Effect And Mechanism Of Enhancement And Anti-microbial For Soy Protein Based Adhesives And Adhesive Films

Pure soy protein based adhesives exist some defects,such as be vulnerable to wet,microbial attack and low bonding strength.Additionally,concerns such as poor bonding strength,brittleness,cracking,impact and aging intolerance may occur in glue line of plywood,which would limit its applications.It is of significant theoretical and practical significance to find out influence factors and modification measures.This work identified the main harmful microorganism,respectively screened a preservative and enhancer and worked on the mechanisms.This research also prepared a film as the simplified model for adhesives and optimized the process parameters.Additionally,chitosan was added into the film to enhance some properties and its feasibility in plywood was also discussed.The main spoilage microorganisms in freshly prepared adhesives were considered to be Bacillus amyloliquefaciens,Bacillus cereus or Bacillus thuringiensis.Those that attacked the cured adhesives belonged to be Aspergillus fungi.The degree of microbial attack was alleviated and the start time was delayed because of introducing p-cumylphenol.The growth of microorganism was inhibited inside the adhesive.Phenolic hydroxyl groups in p-cumylphenol have antimicrobial effect.Microorganisms grown on the adhesive surface were also controlled when adding p-cumylphenol at a range of 1.5wt%to 2.0wt%.Noticeably the bonding strength increased 26.75%after more high purity p-cumylphenol was used during high humidity treatment for 28 days.Water resistance,bonding strength and some other properties can be improved by incorporating silicone-acrylate emulsion into adhesives.Interpenetrating polymer networks with rigidity and toughness were formed among three components.Bonding strength was increased by 41%,85.9%and 90.5%when 15wt%of emulsion was added at three test conditions.Internal structure,thermal stability and antimicrobial effect were improved.Solid content increased by 11.56%while viscosity reduced by 61.32%.Dosage of glycerol had considerable effect on the mechanical property of alkaline soy protein based film among four experimental factors.When the weight vector of tensile strength and elongation was 0.5:0.5 in fuzzy synthetic discrimination,the optimal process parameters of the mass concentration of soy protein solution,dosage of glycerol,synthesis temperature and pH value were 4%,20%,65℃ and 10 respectively.Tensile strength and elongation reached 5.41MPa and 186.36%under this process.Chitosan and soy protein isolate were well compatible at the molecular level and hydrogen bonds were formed between them.In blend films,tensile strength increased by 450%while elongation at break reduced by 17%.Antimicrobial effect was improved and no distinct differences were observed in the microstructure.In blend adhesives,bonding strength was increased by 34.2%and antimicrobial effect was also improved.