Effects of the drying process on the shear strength and morphology of the bonding interface of laminated wood

To investigate the influence of the drying process on the bonding properties of laminated wood, a poplar veneer was impregnated with low molecular-weight phenol formaldehyde (PF) resin and laminated wood was created and studied. The effects of drying temperature, drying time and solid content of the PF resin on the moisture content (MC) of the impregnated veneer after drying and the shear strength of the laminated wood were analyzed with an orthogonal experiment. The microscopic mechanism of the bonding performance of the laminated woods was investigated by fluorescence microscopy. The experimental results showed that the higher the PF resin solid content was, the larger the weight gain percentage of the impregnated veneer was. In addition to drying temperature and drying time, the solid content of PF also had a significant influence on the MC of the impregnated veneer after drying. The shear strength of the laminated wood affected by the drying temperature, solid content of PF and drying time and the drying temperature had a more significant effect than the other two factors. The best drying process was a drying temperature of 50 °C, a drying time of 2 h, and a PF solid content of 30%. The fluorescence analysis showed that the shear strength of the laminated wood was affected by the intensity of the PF resin on the bonding interface, and the average and effective penetration depth of the PF resin in the veneer increased with the increase in the drying temperature.