Phytic acid/cellulose nanofibers modified layered double hydroxides flame retardants: Synthesis, properties and applications

Layered double hydroxides (LDHs) tend to agglomerate and primarily exhibit a single condensed phase flame-retardant mechanism, limiting their application as flame retardants (FRs) for wood. In this paper, we prepared a composite FR by intercalating phytic acid (PA) into the LDH layers through anion exchange. Additionally, cellulose nanofibers (CNF) were incorporated to interact with the hydroxyl groups on the LDH surface, improving the dispersion and stability of LDH. LDH-PA-CNF exhibited excellent flame-retardant performance and good dispersibility, which was suitable for flame-retardant modification of wood. After impregnating the wood with LDH-PA-CNF, the total heat release (THR) and total smoke release (TSR) of Wood@LDH-PA-CNF decreased by 21.2 % and 56 %, respectively, compared with the untreated wood. The limited oxygen index (LOI) value of Wood@LDH-PA-CNF has been significantly improved from 21 % to 75.4 %. Based on the analysis of the composition and chemical structure of the residues and gases produced during the combustion of Wood@LDH-PA-CNF, the synergistic flame-retardant mechanism in both condensed and gas phases of LDH-PA-CNF was proposed. This study provides novel insights into the design of high-performance FRs and offers valuable clues for enhancing the homogeneous dispersion and synergistic effects of inorganic FRs.