Preparation and properties of inorganic filler modified wheat protein/tannin composite adhesive
Formaldehyde-free bio-based wood adhesive was prepared by using wheat protein(WG)and condensed tannin(CTs)as raw materials.Using montmorillonite,kaolin,heavy calcium carbonate,light calcium carbonate and hydroxyapatite as fillers for modification,the filler-modified composite adhesive was prepared by the blending method.The influence of inorganic filler type on the properties of WG/CTs composite adhesive was investigated,and water-resistance bonding strength,scanning electron microscopy(SEM),thermogravimetric analysis,insolubility in boiling water,viscosity and other tests were analyzed.The research results showed that after adding fillers,the viscosity of WG/CTs composite adhesive increased to varying degrees,and the thermal stability of adhesive was also improved compared to the control group adhesive.There were significant differences in the water resistance of adhesive modified with different inorganic fillers,but the wet strength of plywood all exceeded 0.7 MPa,meeting the requirements of the national standard of Class Ⅱ plywood.The test results of insolubility in boiling water showed that light calcium carbonate improved the water resistance of adhesive.SEM images and crack assessment of adhesive layer showed that heavy calcium carbonate and light calcium carbonate had good compatibility with the adhesive,indicating that calcium carbonate filler had no effect on the toughness of adhesive layer and was a good filler choice.
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