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• Repeatable and damp-heat resistant bamboo-strip scarf joints were prepared. • The rapid (within 8 s) lengthening technique of scarf jointed BS was realized. • The maximum tensile strength of scarf joints prepared with TPU was 197.9 MPa. • TPU film showed the best performance in repeatability and damp-heat resistant. • The results provided support for continuous manufacturing of bamboo composites. Bamboo, which has excellent mechanical strength, is an ideal raw material for manufacturing high-performance bio-composites. However, due to a lack of fast, high-strength lengthening technology for bamboo units, the large-scale, mechanized, continuous production of bamboo woven materials has not been fully developed. In this work, bamboo strips (BS) with 0.5 mm thickness were used as a basic unit to prepare lengthened bamboo strips with the scarf jointing method. The effects of scarf jointed angles and hot-melt adhesive type on the scarf bonding performance were systematically investigated. The tensile strength of BS scarf joints appears to increase as the scarf joint angle decrease. Scarf joints prepared with low-cost thermoplastic polyurethane (TPU) film outperform those prepared with reactive polyurethane (PUR) or ethylene vinyl acetate copolymer (EVA) hot-melt adhesives in terms of maximum tensile strength (197.9 MPa), secondary repeated bonding performance, and damp-heat aging resistance, where tensile strength of 136 MPa was retained after a 120 h cycle aging test. Specimens bonded with PUR adhesive are resistant to damp-heat aging, but show unsatisfactory secondary repeated bonding performance. The tensile strength and damp-heat aging resistance of EVA bonded specimens are unacceptable due to an unreliable bonding interface. We developed a facile solution for high-strength BS lengthening with repeated bonding and damp-heat resistant characteristics, which may provide technical support for the large-scale, mechanized manufacturing of bamboo-based composites. [ABSTRACT FROM AUTHOR]

Waste particleboard is a valuable feedstock for the particleboards. Recycling waste panels into particleboard is hindered by adhesive residues in the particles. This study aims to investigate the effect of adhesive residues on the physical and mechanical properties of particleboard. The chemical properties and wettability of particles containing pMDI and UF residues were investigated, and these particles were further used to produce particleboards. Results revealed that the pMDI residue is incompatible with fresh UF resin and forms weak bonding in the particleboards. However, the pMDI residue can continue to react with the fresh pMDI and form strong adhesion. The UF residue cannot cross-linked with the fresh UF, and the additional hydrophilic groups, resulting in a severe reduction in the dimensional stability of the panels, but the decrease in the mechanical properties is not significant. Interestingly, the UF residue promotes the curing of fresh pMDI, thus benefiting the mechanical properties of the panels. This study can guide the selection of adhesives in producing recycled particleboard using waste particleboard, thereby promoting the efficient recycling of waste particleboard. • The interactions between residual and fresh adhesives were analyzed. • The pMDI residue is incompatible with fresh UF resin. • Both pMDI and UF residues can react with fresh pMDI to promote its curing. [ABSTRACT FROM AUTHOR]