Preparation and properties of a modified corn flour-lignin-glyoxal as a Green wood adhesive

A corn flour- lignin-glyoxal (CLG) green wood adhesive was prepared by esterification and polyisocyanate prepolymer crosslinking of corn flour. At first corn flour was esterified by maleic anhydride and 10% polyisocyanate was added to it. The modified corn flour was then added at various contents (2, 4 and 6% on resin solids) to phenolated lignin and glyoxal solution to obtain the CLG resin. According to the FTIR spectra, the ester groups (-C=O) at 1730 cm-1 increased due to the esterification of corn flour by maleic anhydride. The addition of the modified corn flour significantly increased the viscosity and solid content and accelerated the gelation time of CLG resins. DSC analysis indicated that increasing the modified corn flour continuously decreases the gel onset and curing temperatures of the resin. Greater mechanical strength and higher dimensional stability of panels bonded with CLG resins can be obtained by modification of corn flour.