Poplar Veneer Of Moist Heat Treatment On The Properties Of Laminated Veneer Lumber

The dissertation focused on the hygrothermal treatment of poplar veneer andprocessing poplar laminated veneer lumber so as to find out the effects of hygrothermaltreatment on veneer on the finished laminated veneer lumber products. The special andnovel contents are hygrothemal treatment on poplar veneer by introducing thetraditional method from hygrothermall modifying treatment of solid wood, which willpool a new way for making uniform plywood in thickness dimension.The adding moisture content of fir-drying veneer test showed that it was only20minutes to make the moisture content to water saturation, which about 50％. Theparameters of hygrothermal treatment for saturated poplar veneer are prescribed in L₉(3⁴)table with the factors, that is, temperature being 140℃, 150℃, 160℃; pressure being 1.0MPa, 1.5 MPa, 2.0MPa, treating time being 2min, 3min, 4min And the L₉(3⁴) tableresults were illustrated as followings:Compared to the common poplar veneer, density of treated veneer is enhanced38.7％, ranging in 0.49～0.55g/cm³. Function of treatment time, pressure for treatinghad obvious effect on the swelling ration of treated veneer in turn. After dipped in coldwater for 24hrs, the swelling ration in thickness of treated veneer is lower than that ofprevious air-drying veneer showing that a little plastic deformation happened.Optimizing factor level for hygrothermal treatment in this experience arefollowings: temperature,150℃; pressure2.0MPa; treating time,4min.Comparing testing of laminated veneer lumber made of treated veneer to commonLVL illustrated that treated veneer has special effect on increasing the whole propertiesof LVL such as horizontal shear, MOR. And the cross density grads can be declined byusing treated veneer. Horizontal shear has been increased more than 30％,accompanying with MOR going up 17.8％and swelling thickness being down 10％.