Effect of the ACQ Preservative on the Bonding Strength of Aqueous Polymer Isocyanate Bonded Masson Pine Joints and on the Adhesive Penetration into Wood

The influence of alkaline copper quaternary (ACQ) preservative was studied relative to the bonding strength of Masson pine joints and the penetration of the adhesive into wood. Masson pine specimens treated with ACQ of three concentrations (0.1%, 0.5%, 1.0%) were bonded with aqueous polymer isocyanate (API) adhesive, and the shear strength, wood failure percentage, bondline thickness, average penetration depth (AP), and effective penetration depth (EP) of the wood joints were evaluated. The shear strength (6.34 to 6.85 MPa) and the wood failure percentage (87.0% to 87.8%) of the three series of treated joints were significantly lower than that of the untreated samples, while the treated specimens showed significantly larger bondline thickness (43.3 to 47.2 μm), smaller AP (30.6 to 35.8 μm), and smaller EP (24.7 to 25.7 μm) than the untreated specimens. The increase of ACQ concentration from 0.1% to 1.0% had no significant impact on the bonding strength and adhesive penetration parameters. The correlation between shear strength and penetration depths of treated joints was significant at the 0.01 level based on Pearson correlation analysis, while the coefficient of determination (R2) of the shear strength resulted from least squares regression analysis was 0.250 and 0.143 for AP and EP, respectively.