| In this thesis it has been researched that the different condition of enzyme treatment had the influence on the property of wheat-straw fiber with wheat-straw fiber and enzyme as test materials, and the optimum technology has also been studied. Otherwise, the mechanism of bonding performance has been revealed about the wheat-straw fiber treated by enzyme, and the properties of wheat-straw fiberboard has been investigated, and the dimensional stability and sorption have been analyzed in detail. Moreover, the poplar micro/nanofibrils has been made by synergistic treatment of ultrasonic and cellulose, and their properties have been tested, and the technology has been discussed by adding poplar micro/nanofibrils into UF to reform the gluing property of wheat-straw fiberboard. The conclusions were listed as following: he gluing property of wheat-straw fiberboard. The conclusions were listed as following:1) The optimum conditions of xylanase treatment were treatment temperature 45℃, treatment time4h, pH value4.5, enzyme usage 205.0IU·g-1 through studying the influence of xylanase treatment condition on the property of wheat-straw fiber.2) The surface contact angle, surface functional group,chemical components and microstructure of wheat-straw fiber were studied with surface tention and contact angle measure instrument, fourier transform infrared spectroscopy(FTIR) and scanning electricity microscope(SEM).That results indicated that the surface contact angle of xylanase-treated wheat-straw fiber was decreasing evidently and reached to 50°.The FTIR spectra of treated wheat-straw fiber showed that the xylanase could remove parts of simple carbohydrate and lipophilic extractives, at the same time,cellulose and lignin were activated with–OH increasing,the content of ash, cold-water extractive, hot-water extractive and benzene-alcohol extractive decreased.The SEM showed that the surface of treated wheat-straw fiber was rough, the wax-layer and hemicellulose of treated wheat-straw fiber were dissolved. The differential scanning calorimetry (DSC) study revealed that the compound of UF and xylanase-treated wheat-straw fiber exhibited an obvious release peak appeared on 107.656℃, this indicated the curing reaction of UF happened, and the temperature approximated to curing temperature of unitary UF.3) Compared with fiberboard making from untreated wheat-straw fiber, the internal bonding strength (IB), test tensile strength, thickness swelling rate of water absorption for 24h (24hTS), storage modulus and loss modulus of wheat-straw fiberboard were improved obviously after xylanase pretreatment of wheat-straw fiber. The IB and test tensile strength increased from 0.34MPa to 0.67MPa, and 7.78MPa to 14.15MPa, respectively.The 24hTS decreased from 36.45% to 18.40%.4) The dimensional stability on the length direction, width direction and thickness direction,which xylanase-treated wheat-straw fiberboard were better than the reference samples.The sorption isotherms of wheat-straw fiberboard presented"s"shape, which was similar to sorption isotherm of wood,wood-based composite and rich-straw particleboard.The equilibrium moisture content of adsorption and desorption,the xylanase-treated fiberboard′s was lower than xylanase-untreated fiberboard′s under the identical environmental temperature and relative humidity condition.The experiment data could be well modeled by GAB mathematical equation.5) The poplar micro/nanofibrils could be prepared with synergistic treatment of ultrasonic and cellulase, and their diameter distribution ranged from 50nm to 1μm. The IB of wheat-straw fiberboard reached to 0.86 MPa by adding appropriate poplar micro/nanofibril suspension into UF. (50 Figures; 17 Tables)...
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