Preparation and interfacial bonding mechanism of high-moisture-content bamboo strip-polyurethane composites

To address the high energy consumption and complex processing steps in conventional sliced bamboo production, this study developed an energy-efficient bonding strategy using PU adhesives for direct fabrication of high-moisture bamboo (HMB) composites, eliminating drying and softening pretreatments. Three PU adhesive systems were examined, among which the one-component moisture-curing polyurethane (1K-PUR) PU-1102 exhibited the most reliable bonding performance under wet conditions. The influences of adhesive spread rate and pressing pressure on interfacial strength and water resistance were systematically evaluated. Optimal bonding was achieved with a spread rate of 250 g/m2 and a pressing pressure of 0.5 MPa, resulting in strong interfacial adhesion and excellent resistance to delamination after cyclic water immersion. Spectroscopic analyses (FTIR and XPS) confirmed the formation of chemical linkages between isocyanate (-NCO) and hydroxyl/carboxyl (-OH/-COOH) groups, resulting in a dense, durable crosslinked interface. Overall, the findings demonstrate the feasibility of direct wet bonding using PU-1102 and provide a practical, scalable route for greener bamboo-based composite manufacturing.