After the industrialization of rigid polyurethane foam, its application range has gradually expanded. At the same time, people have come to realize that it is extremely important to improve the flame retardancy of foams. Many countries have formulated flame retardant specifications for materials in construction, transportation, and other sectors, and specified flame retardant standards for different use occasions. Therefore, the flame retardancy of rigid polyurethane foams is based on objective needs, otherwise the scope of application will be greatly limited.

Due to the efforts of scientists for many years, flame-retardant rigid polyurethane foams have developed rapidly, and many foam plastics with certain flame retardancy have been industrialized. However, rigid polyurethane foam is an organic polymer material after all, and it is a flammable material. Its limiting oxygen index [O] is generally around 17. Once it is on fire, due to its large surface area and low thermal conductivity, the material is easy to burn and difficult to burn. Self-extinguishing, it is impossible to burn without burning in the flame.

Therefore, the so-called flame retardant or flame retardant, actually refers to a specific standard or a specific standard of a test method. Generally, for small fires, the foam can still burn in a fire. A foam with good flame retardancy can self-extinguish in case of small fire, which is not easy to cause fire; in the fire, the fire spread can reduce the risk of fire spread and irritating toxic fumes.

The proportion of flame-retardant rigid polyurethane foam in rigid polyurethane foam has increased year by year and has increased to 70%-80%. The specific requirements for flame retardation are: not easy to catch fire; low flame spread, minimum smoke; less harmful gases generated during combustion.

Flame retardants for rigid polyurethane foams should have the following conditions:

　　①The amount of addition is small and the effect is good;

　　②Good miscibility with raw materials;

　　③Little impact on the performance of foam plastics;

　　④Non-toxic or very toxic to ensure safe use;

　　⑤Low price;

　　⑥The flame retardant effect does not decrease with the passage of time;

　　⑦The viscosity of the liquid flame retardant should not be too large;

　　⑧Does not corrode equipment.

　　In fact, flame retardants that fully meet the above conditions are difficult to obtain. A typical flame retardant is only generally capable of certain conditions.