Performance of protein-based wood bioadhesives and development of small-scale test method for characterizing properties of adhesive-bonded wood specimens

A small-scale test method to measure the tensile strength of adhesive-bonded wood strip specimens was developed by simple modification of commercially available binder clips. As bioadhesives, soy protein concentrate (SPC) and gelatin resins were prepared and were evaluated for shear and tensile bond strengths of bamboo and maple wood-bonded specimens. Titebond-II (TB-II), a commercially available wood glue was also tested to compare its bonding property to SPC and gelatin-based bioadhesives. TB-II glue showed the highest shear and tensile bond strengths with both bamboo and maple wood strips. Hot-pressing increased the shear and tensile bond strengths of SPC resin with wood specimens by 500% while the increase for gelatin resins was up to 200%. Roughness profile and surface properties were also characterized with an optical interferometric profiler and a scanning electron microscope. The results indicated that rougher surface significantly increased the bond strengths in both shear and tensile modes.