At present, the flame retardants widely used in the world are halogen series (mainly chlorine and bromine series), phosphorus series (including halogen-phosphorus series), and inorganic flame retardants (mainly Mg(OH)2 and Al(OH) 3]. Halogen-based flame retardants (especially bromine-based) and phosphorus-based flame retardants have good flame retardant effects, but they are expensive and have environmental protection issues, so their use is restricted. Therefore, inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide, which are highly efficient, strong in smoke suppression, non-toxic, and harmless, are more and more favored by users.
In recent years, due to several major fires, secondary pollution caused by incineration of plastics, the emergence of Dioxin issues, and increasingly strict environmental protection, the plastic industry has forced the plastics industry to switch to non-toxic, pollution-free, and inhibitory products. Inorganic flame retardants for smoke, and brominated flame retardants, which account for a large market share, are gradually being restricted. The 8th World Flame Retardant Conference was held in the United States in 1997. The meeting pointed out that the future development direction of flame retardants will focus on high-efficiency, low-toxicity, and low-smoke flame retardants. A considerable part of the conference report involves magnesium hydroxide Flame retardants and aluminum hydroxide flame retardants, which all show that inorganic flame retardants (especially magnesium hydroxide and aluminum hydroxide have a broad space for development.
So how do choose flame-retardant magnesium hydroxide and aluminum hydroxide?
In addition to the equivalent impact on the environment, magnesium hydroxide is compared with aluminum hydroxide in terms of thermal reaction, decomposition temperature, applicable polymers, flame retardant ability, smoke suppression ability, and acid stability. Magnesium hydroxide Flame retardants are better than aluminum hydroxide flame retardants, and also better than traditional halogen and phosphorus flame retardants. Specifically in:
(1) The flame retardant mechanism of the two is similar. The thermal decomposition process of magnesium hydroxide and aluminum hydroxide is: the gaseous water generated by thermal decomposition can cover the flame, expel oxygen, dilute the combustible gas, and form an insulating layer on the plastic surface in contact with the flame to prevent the flow of combustible gas and prevent The spread of flame is similar to the charring effect of phosphorous flame retardants. The decomposition products of these two flame retardants are non-toxic substances and produce mineral phases, especially MgO, which has a stronger neutralizing ability with acids than aluminum hydroxide and can quickly neutralize the acidity and corrosion generated during the combustion of plastics. Gases (SO2, NO2, CO2, etc.);
(2) The thermal decomposition temperature of magnesium hydroxide is 330°C, which is 100°C higher than that of aluminum hydroxide. Therefore, plastics filled with magnesium hydroxide flame retardant can withstand higher processing temperatures, because in the plastic processing process Increasing the processing temperature is beneficial to speed up the extrusion speed and shorten the molding time;
(3) The decomposition energy of magnesium hydroxide (1.37kJ/g) is higher than that of aluminum hydroxide (1.17kJ/g), and the heat capacity is also 17% higher, which helps to improve the flame retardant efficiency;
(4) Magnesium hydroxide has a strong carbonization effect and a large amount of carbonization, thus improving the flame retardant efficiency and reducing the amount of smoke;
(5) Magnesium hydroxide has a stronger smoke suppressing ability than aluminum hydroxide. In EPDM resin, 75% magnesium hydroxide flame retardant and 25% aluminum hydroxide flame retardant are mixed and added with aluminum hydroxide. Compared with flame retardants, the smoke output of the former is significantly reduced;
(6) The hardness of magnesium hydroxide particles is smaller than that of aluminum hydroxide, so the friction on the equipment is small, which is beneficial to prolong the life of the production equipment;
(7) With the improvement of the production process, the technology for producing magnesium hydroxide flame retardant with bittern as the raw material is becoming more and more mature, and its production cost will be greatly reduced. Therefore, the advantages of magnesium hydroxide flame retardants are obvious, and there is a tendency to replace aluminum hydroxide.
In summary, magnesium hydroxide is the first choice for flame retardants.
