What is the solubility of aluminum hypophosphite?

The solubility of aluminum hypophosphite is 0.1g/100ml of water at 25°C. As the temperature increases, the solubility may increase slightly, but not significantly. As a high-quality halogen-free flame retardant, the lower its water solubility, the better. Lower solubility also improves compatibility with plastic resins. If aluminum hypophosphite flame retardants are soluble in water, they may absorb water during the flame-retardant modification process of plastics, leading to changes in material properties and precipitation of the flame retardant. This can cause the material to become soft and sticky, reduce strength, and even promote mold growth. If the flame retardant absorbs water, it can cause plastics and rubber to swell, deform, and lose strength, affecting the product's lifespan and safety.

This explains why ammonium polyphosphate (APP) has poor flame retardant effectiveness in many materials. APP with a relatively low degree of polymerization has some water solubility and is primarily used as a fertilizer. During the flame-retardant process, APP needs to have its degree of polymerization increased to above 2000 to reduce its solubility in water and improve its flame retardant effectiveness in the material. An excellent flame retardant for plastics must possess extremely strong hydrophobic properties. For intumescent flame retardants that rely on forming a dense char layer, water absorption can cause deliquescence and agglomeration during processing or storage. This prevents the material from forming a continuous, intact char layer during combustion, losing its critical role as a barrier to oxygen and heat.