Study On Chemical Crosslinking And Polysaccharide Modification Of Soy Protein-based Adhesive

To strength the toughness and water resistance of soybean meal-based adhesive,soybean meal as raw material was used to prepare an adhesive using the long-chain cross-linker diethylene glycol diglycidyl ether(DGDE)and the denaturation agent sodium dodecyl sulfate(SDS).The mechanical properties and structural characteristics were investigated to study the effect of DGDE and high pressure homogenization on the properties of the resultant adhesives.Meanwhile,to investigate the effect of soybean polysaccharide on the performance of the adhesive,sodium hexametaphosphate was used to cross-link soybean polysaccharide,and then the mixture of cross-linked soybean polysaccharide and SPI was used to produce a soybean meal-based adhesive.The effects of polysaccharide on the properties of adhesives were characterized using Fourier-transform infrared,thermogravimetric analysis and scanning electron microscope.The main conclusions were listed:1.The long-chain cross-linker DGDE could strength the toughness and water resistance of the result adhesive.Because chemical reactions between epoxy groups of DGDE and active groups of protein molecules formed a cross-linking structure,the water resistance of the adhesive was significantly increased.Meanwhile,DGDE was a long-chain cross-linking agent,strengthening the toughness of cured adhesive and reducing the brittle of the adhesive layer,when added 8 wt%DGDE,the wet shear strength was increased by 181.08%and reached 1.04 MPa.2.Homogenizing treatment with DGDE modification could significantly improve the water resistance of adhesive.The unfolded protein molecules rearranged during high-pressure process and exposed additional hydrophobic and polar groups,increasing the solubility and dispersion of protein,which made the adhesive more uniform and stable.Modification soy protein adhesive was broken using high-pressure homogenizer under 40 MPa for 10 minutes,and the wet shear strength was increased from 0.31 MPa to 1.05 MPa,by 238.71%.3.The cross-linking of polysaccharide could reduce the viscosity of protein-based adhesive and improve the boding strength of the adhesive.The soybean polysaccharide was cross-linked to use green cross-linker sodium hexametaphosphate.Next,CL-SSPS was used to conjugate soy protein to produce a soy protein adhesive,when adding 4.5 wt%SHMP,the viscosity of adhesive was reduced to 14138 mPa s,and the bond strength of the three-plywood was increased by 90.38%,reaching 0.99 MPa.