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Polyurethane foam flame retardant technology
Time:2020/5/15 10:17:53    

Classification of polyurethane foam flame retardant technology

The flame retardant technology of polyurethane foam (PUF) is divided into structural flame retardant and additive flame retardant technology.

The structural flame retardant is directly grafted on the reaction raw materials (such as polyol or isocyanate) to participate in the reaction. The flame retardant component added in the additive flame retardant technology is called additive flame retardant.This kind of flame retardant can be a non-reactive but flame retardant substance, disperse it uniformly in the PUF matrix to prevent combustion, it is also possible to add substances containing flame retardant elements such as chlorine, bromine, and phosphorus to the raw materials, and some or all of them participate in the combustion,the resulting material acts as a flame retardant.

3 burning stages of polyurethane foam

The combustion of PUF can be divided into 3 stages.

The first stage is heat accumulation: due to the low thermal conductivity of PUF, it will quickly heat up once heated.

The second stage is thermal decomposition and combustion: when the temperature rises to the decomposition temperature of PUF, the material will degrade and decompose to produce a large amount of combustible gas, and the combustible gas will react with oxygen and then burn.

The third stage is heat transfer and flame spread: the large amount of heat generated by the combustion is continuously conducted to the adjacent area, so that the flame spreads and continues burning.

Types of flame retardants used

The flame retardants used in PUF can be divided into halogen flame retardants, phosphorus flame retardants, nitrogen flame retardants, boron flame retardants, filled flame retardants and intumescent flame retardants according to flame retardant components. Halogen flame retardants are no longer promoted or even banned.

Phosphorus flame retardant

  Phosphorus flame retardants can be divided into inorganic and organic types. Inorganic phosphorus flame retardants mainly include red phosphorus and phosphate; organic phosphorus flame retardants mainly include phosphate, phosphite, hypophosphite, organic phosphorus salts and phosphorus heterocyclic compounds, etc,.  

Nitrogen flame retardant

  Nitrogen-based flame retardants are mainly melamine and its salts (such as cyanurate, phosphate, borate, dicyandiamide and guanidine salts, etc.).

Boron flame retardant

  Boron flame retardants are classified into inorganic boron flame retardants and organic boron flame retardants.The most widely used inorganic boron flame retardant is zinc borate, which has good flame retardant properties and good smoke suppression.When the zinc borate is heated to above 300 , it releases crystalline water and absorbs a lot of heat.The resulting B2O3 glass-like film can be coated on the polymer to play a role of heat and oxygen barrier.

Filler type flame retardant

Filler type flame retardant is the largest amount of polymer flame retardant, its price is low and its stability is good, but the filling amount is large and the flame retardant efficiency is low. The main filler-type flame retardants include A12 (OH) 3, Mg (OH) 2, CaCO3. Among them, the Mg / A1 flame retardant has the functions of flame retardant, filling and smoke suppression.

Intumescent flame retardant

  The intumescent flame retardant is generally composed of dehydrating agent, carbon forming agent and gas source. The PUF added with an intumescent flame retardant will form a uniform carbon foam layer on the surface when it is heated, it plays the role of heat insulation, oxygen barrier, smoke suppression, and prevention of solution generation and has a flame retardant effect.

Compound flame retardant

  To improve the flame retardant performance of PUF, two or more flame retardant elements are usually put into the flame retardant, it can be the same type of flame retardant or different types of flame retardants.

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