Aluminum hypophosphite has a high phosphorus content and exhibits excellent flame retardant effects in PP, TPE, TPU, and wires and cables. However, it lacks smoke suppression. This formulation incorporates zinc borate to reduce smoke generation. Below, we introduce a low-smoke halogen-free flame retardant formulation for aluminum hypophosphite. All raw materials are halogen-free.

Aluminum hypophosphite: 50kg

Hydrotalcite: 30kg

Zinc borate: 20kg

Diatomaceous earth: 8kg

Magnesium hydroxide: 6kg

Aluminate coupling agent: 2kg (The above data are in mass ratio.)

Zinc borate releases water of crystallization during the initial combustion phase, absorbing a large amount of heat and lowering the material surface temperature. At higher temperatures, it reacts with HCl produced from the decomposition of polymers (especially halogen-containing polymers such as PVC) to generate ZnCl2 and boric acid/boron oxide. ZnCl2 is a strong Lewis acid that catalyzes dehydration, cross-linking, and charring reactions in oxygen-containing polymers such as cellulose or aromatic polymers. This promotes the formation of a dense and robust char layer on the material surface. B2O3 melts at high temperatures, forming a viscous, glassy coating that physically covers the material surface and the resulting carbon layer.