The Effects Of Ulastronic/high Pressure Homogenization On The Performance Of Soybean Meal-based Adhesive

In order to solve the problem of soybean meal-based adhesive,which owns large particle size,poor solubility and low uneven distribution,resulting in appearance of weak boundary layers and poor water resistance.In this study,soybean meal as raw material,treated by ultrasonic and high pressure homogenization respectively,was mixed with TGA to prepare an adhesive.The size distribution,residual rate,thermal stability,functional groups and fracture surface of resultant adhesive were characterized.The wet shear strength of plywood bonded by resultant adhesives were tested.The different time of ultrasonic,the different time and pressure of homogenization were utilized to investigate the effect of performance of resultant adhesives.The main conclusions were listed:1.Along with increasing the time of ultrasonic,the particle size of soybean meal decreased.The particle of untreated soybean meal ranged from 85.6 to 119.4?m,and the particle of treated soybean meal ranged from 16.6 to 29.0?m.The soy proteins were denatured through the ultrasonic,exposing a lot of hydrophilic groups,which were reacted with TGA to form a lot of ester bonds,resulting in improving crosslinking density,leading to enhance the water resistance.After ultrasonic,thermal stability of cured adhesive was increased and fracture surface,owning little holes and cracks,became smooth,which is advantage to avoid the invasion of water,which made the water resistance improve constantly.The wet shear strength of plywood was increased and then decreased with increasing the time of ultrasonic.The residual rate was increased by 15.8%,the wet shear strength was 1.03 MPa,increased by 368.2%compared with the wet shear strength of plywood bonded by untreated adhesive,and the moisture uptake rate of various soy proteins was deereased by 22.3%through a 20-minute treatment.2.As the time of homogenization increased,the particle size of soybean meal decreased.The particle of untreated soybean meal ranged from gl.6 to 134.4?m,and the particle of treated soybean meal ranged from 13.9 to 27.3?m.The molecule chains of soy protein were unfolded,exposing a lot of hydrophilic groups.The number of hydrophilic groups was increased with increasing the time of homogenization.Under 20 MPa for 7 minutes,the moisture uptake rate of various soy proteins was increased by 54.9%,which were reacted with TGA to form a crosslinking network structure.The residual rate was increased by 14.0%,leading to form a denser structure.After homogenization,thermal stability of cured adhesive was increased and fracture surface with less holes and cracks,became smooth,leading to the further increase of water resistance.The wet shear strength reach 1.03 MPa,increased by 368.2%compared with the wet shear strength of plywood bonded by untreated adhesive.3.As the pressure of homogenization increased,the particle size of soybean meal decreased because soybean meal particles were crashed.The particle of untreated soybean meal ranged from 80.7 to 138.3?m,and the particle of treated soybean meal ranged from 15.6 to 25.4?m.Under 20 MPa for 5 minutes,the moisture uptake rate increased to 5.47%,increased by 54.9%compared with untreated soy proteins.And the residual rate arrived 81.6%,increased by 14.0%compared with untreated soybean meal-based adhesive.The wet shear strength reach 1.01 MPa,increased by 215.6%compared with the wet shear strength of plywood bonded by untreated adhesive.When the pressure increased to 80MPa,the particle size increased due to the re-aggregation of small molecules.The hydrophobic area became larger.The moisture uptake rate decreased by 9.7%,resulting in the decrease of reactivity.The wet shear strength decreased by 26.7%compared with the plywood bonded with resultant adhesive which was prepared under 20 MPa for 5 minutes.