Effect of CMC formic acid solution on bonding performance of muf for interior grade glulam

This work aimed at determining the effect of adding a carboxymethyl cellulose (CMC) formic acid solution to melamine urea formaldehyde (MUF) on the bonding performance of the adhesive. The bonding performance, chemical structure and curing behavior of MUF adhesives with CMC (1%, 1.5% and 2.0% w/w) formic acid solutions were evaluated by the compressive shear test, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Considering practical timber construction projects, the effect of higher wood moisture content on the bonding strength of the adhesive was investigated. The compressive shear strength of MUF adhesives was nearly twice higher than required by BS EN 386 standard. The bonding strengths of the specimens at 18% moisture content (MC) were 7.18%, 4.8% and 4.95% lower than those at 12% MC with the addition of 1%, 1.5% and 2.0% (w/w) CMC contents, respectively. The bonding strengths of 12% and 18% MC blocks glued by the MUF adhesive containing 2% CMC reached 10.60 and 10.08 MPa, respectively.