Uncaria gambier tannin adhesives for exterior grade plywood

摘要

Resins were prepared from phenol formaldehyde and Uncaria gambier tannin by copolymerization at 100°C.Tannin was used to substitute phenol upto 50% using 5,8and 11% alkali concentrations.Adhesive formulations and gluing conditions were examined by preparing laboratory 3-ply sal(Shorea robusta)boards(53.34cm x 53.34cm).In order to study the effect of alkali concentration and molar ratio of phenol with tannin,the gluing results obtained were analyzed and it was revealed that the glue shear strength of the plywood can meet the requirements of the Indian Standards IS:303-1989,for exterior grade plywood.Hence Uncaria gambier tannin would be a desirable substitute for phenol as a low cost material and the studied tannin based adhesive is suitable for industrial application.