ADP-P@Mn and ADP-P@Ni composites were prepared by the interfacial assembly of ammonium dihydrogen phosphate (ADP) with transition metal–phytic acid (PA) complexes. These composites were then mixed with cellulose fibers in an aqueous solution to produce flame-retardant paper. Morphological analysis revealed that the original ADP particles exhibited a smooth, cubic morphology; however, after functionalization with phytic acid, the particles became rougher. The presence of P–O–Mn and P–O–Ni bonds confirmed the bridging effect between phytic acid and ADP, which led to reduced crystallinity and promoted synergistic flame-retardant effects during combustion. Within all concentration ranges tested, both ADP-P@Mn and ADP-P@Ni exhibited significantly improved flame retardancy compared with pristine ADP and reduced the flame spread rate by up to 50%, showing remarkably enhanced flame-retardant efficiency. Notably, even at low concentrations, these two novel flame retardants endowed cellulose paper with self-extinguishing properties. Additionally, increased carbon and oxygen contents in residual char, along with cross-linking via P–C, P–O, and P═O bonds, indicated the formation of a dense carbonaceous layer. Consequently, ADP-P@Mn and ADP-P@Ni significantly enhanced the flame resistance of cellulose paper while maintaining its excellent writing performance, moisture resistance, and mechanical properties.
Cui et al. (2026) studied this question.