Preparation and synergistic flame retardancy of intrinsic P/Si-containing polyurethane with hBN for wood

Driven by the increasing demand for wooden furniture, polyurethane (PU) with flame-retardant properties is widely used in woodworking. In this work, 6-(3-(2,3-dihydroxypropoxy)propyl)dibenzo[c, e] [1, 2] oxaphosphinine 6-oxide (DG) was synthesized via addition reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 3-allyloxy-1,2-propanediol. Subsequently, DG and hBN were incorporated into the PU matrix, dual crosslinking agents triethanolamine and triethoxy(3-glycidyloxypropyl)silane were introduced and the PU was then applied to wood via hot-pressing and coating methods. Compared with unmodified flame retardant wood, the modified wood achieves UL-94 V-0 rating with reduced heat release rate by 26.25% and total heat release by 14.04%. Moreover, thermogravimetric analysis confirms enhanced thermal stability, with T 5% rising from 258 ℃ to 273 ℃ and 800 ℃ residue 13.36% to 23.01%. Simultaneously, the PU exhibits excellent water resistance, with water absorption rates remaining below 3% after 24 h of immersion. This study develops and demonstrates a novel strategy for fabricating wood-based flame-retardant composites, which yields high-performance PU coatings that combine excellent flame retardancy with water resistance for wood product applications.