High-Melting-Point PBAT-Based Polyurethane Hot-Melt Adhesives for Robust, Moisture-Resistant and Reusable Wood Bonding

Developing wood adhesives that combine high performance with practical durability remains a critical challenge. Here we report a polyurethane reactive hot-melt adhesive (PUR) engineered with high-melting-point poly(butylene adipate-co-terephthalate) (PBAT) as the soft segment. By systematically varying the terephthalic acid (PTA) molar fraction, the melting temperature and crystallinity of both PBAT and the resulting PURs were precisely tuned from 57.5 to 144.2 °C. The optimized high-melting-point PURs demonstrate exceptional adhesion to beech wood (lap-shear strength >7.0 MPa), outstanding resistance to moisture and nonpolar solvents, and robust retention of bonding performance after thermal conditioning across the broad temperature range of −100 to 100 °C. Specifically, a thermally reactivatable shield-and-liberate mechanism, arising from rapid crystallization of the PBAT phase, enables crystallization shielding and thermal liberation of unreacted isocyanate groups, underpinning intrinsic reusability: PUR50 retains 56.2% of its initial strength after five bonding-debonding cycles. Among the series, PUR50 (50 mol % PTA of dibasic acid) achieves the best balance among adhesive strength, environmental durability, and thermal reactivatability. This work establishes a rational molecular-design strategy for next-generation wood adhesives meeting the dual demands of high performance and reusability.