Study On Preparation And Properties Of Soybean Protein Adhesive Modified By Epoxide

This thesis is mainly divided into three parts:Alkaline protease was used to modify soybean protein adhesive,and ethylene glycol diglycidyl ether triethylenetetramine epoxide（EETA）was synthesized.We mainly investigated the effects of the amount of alkaline protease added,hydrolysis temperature,p H,and hydrolysis time on the dry and wet bonding strength of adhesives;The synthesis of ethylene glycol diglycidyl ether triethylenetetramine epoxide,and the effects of the amount of EETA,the molar ratio of ethylene glycol diglycidyl ether（EGDE）to triethylenetetramine（TETA）,temperature,p H,and time on the dry and wet bond strength of the modified adhesive were investigated;Explore the optimization of hot pressing process conditions for EETA modified adhesive.The research results are as follows:（1）Alkaline protease modified soybean protein adhesiveThe results of single factor and orthogonal experiments showed that the addition amount of alkaline protease was 10000 U·g^-1.At p H 9.5,the temperature of enzymolysis was 60℃,and the enzymolysis time was 100 min,at this time,the viscosity significantly decreased to 14 s,which was convenient for the coating and sizing of adhesive,and better opened the spherical structure of protein,exposing more hydrophobic groups and active site.The dry bonding strength of enzyme modified adhesive is 1.47 MPa,which is 32.43%higher than the unmodified soybean protein adhesive（0.74 MPa）.Its wet bonding strength is 0.48 MPa,which is slightly higher than the unmodified soybean protein adhesive（0.28MPa）.However,it is far lower than the strength standard for plywood（≥0.7 MPa,GB/T9846-2015）.Therefore,hydrophobic epoxy substances were added in subsequent experiments to utilize the large amount of amino groups in soybean protein The carboxyl group and active site react with the epoxy group to improve the water resistance of the adhesive.（2）EETA modified soybean protein adhesiveThe ethylene glycol diglycidyl ether triethylenetetramine epoxide（EETA）with multiple epoxy groups and flexible long chains was prepared by ring opening reaction of the amino epoxy group of ethylene glycol diglycidyl ether（EGDE）and triethylenetetramine（TETA）without solvent and catalyst,Exploring the optimal preparation scheme of EETA modified soybean protein adhesive through single factor and orthogonal experiments,and characterizing and testing its structure,properties,and bonding performance.The experimental results showed that the optimal preparation conditions for modified soybean protein adhesive were EETA dosage of 12g,p H of 10,reaction time of 30 minutes,molar ratio of ethylene glycol diglycidyl ether to triethylenetetramine of 18:1,reaction temperature of 60℃.At this time,the dry and wet bonding strength of the adhesive reached 1.75 MPa/0.98 MPa,far exceeding the national standard for Class II plywood adhesive requirements（≥0.7 MPa）.According to the analysis of variance results,The dosage of EETA has a significant impact on the bonding performance,and the storage period of modified soybean protein adhesive has been extended from 3 days to 120 days.（3）Optimization of Hot Pressing Process for EETA Modified Soybean Protein AdhesiveExploring the hot pressing process of EETA modified soybean protein adhesive,investigating the effects of hot pressing temperature,hot pressing time,hot pressing pressure,and adhesive amount on the adhesive’s bonding performance through single factor experiments and orthogonal experiments.The results of orthogonal experiments and analysis of variance indicate that the hot pressing process for EETA modified soybean protein adhesive is determined as follows:the application amount is 260 g/m²,the hot pressing pressure is 3 MPa,the hot pressing temperature is 140℃,and the hot pressing time is 8 minutes.The dry and wet bonding strength of the plywood prepared under these conditions increased from 0.74 MPa and 0.28 MPa to 2.03 MPa and 1.11 MPa,respectively,an increase of 174%and 516%,far exceeding the national standard for type II plywood（≥0.7 MPa,GB/T9846-2015）.FT-IR,TG-DTG,XRD,and SEM characterization analysis of the above adhesives showed that the EETA modified soybean protein adhesive had a denser hydrophobic network structure and higher thermal stability,and significantly improved bonding strength and water resistance.During the exploration of the hot pressing process,there was no overflow or bubbling phenomenon,which played a positive role in the development of soybean protein adhesive for wood plywood.