Effects of urea on freeze-thaw stability of starch-based wood adhesive.

Urea was used to improve the freeze-thaw (F/T) stability of a renewable starch-based wood adhesive (SWA). The improved stability was supported by the enhanced viscosity stability and bonding performance stability after repeated F/T cycling. The results of dynamic time sweep experiments, differential scanning calorimetry (DSC) and pulsed nuclear magnetic resonance (PNMR) showed that the improved stability can be due to the ability of urea to inhibit the retrogradation of starch molecules in the starch-based wood adhesive system. Urea can be used as an effective additive for improving storage properties of starch-based wood adhesive in low temperature environment. Approximately 15% (w/w) urea was the determined optimal dosage.