What is a flame retardant? What is the principle of flame retardants?-Ammonium polyphosphate APP

In the lives of modern people, flame retardants are almost everywhere. However, people usually can't see it at all, nor know its existence. For most people, there is no idea "what exactly is a flame retardant". In fact, in the mobile phones we carry with us, the computers on the desks, the subways we take every day, the cars we drive, and even the mattresses that make you sleep soundly every night, thousands of flame retardant molecules are like They are always prepared as alert little guards, silently guarding your life and property, and keeping us away from the threat of fire.

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1. What is a flame retardant?

As the name implies, flame retardants are chemical additives that can prevent objects from burning. Adding flame retardants to flammable materials can make the materials difficult to ignite when exposed to an open flame, or easy to extinguish and not spread easily after being ignited. Flame retardants can also reduce heat and reduce smoke emissions.

Flame retardants are not a simple product, but a large family. There are 700 to 800 family members. They can be divided into organic flame retardants and inorganic flame retardants, or halogen, phosphorus, and nitrogen based on reaction elements. And silicon-based, can also be divided into mixed type, additive type and reactive type according to the method of use.

The reason why there are so many types of flame retardants is to satisfy the "tastes" of different materials. Each flame retardant guard has his own job that he is best at, and they can also be used in conjunction with each other to achieve the task of preventing fires with division of labor.

These invisible little guards are active in all aspects of people's lives. They are quietly "lurking" in the circuit boards of various electronic appliances such as mobile phones, computers, TVs, refrigerators, etc. They are also indispensable in the plastic shells of various electronic products, such as the seats of airplanes, ships, and buses, and insulation materials for exterior walls of buildings. They are silently standing by. In developed countries such as Europe and the United States, flame retardants are also widely used in the clothing of people with disabilities such as children, the elderly, and patients. my country has also promulgated national standards, which set clear flame-retardant requirements for building materials and decorations, textiles, furniture, wires, switches, lamps, and home appliances used in public places.

2. different flame retardant principles

It is not an easy task to assume the role of a security guard against fire, and flame retardants must have excellent skills.

Combustion requires three major elements-combustible material, combustion-supporting material (oxygen) and fire source. The combustion process is divided into heating, decomposition, fire, burning and spreading. If you remove any of these elements, or find a way to control the combustion process at the budding stage of heating and decomposition, you can effectively avoid fires.

In preventing flame burning, different types of flame retardants have their own tricks: some prevent combustibles from producing combustible gas by absorbing heat; some form a dense coating on the surface of combustibles to isolate the combustibles from contact with oxygen; Some capture the free radicals participating in the combustion reaction to achieve the purpose of inhibiting the free radical chain reaction; others dilute the oxygen by generating incombustible gas, thereby achieving the effect of slowing the combustion speed.

The inorganic flame retardant Al(OH)3 will decompose after being heated up to 200°C and release crystal water, which evaporates into water vapor when heated. This series of processes will absorb a lot of heat, reduce the temperature of the surface of the material and the flame zone, and slow down the speed of the thermal cracking reaction. In addition, the water vapor generated by the crystal water can also reduce the oxygen concentration and further inhibit the spread of fire.

Phosphorus flame retardant will become a cross-linked solid substance or carbonized layer with a more stable structure when heated, like a solid armor, which wraps up combustibles, which can prevent the material from further pyrolysis and also prevent the internal decomposition of the material. The flammable gas overflows and continues to burn.

The evaporation temperature of the bromine flame retardant is the same or similar to the decomposition temperature of the polymer material. When the polymer material is decomposed by heat, the bromine flame retardant will also volatilize and enter the gas phase combustion zone together with the thermal decomposition products. Flame retardants can quickly capture free radicals in the gas phase combustion zone, inhibit free radical chain reactions, prevent flame propagation, and ultimately slow down the combustion reaction until it stops.

In short, each flame retardant has its own unique secrets.