Aluminum hypophosphite has excellent flame retardant properties for polypropylene (PP), wire and cable, and potting compounds. Its flame retardant efficiency is particularly enhanced when combined with MCA flame retardants or melamine hydrobromide (MHB). Aluminum hypophosphite flame retardants feature small particle size, good dispersibility, high whiteness, and excellent temperature resistance. So, can aluminum hypophosphite flame retardant TPU be flame retardant? Let's briefly discuss this.

TPU, short for thermoplastic polyurethane, has an oxygen index of 17.9%, making it a relatively flammable polymer. Without flame retardant modification, its applications are significantly limited. TPU offers numerous advantages, including low-temperature resistance, excellent elasticity, high mechanical strength, creep resistance, and oil resistance. However, combustion produces large amounts of harmful gases such as HCN and CO. Traditionally, flame retardants containing bromine, such as magnesium hydroxide and aluminum hydroxide, have been used to achieve flame retardancy. However, bromine-based flame retardants are environmentally unfriendly, and the excessive addition of inorganic flame retardants significantly impacts the material's physical properties. Both of these flame retardant methods are unsuitable for TPU applications. Aluminum hypophosphite flame-retardant TPU has garnered significant attention in the materials industry in recent years.

TPU flame-retardant formulas:

There are numerous formulations for aluminum hypophosphite flame-retardant TPU, with a commonly used ratio of 1:2: AHP:MCA flame retardant, and a 12-15% addition of the composite flame retardant.

Effects:

The oxygen index (LOI) is increased to 27%, achieving a flame retardancy rating of UL94 V-0. Thermal stability is enhanced, and the char formation rate is significantly improved.

Flame-retardant mechanism:

When the TPU flame retardant reaches its decomposition temperature, it produces phosphorus-containing, non-flammable gases, including phosphoric acid and polyphosphoric acid. These gases dilute the combustible gases, absorb heat from the material, and form a large char layer, preventing oxygen from entering the combustion zone, reducing the escape of combustible gases, and delaying or inhibiting combustion.

The use of aluminum hypophosphite in flame-retardant TPU formulations has been successful in some cases, while its effectiveness has been less pronounced in others. Research and analysis suggest that moisture or the formulation may have a role in this effect. Since TPU is not resistant to strong polar solvents and strong acid and alkali media, although flame retardants are not polar solvents, nor are they strong acids or bases, the phosphorus-containing polymers produced after compounding are generally weakly acidic, which may affect TPU materials. TPU flame retardant formulations are still under continuous improvement in the industry, requiring our halogen-free flame retardant technicians to overcome difficulties and improve flame retardancy.