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Inorganic phosphorus flame retardants

Inorganic phosphorus flame retardants2016.11.30

Phosphorus-based flame retardants is not a new type flame retardant. But as a halogen-free systems, it is popular in the field of flame retardant. Phosphorus flame retardants are the most important one among flame retardants. There are inorganic phosphorus flame retardant agent and organophosphate flame retardants. And organophosphorus flame retardants play an important role.

Inorganic phosphorus flame retardants

Inorganic phosphorus flame retardants include red phosphorus, ammonium Polyphosphate and phosphate.

Phosphate flame retardants include di-sodium hydrogen phosphate, lithium iron phosphate, magnesium phosphate, sodium phosphate, diammonium phosphate, phosphoric acid antimony and so on. Diammonium hydrogen phosphate is generally used in synthetic fibers and rubber, rigid and flexible foams, forest fire, paper, wood; but disodium hydrogen phosphate is used in the textile, paper, and wood fire-retardant.


Ammonium Polyphosphate (APP) is considered a good performance of inorganic flame retardant. White powder, decomposition temperature greater than 256℃, polymerization degree between 10-20 is water soluble, and it is poorly soluble in water when degree of polymerization is larger than 20. APP is cheaper than organic flame retardants, low toxicity and good thermal stability. It can be used individually with other flame retardant compound for flame retardant. The use of APP is wide, one of the most important use is as a source of acid and use with carbon source and gas sources, consisting of intumescent flame retardant system. Also it can be used for other fire-retardant plastics, fibers, rubber, paper, wood, large areas fire fighting of forest and coalfield.

Red phosphorus is an inorganic flame retardant with high performance. Compared with other flame retardants, add less can reach the same levels of flame retardant, therefore it has small impact on the physical and mechanical properties of the material. However, ordinary red phosphorus has one big disadvantage, that is it easily absorb moisture oxidation and release toxic phosphine gas in the oxidation process. And common red phosphorus has poor compatibility with plastics and difficult to disperse in plastic. Besides, red phosphorus is deep red, which limits its use in polymers. In order to improve some of these shortcomings, the surface treatment of phosphorus is the main direction of research, and the most effective method is microencapsulation. Mechanism of flame retardant of red phosphorus is: heated to decomposition to form strong dehydration of metaphosphoric acid, so that the burning of polymer surface carbonized. Carbonized layer can reduce the release of flammable gases, as well as heat effect. In addition, PO • free radicals which is formed by red phosphorus and oxygen go into the gas phase can capture large H•、HO• free radicals. Next time, OKCHEM will add details about organic phosphorus flame retardants. If you have interest, please follow us at OKCHEM Linkedin Page or visit, thanks!

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