Basic Knowledge of Aluminum Hydroxide Flame Retardants

Aluminum hydroxide is one of the most widely used non-polar flame retardants globally, offering triple functions of flame retardancy, smoke suppression, and drip resistance.

Flame retardants are generally classified into organic and inorganic types. Among them, brominated flame retardants rank among the world's largest organic flame retardants, offering advantages such as high flame retardancy efficiency, low required additive levels, and broad applicability, playing a significant role in flame retardancy applications. However, brominated flame retardants also present certain drawbacks, such as significantly reducing the UV stability of the treated substrate and generating increased smoke, corrosive gases, and toxic fumes during combustion. In contrast, aluminum hydroxide inorganic flame retardants offer advantages including superior thermal stability, absence of corrosive gases, non-volatility, long-lasting effectiveness, non-toxicity, and low cost. They pose minimal environmental hazards. Therefore, driven by environmental protection and fire safety requirements, eco-friendly inorganic flame retardants will gradually replace halogen-containing organic flame retardants.

Aluminum hydroxide is one of the most widely used non-polar flame retardants globally, offering triple functions of flame retardancy, smoke suppression, and drip resistance. During combustion, it produces no secondary pollution; upon pyrolysis, it releases no toxic or corrosive gases. Instead, it absorbs heat and releases water vapor, imparting flame retardancy and self-extinguishing properties to polymeric materials. Not only does it exhibit excellent dispersibility, but it also synergistically interacts with other flame retardants like magnesium hydroxide to enhance flame retardancy. Due to its low polarity, aluminum hydroxide demonstrates good compatibility with polymers and other macromolecular materials, leading to its widespread adoption and steadily increasing usage.

As flame retardants see broader application, deeper insights into their properties have emerged. The long-term hazards of halogenated flame retardants to the environment and human health have been identified, making halogen-free formulations, smoke suppression, and toxicity reduction the forefront of current and future flame retardant research.

Aluminum hydroxide flame retardants are extensively used in domestic and international markets. Descriptions of their self-ignition processes vary depending on the polymer type employed. Generally, the flame-retardant effect of ATH is considered the result of several synergistic mechanisms. Thus, the flame-retardant mechanisms of aluminum hydroxide flame retardants are as follows:

1.  Endothermic Effect: Dehydration begins at 170°C, absorbing heat and inhibiting polymer temperature rise.

2. Covering function: After dehydration, ATH forms an Al₂O₃ protective film on the combustible surface, isolating oxygen and preventing further combustion.

3. Carbonization: Under combustion conditions, the flame retardant produces strong dehydration products that carbonize the plastic, minimizing the generation of flammable volatiles and thus inhibiting flame spread.

4. Dilution: ATH filling reduces the concentration of combustible polymers. Water vapor released during ATH dehydration dilutes combustible gases and oxygen, thereby inhibiting combustion.

Aluminum hydroxide flame retardants play an increasingly vital role in flame retardancy due to their non-toxicity and moderate cost.