Adhesion interaction of one-component polyurethane in cross-laminating southern pine wood treated with micronized copper azole—type C (MCA-C)

Compatibility between preservative and resin plays an important role in determining the adhesive performance of preservative-treated engineered wood products. This study aims to elucidate the interactions between micronized copper azole—type C (MCA-C) treated southern pine (Pinus spp.) at two retention levels and one-component polyurethane resin (PU). The surface wettability of both untreated and treated wood was examined using a dynamic water contact angle and it was found that water wettability of the latewood at high retention level treatment was significantly higher than those of untreated and at low retention level. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy analysis of wood and resin samples indicates that neither interaction between MCA-C and wood nor unique peaks for wood/resin mixture were detected. Curing behavior of PU resin and wood by differential scanning calorimetry (DSC) analysis shows that preservative treatment dramatically retarded the curing of the PU resin with the low retention treatment being the most difficult to cure with. The bond-line thickness and depth of resin penetration measurement by confocal laser scanning microscopy (CLSM) indicates that MCA-C treatment on wood significantly affects the bond-line thickness and the penetration of PU resin. In particular, bond-line thickness significantly decreased while glue penetration significantly increased as treatment retention increased. Although the low retention treatment is the most difficult to cure with PU resin, the bond-line thickness and resin penetration depth in wood structure could also affect the final bonding performance of the engineered wood.