Our research team is working on the synthesis of highly flame-retardant and environmentally friendly organic flame retardants for the development of fire-retardant materials and using them to develop acrylic flame-retardant coatings.
Melamine polyphosphate (MPP), a green durable organic phosphate flame retardant, was synthesized from melamine and phosphoric acid, and used for the preparation of flame-retardant coatings. Melamine polyphosphate was synthesized by two-step reactions, which showed that the optimum conditions for the first step reaction of melamine phosphate synthesis were reaction temperature 90 ℃, reaction time 2 h, molar ratio of melamine to phosphoric acid 1:1.2, yield 88%, and the optimum conditions for the second step reaction of polycondensation were polycondensation temperature 290℃, reaction time 3h, and polycondensation conversion 91%. The synthesized melamine polyphosphate is highly resistant to rain-washed action under natural conditions because it is insoluble in water and does not hydrolyze in neutral media, and is therefore used for the flame retardant treatment of protective cloth in outdoor structures. Acrylic flame retardant coatings were prepared using melamine polyphosphate as the main flame retardant, pentaerythritol and titanium dioxide as the secondary flame retardant components and acrylic resin as a binder. The main fire-resistant performance indices of the prepared acrylic fire-retardant coating are characterized by flame resistant time, thermal insulation, mass loss and intumescent index, flame resistant time 25-28 min, thermal insulation 35.2-38.5%, weight loss 4.5-4.9%, and intumescent index 20-22, which have excellent fire-resistant performance. The synergistic effects of MPP as the main flame retardant component, pentaerythritol as carbon source, melamine as gas source, and titanium dioxide as flame retardant synergist were investigated to establish the most suitable combination composition and preparation method, and TGA, DTA, FT-IR, XRD and SEM analyses were carried out to analyze the pyrolysis characteristics and flame retardant mechanism of the acrylic flame retardant coatings. The intumescent char layer formed by carbonization of the flame retardant pyrolysis products during combustion prevents further propagation of continuing combustion because it insulates the heat flux from the outside, prevents the contact with oxygen and inhibits the formation of flammable gases, thus causing the formation of an intumescent char layer and simultaneously extinguishing the flame at its interface. The developed acrylic fire-retardant coatings can be used for fire-retardant treatment of fabrics, wood, paper and other materials, especially for fire-retardant protective clothing of structures that have been kept outdoors for a long time.
The results were published on《Polymer Degradation and Stability》as a title of 《Preparation of acrylic emulsion coating with melamine polyphosphate, pentaerythritol and titanium dioxide for flame retardant cotton/polyethylene terephthalate blend fabrics》(https://doi.org/10.1016/j.polymdegradstab.2023.110366).
