Evaluation of glycolaldehyde as a formaldehyde substitute in urea-based wood adhesives

Glycolaldehyde, produced from cracking of glucose, was tested as a substitute for formaldehyde in urea-based wood adhesives. Initially, different parameters (water content, aldehyde/urea-ratio, curing temperature, and time) were screened to identify the optimal curing conditions providing the highest bond strength. Afterwards, the system was reformulated as a 2-component system and compared to a urea-formaldehyde 2-component system, which showed a comparatively low strength of the resulting resin. Different hardeners were tested, and AlCl3 showed an 80% increase in bond strength for the resin compared to NH4Cl. Infrared and nuclear magnetic resonance analyses were performed to ensure formation of the desired aminal bond network, which showed that the hardener was essential for proper curing of the resin. Finally, a urea-glycolaldehyde-formaldehyde resin was tested that further indicated major differences between the reactivity of formaldehyde and glycolaldehyde.