In the field of building fire protection, refractory phosphate materials are crucial, like a solid "safety shield" to protect building fire safety. Many inorganic phosphates, such as aluminum phosphate (AlPO₄), are widely used in building materials, fire-retardant coatings and refractory materials because of their excellent high temperature resistance.

Take aluminum phosphate as an example, it plays a unique role in flame retardant systems. In the intumescent flame-retardant polypropylene (FR-PP) system, such as the system composed of ammonium polyphosphate (APP)/dipentaerythritol (Dper), aluminum phosphate can work synergistically with other components in the system. When heated, APP first degrades and loses water and ammonia to form polyphosphoric acid, which then cross-links with Dper to produce an intumescent carbon layer. In this process, the decomposition rate of some APP is delayed due to the presence of aluminum phosphate. At the same time, aluminum phosphate undergoes a crystal transformation to form aluminum metaphosphate, which has a melting point of up to 1500℃, much higher than the ignition temperature of the material, and exists in the form of solid powder when burning. Due to the thermal oxidation of the sample surface, the aluminum metaphosphate content gradually increases, and due to its high surface tension and bubble effect, it will migrate to the sample surface, blocking the residue surface, improving the density and uniformity of the carbon layer, enhancing the thermal insulation effect of the carbon layer, preventing the transfer of oxygen, combustible gas and heat, and effectively suppressing the spread of fire.

The application of fire-resistant phosphate materials in many parts such as building exterior wall insulation materials, fireproof doors and windows, and fireproof ceilings can significantly improve the fire resistance of building structures, buy precious time for personnel evacuation and fire rescue, and reduce the losses caused by fire.