Study On Properties And Mechanism Of Sepiolite And Nano-cellulose Enhanced Wood Adhesive

Fiber reinforcement is an important means to improve the mechanical properties of polymers.Therefore,in this thesis,fibrous materials such as sepiolite and nanocellulose were selected to modify UF resin adhesives,MUF resin adhesives,and soy protein adhesives.Based on the characterization of adhesive viscosity,solid content,functional group change,thermal stability,crystal structure,morphology,plywood bonding properties and formaldehyde emission to analyze the effect of sepiolite on the bonding strengyth and formaldehyde emission of UF?MUF resin,and the effect of sepiolite and nanocellulose on the adhesive properties of soy protein adhesives.The bonding,strengthening and toughening mechanisms of modified UF?MUF resin adhesives and soy protein adhesives are discussed.The main conclusions are as follows:1.Sepiolite scattered in the UF resin in the form of physical filling,is helpful for forming dense cured layer,improving the water resistance of adhesive.At last the bond streng,th of plywood increases by 39%to 1.1 MPa.2.The unique pore structure of sepiolite is beneficial to the release of formaldehyde from the plywood bonded by UF resin adhesive and MUF adhesive.3.The hydrogen bonding effect of silica hydroxyl on the surface of sepiolite and the active group on MUF resin chain makes the bonding strength of plywood increased by 27.8%to 1.15MPa.4.Sepiolite and nano cellulose exist in soybean protein adhesive matrix in the form of physical filling,which can transfer and disperse stress and reduce stress concentration,thereby reducing the damage of external force to the adhesive layer.At the same time,sepiolite and nanoscale cellulose can reduce the number of pores caused by moisture evaporation during adhesive curing process,making the adhesive layer more smooth and dense.Finally,the bonding strength of sepiolite and nanoscale prepared plywood reached 0.79MPa and 0.82MPa,respectively.5.The epoxy group on the surface of KH-560 modified sepiolite react with the active functional group on soybean protein molecular chain forming a crosslinked network structure,thus adding 2%modified sepiolite increase the the bond strength of plywood to 1.18 MPa.6.The epoxy group on the surface of KH-560 modified nanocellose react with the active functional group on soybean protein molecular chain forming a crosslinked network structure.At last the dry strength and wet strength of the modified adhesive were increased to 1.8 MPa and 1.08MPa respectively.7.Compound silane coupling agent modified sepiolite can toughen and strengthen soybean protein adhesive.The modifided sepiolite and soy protein molecular chains are linked by flexible long chain.The presence of sepiolite results in the formation of elastic network with long chain structure,which can buffer and effectively transfer external forces and improve the adhesion performance.Adding 1%of modifided sepiolite,the wet shear strength of plywood increased by 60%to 1.25MPa.