The Improvement Of The Continuous Hot Press And Studying On The Reconstituted Square Lumber

Agriculture and forestry straw remains and wood-base panels were excellent substitute materials to wood.Bccause of some advantages such as wide range of materials,conservation of resources,and environment friendly receive people's attention.Reconsolidated square material using straw as one of them also has a broad development perspective.In this paper,through the improvement on hot press productiong and exploration of hot pressing process,summarized the hot pressing process of reconsolidated square lumber in order to establish the foundation for popularization and application,test mechanical properties and weatherability from reconsolidated square lumber for provide the basis on application.The major results are as below:(1)On the basis of trial manufacture of continuous hot press producting on reconsolidated square lumber,Lengthen the side pressure device from 2 meters to 10 meters which ensure that reconsolidated square lumber was suffered side pressure during the whole hot pressing process and the quality of reconsolidated square lumber;increased the side tension tension device can prevent the side-pressure chain elongating and falling during the hot pressing process,improve the safety and reliability of the press producting;used dynamic balance nuts and static balance nuts to adjust the strip in order to solve the deviation problem that can make hot press producting prepared reconsolidated square lumber in normal.(2)The better continuous hot pressing process with reconsolidated square lumber is:cotton stalk after softening treating,fluffer and peeling,drying,sizing and then paving it in the pavement machine.Preheating temperature reaches the set value of 200?,setting the side pressure distance 50 mm.Starting the load operation,the first stage of the pressurized area.hot pressing pressure is set at 30 MPa,the side pressure is 6MPa,For 4-5 minutes,high pressure shaping;product into the pressurized area 2,2 zone pressure set 25 MPa,regulator heat transfer,duration 20 minutes;3 area set pressure of 20 MPa,duration 4-5 minutes;ending.(3)In better continuous hot pressing process produce reconsolidated square lumber,its mechanical properties are: when the disigned density is 0.65g/cm3,us PF as the adhesiveand resin content is 15%,the deflection modulus of elasticity is 5147.48 MPa,the flexural strength is 43.39 MPa,the longitudinal compressive strength is 33.77 MPa.the above hot pressing process measured mechanical properties: the use of phenolic resin adhesive,the amount of sizing,density 0.65 g / cm3,bending elastic modulus of,bending strength of,along The compressive strength was s;formaldehyde resin adhesive was used,the amount of sizing was 15%,the amount of ammonium chloride was 1.5%,the flexural modulus was4429.19 MPa,the flexural strength was 37.98 MPa,the compressive strength was 30.64 MPa.(4)Through the weatherability test of reconsolidated square materials of cotton stalk and mulberry branch,with PF as adhesive,and density is 0.7g/cm3.The weight loss rate of respectively reconsolidated square materials of cotton stalk and mulberry branch were2.36% and 2.24% When the density is 0.8g/cm3,the weight loss rate of reconsolidated square materials of cotton stalk and mulberry branch were 2.47% and 2.45%.use MDI as adhesive,density is 0.7g/cm3(MDI),the weight loss rate of reconsolidated square materials of cotton stalk and mulberry branch were 2.47% and 2.45% respectively.When the density is 0.8g/cm3,the weight loss rate of reconsolidated square materials of cotton stalk and mulberry branch were 2.82% and 2.60% respectively.When the type of adhesies and materials are the same,the large the density,the smaller the weight loss rate of weatherability.The weight loss rate of reconsolidated square materials of cotton stalk was slightly larger than reconsolidated square materials of mulberry branch.(5)After the weathering test,as thetest time increased,the two kinds of reconsolidated square lumbers' Hunter whiteness decreased,and the variation range was small,and there were no significant difference between the two kinds of reconsolidated square lumbers.The two kinds of MDI reconsolidated square materials of cotton stalk and mulberry branch were slightly discoloration or very slight discoloration,PF reconsolidated square materials of cotton stalk and mulberry branchs' color change is small,belong to very slight discoloration.Overall,the two kinds of reconsolidated square lumbers' color change are little change,belong to slight discoloration or a slight degree of discoloration.(6)The internal bonding strength of the two groups of recombinant materials was the same,the internal bond strength decreased with the increase of time under the same adhesive,and decreased significantly from 160 hours to the end of the experiment,The decline tends to be flat.The internal binding strength of the two kinds of straws decreased was 29.58-60.36%,which was slightly better than that of recombinant bamboo(45-66%).the swelling rate of the two kinds of recycled materials was higher than that in the first two days Were greater than those of the reconstructed bamboo.(7)Through the mid-infrared detection,according to the infrared spectrum of the two kinds of recombinant materials,the main chemical composition analysis that,main chemical composition of the main components of cellulose,hemicellulose and polysaccharides,monosaccharides reduced.