Study On Soybean Protein Adhesive Modified By ATRP Method

The bonding strength of traditional unmodified soybean protein adhesives comes from intermolecular forces such as hydrogen bonds formed between protein molecules and with wood,and is greatly affected by moisture,resulting in poor water-resistant bonding strength of bonded products,and the prepared glue has poor permeability,so that it cannot form an effective"glue nail"with the board.In this paper,soybean protein was pretreated to open the higher-order structure of the protein and expose more reactive groups.The Atom Transfer Radical Polymerization（ATRP）method was used to controllably graft glycidyl methacrylate（GMA）to SPI.On the protein molecule,improve the cohesion and toughness of the adhesive;in the early stage,a milder ionic liquid was used as a pretreatment solvent to partially destroy the high-level structure of the protein,and in the later stage,the controllable grafting of GMA by the ATRP method was used to ensure the viscosity of the prepared adhesive to improve the coating performance and penetration performance of the adhesive;N-methylol acrylamide（NMA）was introduced between the soybean protein adhesive and poplar veneer to increase the number of plywood prepared The bonding strength was improved,and the effect of improved the wood breakage rate.（1）GMA was grafted onto soybean protein molecules by ATRP method in ionic liquid（[BDMIM][Cl]）to prepare SPI copolymer.The results of infrared spectroscopy,H NMR and EDS showed that 2-bromoisobutylated SPI was successfully prepared,which provided an active reaction site for the later ATRP reaction.The analysis of infrared spectroscopy,H-NMR spectroscopy and thermal analysis showed that the soybean protein graft copolymer was successfully synthesized.The solid content of the prepared adhesive was 23.9%,the viscosity was 684 MPa·s,and the GMA was 140m L,Cu Br was 147.2 mg and the oil bath time was 3 h,the bonding strength was 1.44MPa,which meet the requirements of the national standard GB/T 9846-2015 for Class II plywood.（2）SPI was liquefied by adding 1.0 wt%lithium salt（Li Cl,Li Br,Li Ac）ionic liquid as solvent system.The results of single factor experiment showed that the optimal pretreatment method was 1 mg/m L.The ionic liquid and 1%mass concentration of lithium chloride solution were magnetically stirred at 50°C for 3 h to liquefy the SPI.Then carry out"semi-homogeneous"graft copolymerization by ATRP method to obtain SPI-g-PGMA graft copolymer.The dissolution mechanism of 1-butyl-2,3-dimethylimidazolium chloride was proved and analyzed in detail by the determination of infrared spectrum,hydrogen NMR spectrum,heat treatment and scanning electron microscope:Cl^-in 1-butyl-2,3-dimethylimidazolium chloride will form hydrogen bonds with soybean protein,destroy the original tissue hydrogen bonds.（3）The poplar veneer was pretreated with NMA.The results showed that the penetration depth of the poplar veneer treated with 8%mass concentration of NMA at room temperature could reach 0.64 mm,compared with the untreated one.The penetration depth of poplar veneer increased by 0.45 mm;the water contact angle increased from 66.0°to 136.9°.In addition,the best treatment method is to treat poplar veneer with 8%mass concentration of NMA at room temperature.The effect of hot pressing process on the bonding strength and wood failure rate of plywood was obtained by response surface analysis.The research results showed that the optimal hot-pressing process is as follows:the amount of glue applied on one side is 180 g/m~2,the hot-pressing temperature was 120℃,and the hot-pressing time is 40 s/mm.And through the analysis of the micro-morphology of the bonding interface between poplar veneer and plywood,the influence mechanism of NMA on the structure of poplar veneer was analyzed,and the structure-effect relationship between the change at the glued interface and the increase of plywood wood failure rate was clarified.Synergistic effect of gluing properties.