Influence of N,N-dimethylformamide on one-component moisture-curing polyurethane wood adhesives

The influence of the solvent N,N-dimethylformamide (DMF) on one-component moisture-curing polyurethane (1C-PUR) bonded wooden specimens was investigated. The applied methods were ATR-IR spectroscopy, VIS-NIR spectroscopy, FT-IR microscopy, UV Fluorescence microscopy, Nanoindentation, and AFM imaging. Findings reveal that DMF influences the curing kinetics of the 1C-PUR, supporting its thorough conversion by affecting the morphology and mechanical properties of the cured adhesive. Furthermore, DMF partially dissolves the wood׳s lignin and seems to make bound wood moisture more available for reaction with the adhesive. The outcomes confirm that 1C-PUR enters neither the wood cell walls nor the wood rays. The vessel system of the early wood represents the major pathway for the penetration of 1C-PUR into the beech wood.