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The adhesive ability of bamboo scrimber is critical for its use in large‐scale engineering structures. Cold‐pressed bamboo scrimber with varying sanding mesh and density was made and then bonded with polyurethane resin. The adhesive was concentrated on the surface, assisting the anchoring into the material surface. The shear strength and immersion peel strength are studied as parameters to determine the glue qualities. The optimum gluing characteristics were obtained using a 120 grit sandpaper and a density of 1.15 g/cm3. The results indicated that at a density of 1.15 g/cm3, the gluing characteristics rose initially and subsequently dropped as the number of sanding meshes increased. The bonding strength improved with increasing density when 120‐mesh sanding was used. With increasing density, the bamboo fiber distribution inside the material got more compact, while the resin dispersion became more uniform. Thus, the surface porosity and roughness were decreased.

As a new type of green environmental protection material for outdoor use, the water resistance of bamboo scrimber composite (BSC) is crucial—the primary reason for a decrease in water resistance being bonding interface failure. From a bonding interface structure perspective, the influence mechanism of the resin content and density on the water resistance of BSCs remains unknown. Therefore, in this study, BSCs were prepared using Moso bamboo and phenol-formaldehyde resin, and the changes in the macroscopic and microscopic bonding interfaces before and after 28-h water-resistance tests were observed and analyzed. The results showed that the water resistance of the BSC increased with increasing resin content, with higher thickness swelling rates (TSRs) observed at higher densities. Obvious cracks were found at the macroscopic interface after 28-h tests, with higher resin contents leading to fewer and smaller cracks. With increasing density, the longitudinal fissures due to defibering process decreased, having an effect on width swelling rates (WSRs). Furthermore, porosity measurements revealed changes in the microscopic bonding interface; the difference in porosity before and after testing (D-value) showed the same trend as water resistance. Generally, we conclude that the macroscopic and microscopic bonding interface structures are closely related to BSC water resistance.

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