Brief Analysis: Reasons for the Popularity of Flame Retardants

With the development of the polymer materials industry, synthetic materials such as plastics, rubber, and fibers are increasingly used in areas such as construction, chemical, military, and transportation. Due to the flammability of polymer materials, flame retardant technology has become a global concern. With the increasing environmental awareness of various countries and the promulgation of flame retardant regulations, the flame retardant market has grown rapidly. Currently widely used flame retardants include halogen (mainly chlorine and bromine), phosphorus (including halogen-phosphorus), andinorganic flame retardants, mainly Mg(OH)₂ and Al(OH)₃). Halogen (especially bromine) and phosphorus flame retardants are effective but expensive and have environmental concerns, so their use isrestricted. Therefore, highly efficient, smoke-suppressing, non-toxic and harmless inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide are increasingly favored by users.

Apart from their similar environmental impact, when compared in terms of thermal reaction, decomposition temperature, applicable polymers, flame retardant ability, smoke suppression ability, and stability against acids, magnesium hydroxide flame retardants are superior to aluminum hydroxide flame retardants and also better than traditional halogen and phosphorus flame retardants.

Specifically, this is shown in the following ways:

(1) Both have similar flame retardant mechanisms. The thermal decomposition process of magnesium hydroxide and aluminum hydroxide is as follows: the gaseous water generated by thermal decomposition can cover the flame, expel O₂, dilute combustible gases, and form an adiabatic layer on the plastic surface in contact with the flame to prevent the flow of combustible gases and prevent the spread of flames, which are similar to the carbonization effect of phosphorus flame retardants. The decomposition products of both flame retardants are non-toxic substances that produce mineral phases, especially MgO, which has a stronger neutralizing ability against acids than aluminum hydroxide and can quickly neutralize acidic and corrosive gases (such as SO₂, NO₂, CO₂, etc.) produced during plastic combustion.

(2) The thermal decomposition temperature of magnesium hydroxide is 330°C, which is 100°C higher than that of aluminum hydroxide. Therefore, plastics with magnesium hydroxide flame retardants can withstand higher processing temperatures. As the increase in the processing temperature during plastic processing is conducive to accelerating extrusion speed and shortening molding time.

(3) The decomposition energy of magnesium hydroxide (1.37kJ/g) is higher than that of aluminum hydroxide (1.17kJ/g), and its heat capacity is also 17% higher, which helps improve flame retardant efficiency.

(4) Magnesium hydroxide has a strong carbonization effect and a large amount of carbonization, which improves flame retardant efficiency and reduces smoke production.

(5) The smoke suppression ability of magnesium hydroxide is stronger than that of aluminum hydroxide. In EPDM resin, compared with adding only aluminum hydroxide flame retardant, adding a mixture of 75% magnesium hydroxide flame retardant and 25% aluminum hydroxide flame retardant reduces less smoke production significantly.

(6) The hardness of magnesium hydroxide particles is smaller than that of aluminum hydroxide, so it has less friction on equipment and is conducive to extending the life of production equipment.