Aluminum hypophosphite flame retardant has a high decomposition temperature and is one of the main raw materials for halogen-free flame retardants such as PP, TPE, TPU, and PBT. AHP has good thermal stability, but its thermal decomposition process is complex, producing numerous decomposition products.

200℃ Dehydration Stage: Small amounts of water of crystallization or adsorbed water on the material surface are lost first. This stage is not significant for pure aluminum hypophosphite.

300℃ Decomposition Stage: This is the crucial stage for its flame-retardant effect. H₂PO₂⁻ is unstable and decomposes upon heating, producing PH₃ and phosphoric acid (or polyphosphoric acid). PH₃ is a reducing gas that can be oxidized by oxygen in the air, consuming free radicals and thus interrupting the combustion chain reaction. Al³⁺ reacts with the phosphoric acid produced during decomposition to form aluminum phosphate. AlPO₄ is a ceramic-like substance with extremely high thermal stability. As the thermosetting temperature continues to rise, AlPO₄ may generate a small amount of Al₂O₃ and a stable char layer. Aluminum hypophosphite decomposes to produce aluminum phosphate salts, which catalyze the dehydration of polymers to form char, creating a dense char layer that isolates oxygen and heat transfer. The decomposition process is largely endothermic, lowering the material's surface temperature. PH₃ oxidizes in the flame to generate free radicals such as PO₄·⁻, which capture H⁻ and OH⁻ to interrupt the combustion chain reaction; water vapor dilutes the concentration of combustible gases and oxygen. The high char residue of aluminum phosphate extends the heat transfer path, improving flame retardant durability. It is important to note that the PH₃ produced during decomposition is highly toxic and flammable, and can become explosive when mixed with air.

Microencapsulation of AHP or its combination with MCA and zinc borate can reduce PH₃ release, improve compatibility, and enhance flame retardant efficiency. Our company produces surface-coated aluminum hypophosphite, which improves its decomposition performance, reduces flame retardant release, and enhances dispersibility and compatibility.