Magnesium-aluminum flame retardants mainly are magnesium hydroxide and magnesium aluminum layered double hydroxide. Now, here will introduce these two flame retardants.
Magnesium hydroxide flame retardant has flame retardant, smoke suppression, fills functions. It does not produce secondary pollution and accounts for more than 80% of inorganic flame retardant.
Magnesium hydroxide is nontoxic, noncorrosive and good stability. It does not produce toxic gases at high temperatures, it is considered to be the most promising. Compared with aluminium hydroxide (ATH), it has a higher thermal stability. As the decomposition temperature is about 3 4 0 ℃, about 100 ℃ higher than ATH, so it can be used for many engineering plastics. Its heat-absorbing is about 17% higher than ATH; smoke-suppressant is better than ATH; hardness is lower than ATH, this extend the life of flame retardant polymer.
Thermal decomposition temperature of magnesium hydroxide is 140 ℃ higher than that of aluminum hydroxide, this makes the synthetic material that add magnesium hydroxide withstand higher processing temperatures, also it helps to improve efficiency of flame retardant. The diameter of magnesium hydroxide particles is small, so it has small wear to equipment.
Because magnesium hydroxide has more advantages than the aluminum hydroxide, the proportion of consumption of magnesium hydroxide is growing. Compared with similar inorganic flame retardant, magnesium hydroxide has have better smoke-suppressant effect. It has no harmful emissions during the process of production, use and waste, also neutralize the acidic and corrosive gases produced in the combustion process.
Layer aluminum magnesium double hydroxide (LDH)
LDH is one of the most common and good thermal stability of double hydroxide. Because of its layers contain changeable anions, layered double hydroxides (LDHs) also called anionic clay. As a kind of important clay minerals, it has been widely used in various areas of industrial production, such as flame retardants, catalyst precursors, medical use antacids, ultraviolet, and infrared absorption materials, catalyst carriers, barrier materials, disinfection materials, PVC stabilizer, adsorption, anion exchanger, solid ion battery and so on.
The flame retardant mechanism of LDH: layer-like double hydrogen oxidation magnesium aluminum has tablets layer structure. There has hydroxy on layer board and crystal water between layers. Due to this special structure and composition, it absorb large heat when heated and decomposition, it can reduced burning system of temperature; decomposition release of water can dilute and barrier combustible gases; decomposed products are alkaline porous material, bigger than surface and can adsorb harmful gas, especially acid gas; Zn, Mg plasma exist in layer tablets is elimination smoke of effective component.
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