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What kind of substance is flame retardant and what specific function does it have? Let's give you a detailed introduction in these aspects, so that you can quickly understand the flame retardant.
The way to realize flame retardant
The mechanism of gas phase flame retardancy. That is to say, it can inhibit the freedom of chain growth in combustion reaction and play the role of flame retardant.
The mechanism of condensed phase flame retardancy. It prevents the thermal decomposition of polymer and the release of combustible gas in solid phase.
Interrupt heat exchange mechanism. That is, the heat generated by the polymer is taken away without feedback to the polymer, so that the polymer does not decompose continuously.
Classification of flame retardants
According to the types of elements, it can be divided into halogen system, organic phosphorus system, halogen phosphorus system, nitrogen system, silicon system, aluminum magnesium system, molybdenum system, etc. There are intumescent flame retardants, charring flame retardants and so on. According to the chemical structure, it can be divided into inorganic flame retardant, organic flame retardant, polymer flame retardant, etc. According to the relationship between flame retardant and flame retardant materials, it can be divided into additive flame retardant and reactive flame retardant. Reactive flame retardant participates in the chemical reaction of polymer.
1 halogenated flame retardant
Halogenated flame retardant is one of the largest organic flame retardants in the world. Halogenated flame retardants are mainly used in electronics and construction industry, about 50 ~ 100 kinds of halogenated flame retardants cover most of the market demand.
The reason why halogen flame retardants are valued by people is that halogen flame retardants have high flame retardant efficiency and moderate price, and their performance price ratio is difficult to compare with other flame retardants. In addition, halogen flame retardants have many varieties and wide application range, so they are favored by people. However, halogen flame retardants generate more smoke and corrosive gases during pyrolysis or combustion, and are troubled by dioxin problems.
More than 80% of the halogenated flame retardants are used in electronic / office equipment and construction industry, mainly styrene and its copolymers, thermoplastic engineering plastics and epoxy resin.
2 phosphorus containing flame retardant
Phosphorus containing compounds can be used as flame retardants for thermoplastic, thermosetting plastics, fabrics, paper, coatings and adhesives. These flame retardants include red phosphorus, water-soluble inorganic phosphate, insoluble ammonium polyphosphate, organic phosphate and phosphonate, phosphine oxide, hydrogen elastic alkyl phosphate and bromoaryl phosphate.
Although halogen flame retardants have high flame retardancy, they have problems of environmental pollution and toxicity. Phosphorus flame retardants are very effective flame retardants except for several kinds of polymers such as styrene and polyolefin, and have little secondary pollution. Therefore, the flame retardants have attracted people's attention.
Map and DAP are still effective flame retardants for fibers, fabrics, nonwovens, paper and wood. They can form phosphoric acid, which esterifies the hydroxyl group of cellulose, and decomposes the cellulose into carbon, which changes the thermal degradation process, so as to achieve the purpose of flame retardant. They are soluble in water, so their flame retardancy is not durable. It is one of the main components of intumescent flame retardant.
Red phosphorus is a very effective flame retardant, which can be used in oxygenated polymers, such as PC, pet, PBT, PPE. It is widely used as a flame retardant for nylon parts in Europe. Because red phosphorus reacts with water in the atmosphere to form toxic phosphine, industrial products need to be stabilized and coated.