Study On Preparation And Performance Of Water-resistant And Mildew-proof Composite Protein-based Adhesive

Soy protein-based adhesives has the advantages of a wide range of raw materials,degradable,and environmental friendly.However,its application in actual production is limited due to its poor waterresistant bonding strength,hard and brittle adhesive layer,and poor mold resistance.In the study,soybean meal is used as raw material,1,6-hexane dioldiglycidyl ether(HDE)is used as cross-linking agent,silk,blood meal and metal ions are used to synergistically strengthen and toughen soy protein-based adhesives,and research the effects of different proteins and metal ions on the water resistance,bonding strength,adhesive layer toughness,thermal stability and mold resistance of soy protein-based adhesives.SEM,XRD,FTIR,TG,DSC analysis and mechanical performance testing were used to analyze the micro morphology,structure,functional groups,thermal behavior and bonding properties of the adhesive and elucidated the mechanism of silk protein,blood protein and metal ions synergistically enhancing soy protein-based adhesive.The main conclusions are summarized as follows:(1)Silk fibroin had good compatibility with soy protein,and the strength and toughness of soy protein-based film modified by silk fibroin solution were significantly improved.The results showed that a physical crosslinking network was formed through the electrostatic interaction and hydrogen bonding between silk protein and PEI.Meanwhile,the excellent mechanical properties of silk played a key role in strengthening the protein film.The tensile strength of the silk fibroin modified protein film was 16 MPa,which was 136% higher than that of the control group.In the protein film modified by silk fibroin and calcium ion,due to the metal coordination between calcium ions and protein,the cross-linking density of the system was increased,which significantly improved the toughness of the film,and the maximum tensile strain reached 158%.(2)Silk fiber had excellent reinforcing effects on soy protein-based adhesives.Scanning electron microscopy showed that there was a good interface bonding between silk fiber and soy protein.As a reinforcing phase,silk fiber can effectively transfer stress,and the strong mechanical interlock between fibers and matrix improved the bonding performance of the adhesive.The water-resistant bonding strength of the plywood prepared by adding 2.5% silk fiber was up to 1.16 MPa,which was 52.6% higher than that of the control group,and the thermal stability of the adhesive was also significantly improved.(3)Soy protein-based adhesives modified by blood meal and metal ions synergistically had excellent bonding strength and mildew resistance.The soluble part of the blood meal provided active sites for chemical cross-linking and metal coordination,while the insoluble part had higher strength and dispersed stress.HDE,calcium ions and zinc ions were added to build multiple network structures,which endowed the soy protein-based adhesives better mechanical performance and mildew resistance.The water-resistant bonding strength of the prepared adhesive was increased from 0.48 MPa to 1.1 MPa,and the anti-mold action time was extended from 1 day to 14 days.In addition,the moisture absorption rate was decreased from 14.61 % to 11.86 %,the thermal stability was increased,and the cracks of the cured film were significantly reduced.