FLAME-RETARDANT BEHAVIOR OF UREA–METAPHOSPHORIC ACID COMPLEXES ON CELLULOSE-BASED MATERIALS

In this study, novel urea metaphosphate complexes were synthesized at 1:1, 1:2, and 1:3 molar ratios using urea and metaphosphoric acid to obtain mono-, di-, and trimetaphosphate derivatives (UMP, UDP, and UTP). The synthesized compounds were comprehensively characterized through FTIR spectroscopy, powder X-ray diffraction (XRD), and elemental analysis, confirming their structural frameworks, protonation levels, and compositional features. Crystallographic analysis revealed distinct variations in unit-cell symmetry and packing as the phosphate chain length increased, indicating the formation of progressively more complex hydrogen-bonding networks. The flame-retardant performance of the complexes was examined using treated cellulose-based substrates, including paper, cardboard, and cotton fabric, in accordance with GOST R 50810-95 and GOST 12.1.004-91 standards. Experimental results demonstrated a clear enhancement in flame-retardant efficiency with increasing phosphate content, with UTP exhibiting the highest thermal stability and char-forming capability. Overall, the findings highlight the potential of urea metaphosphate complexes as multifunctional materials with promising applications in both agrochemistry and fire-protection technologies.