The application of aluminum hypophosphite flame retardants has received increasing attention from various industries in recent years. Its phosphorus content is significantly higher than that of similar halogen-free flame retardants, and its application in PPV-2, TPE, and potting compounds is currently quite mature. Polyurethane sealants have a low oxygen index and are easily flammable. Halogen-free flame-retardant formulations are relatively few, and the application of aluminum hypophosphite in the flame retardant field of polyurethane sealants is still in the early research and exploration stage. Below is a brief introduction to the aluminum hypophosphite flame-retardant polyurethane sealant formulation.

1. Formulation:

Ammonium polyphosphate (APP): 41.6%; Aluminum hypophosphite LXF-A24138 flame retardant: 8.4%; Other additives as needed.

2. Effect:

The oxygen index of the composite polyurethane sealant material reaches 35%.

3. Precautions:

Choose a high-degree-of-polymerization model of ammonium polyphosphate (APP). Careful selection of the aluminum hypophosphite model is crucial; ordinary, low-temperature-resistant, and low-stability models can have a significant adverse effect on the formulation.

The mechanism of action of aluminum hypophosphite flame-retardant polyurethane sealant is basically the same as that of phosphorus and nitrogen flame retardancy, involving phosphorus-nitrogen synergy, char formation flame retardancy, and gas-phase condensation flame retardancy. It should be noted that adding a small amount of charring agent, such as a triazine macromolecular charring agent, may improve the flame retardant effect. Theoretically, yes, but the amount added in actual flame retardant processes needs further verification. The above formulation has a relatively large amount of flame retardant added, which has a certain adverse effect on the material properties. Further improvements to this formulation require the addition of other synergistic agents.