Mechanism of Flame-Retardant Aluminum Hydroxide

In the flame retardant market, demand for halogen-based flame retardants has been steadily declining, replaced by halogen-free, low-toxicity alternatives.

In the flame retardant market, demand for halogen-based flame retardants has been steadily declining, replaced by halogen-free, low-toxicity alternatives. Among these, flame-retardant aluminum hydroxide stands out, supplied by aluminum hydroxide manufacturers.

Currently, flame-retardant aluminum hydroxide accounts for over 80% of global inorganic flame retardant consumption. It possesses three primary functions: flame retardancy, smoke suppression, and filling. It does not produce secondary pollution during combustion, exhibits synergistic effects with various substances, and is non-volatile, non-toxic, minimally corrosive, and cost-effective. Widely recognized both domestically and internationally, it is extensively used as an environmentally friendly flame retardant. The mechanism of aluminum hydroxide flame retardancy is as follows:

(1) Heat Absorption and Cooling Effect

At 300-350°C, it dehydrates and absorbs heat. Due to water's high specific heat capacity, its conversion to steam absorbs significant thermal energy from the surroundings, thereby preventing temperature escalation in polymers.

(2) Dilution

The steam generated from aluminum hydroxide dehydration dilutes the concentration of flammable gases and oxygen, inhibiting combustion.

(3) Surface Coverage

After dehydration, aluminum hydroxide forms an aluminum oxide protective film on combustible surfaces, blocking oxygen and preventing further combustion.

(4) Carbonization

Under combustion conditions, the flame retardant generates strong dehydrating substances that cause plastics to carbonize without producing flammable volatiles, thereby preventing flame spread. However, as aluminum hydroxide is an inorganic flame retardant, it exhibits performance differences with polymeric materials. Poor affinity between the two leads to uneven dispersion when directly filled. Larger particle sizes also become stress concentration points in composites, creating weak points that not only limit flame retardancy but also severely impact the mechanical properties of the product.

When used alone, aluminum hydroxide requires a loading exceeding 60% to achieve effective flame retardancy. Such high concentrations adversely affect plastic processing, physical, and mechanical properties. Consequently, surface-treated aluminum hydroxide demonstrates superior flame retardancy.