High‐Strength Bamboo Oriented Strand Board Fabricated via Different Pretreatments

ABSTRACT The mechanical performance of bamboo oriented strand board (BOSB) depends strongly on the interfacial bonding among the constituent bamboo strands and the adhesive matrix. Consequently, effective surface pretreatment strategies are essential for strengthening these interfacial interactions and fabricating high‐performance composites. This study systematically investigated the effects of five chemical pretreatments including γ‐aminopropyltriethoxysilane (KH550), 3‐glycidoxypropyltrimethoxysilane (KH560), sodium hydroxide (NaOH), branched polyethylenimine (PEI), and dopamine on the mechanical properties and interfacial reinforcement mechanisms of phenolic resin‐bonded BOSBs. Among the pretreatments examined, PEI produced the greatest improvement in flexural performance, whereas NaOH treatment resulted in the highest internal bond strength. Specifically, pretreatment with 2 wt% PEI increased the flexural strength, modulus of elasticity (MOE), and internal bonding (IB) strength to 266.33 MPa, 11.72 GPa, and 1.81 MPa, respectively, corresponding to increases of 131.9%, 74.0%, and 63.6% relative to those of the untreated control. Mechanistic analyses revealed distinct reinforcement pathways associated with the different pretreatments. PEI formed robust cross‐links between its amino groups and bamboo surface functional groups during hot pressing; NaOH etched surface waxes and partial hemicellulose of bamboo strand, increasing porosity and hydroxyl groups exposure and thereby facilitating resin penetration and mechanical interlocking. Meanwhile, dopamine self‐polymerized into a polydopamine (PDA) layer which could adhere to the bamboo surface via multiple noncovalent interactions and then undergoes secondary covalent cross‐linking with phenolic resin during hot pressing. Overall, this study elucidates the chemical‐bonding and mechanical‐interlocking mechanisms governing interfacial reinforcement, offering a theoretical foundation for the design and fabrication of sustainable, high‐performance BOSB composites.