Development of new natural polymer-based wood adhesives III: Effects of glucose addition on properties of chitosan

The effects of a Maillard reaction between glucose and chitosan on the resultant chitosan films and the bonding properties of chitosans with different molecular weights were investigated. In film preparation, chitosan and glucose were dissolved in 1% acetic acid and dried in a Petri dish at 50°C. The bonding properties of the Maillard-reacted chitosan in three-ply plywood were evaluated by a tensile shear test. The weight, color, free amino groups, insoluble fraction, and thermal properties of the film changed significantly as the amount of added glucose increased. However, few differences in these properties due to the use of chitosan of different molecular weights were observed. The effect of glucose addition on the tensile strength of the film differed for chitosans of different molecular weights. Improvement of the strength by 10 wt% glucose addition was observed in low-molecular-weight chitosans. The dry- and wet-bond strengths were significantly enhanced with increasing glucose addition for low-molecular-weight chitosans. In addition, good bond strength was maintained even in 1% acetic acid solution. It was thus clarified that the bonding properties of low-molecular-weight chitosan were improved markedly by the environmentally safe method of glucose addition. © 2010 The Japan Wood Research Society.