Preparation of Phosphate‐Modified Melamine Formaldehyde Resin and Its Application for Flame‐Retardant Cellulose Paper

ABSTRACT There is a need to improve the flame retardancy of melamine formaldehyde (MF) resins used in construction materials and industrial applications. In this study, modified MF resin was obtained using eco‐friendly methods and reagents; specifically, ultrasonic treatment was performed in an aqueous solution containing disodium hydrogen phosphate (DSP) and phosphoric acid. Fourier transform infrared, X‐ray photoelectron spectroscopy, and nuclear magnetic resonance spectroscopy confirmed that the phosphate‐modified MF resin (PMF) was produced by the treatment. Elemental analyses showed that the condensation reaction occurred at the hydroxymethyl group and amine groups of MF resin to form methylene bridges, and the reaction rate and elemental composition of PMF powder were changed depending on the ratio of MF/DSP reaction medium. PMF can be in situ coated on the cellulose paper with pad‐sonication‐cure treatment. Scanning electron microscope confirmed the presence of numerous micro‐sized PMF particles coated on the paper surface. Thermogravimetric analysis revealed that the PMF‐treated paper increased the production of residues and charred materials. Differential scanning calorimetry revealed that the PMF‐treated paper exhibited heat absorption characteristics. Vertical burning tests on paper treated with PMF powder demonstrated that it was nonflammable and had a limiting oxygen index (LOI) of 32, sufficient to prevent further combustion.