,The flexural strength a4 nd flexural modulus of the lower,middle,and upper parts of the sample are 99.52 MPa,91.97 MPa,81.55 MPa,7461 MPa,7821 MPa and 7062 MPa respectively.The relative blank wood of Xinjiang poplar increases respectively 26.61%,21.27%,14.32%,11.12%,17.57%,12.24%,the chordal,radial and volumetric moisture absorption,swelling resistance and moisture absorption rates of the bottom and middle samples were respectively 9.54%,11.78%,17.08%,16.41%,26.06%,28.19%,32.93%,30.25%,and the closer to the infusion port,the better effect of modification.However,the mechanical properties and the dimensional stability of Xinjiang poplar modified heartwood have not been substantially improved compared with the blank wood.In addition,the mechanical properties of the Xinjiang poplar modified wood in the north and south of the trunk are not obvious.(4)Testing of modified Xinjiang Poplar with mole ratio of 1.2 through SEM,EDX XRD,and FTIR,the modifier entered the cell cavity,cell wall and cell pit.The relative content of nitrogen elements on the surface of the modified wood is 28.95%,The modified wood has increased by 26.69% compared to the blank wood.The crystalline structure of the modified Xinjiang poplar were not changed.When the modifier entered the amorphous region of cellulose,the crystallinity increased,and the increase of the lower,middle,and upper parts of the sample was 3%,2.3% and 1%,respectively.By comparison the modified wood and the blank wood,reduction of characteristic peak of hydroxyl expansion vibration,and the expansion vibration peak of the C-H bond weakened,the absorption peak of amides I band and amide II band also weakened,and the C-O-C was unsymmetrical expansion.The vibration and C-O stretching vibration increased slightly,which proved that the crosslinking reaction between modifier and Wood composition.