With the expansion of the application of polymer composites and the increase of their dosage, the application of flame retardant materials and the flame retardant technology have also been developed and improved. Phosphorus flame retardants are widely used because of their variety and excellent flame retardant properties. In the future, the research of phosphorus flame retardants should be more inclined to the development direction of flame retardants with high thermal stability and good miscibility.

Flame retardant is an assistant used to prevent materials from being ignited and flame propagation. It is mainly used for flame retardant synthesis and natural polymer materials. It is an indispensable chemical material in our life. Since the extensive use of organic synthetic polymer materials, human beings have begun to face new fire threats. At present, the form of global fire is very severe. Therefore, flame retardant, as a chemical additive, is particularly important.

(1) Categories and basic requirements of flame retardants:

According to the relationship between flame retardants and flame retardants, flame retardants can be divided into two categories: additive type and reactive type. The former is only physically dispersed in the substrates and is mostly used in thermoplastic polymers. The latter is used as monomer or assistant reagent to participate in the synthesis of polymers, and eventually become the structural unit of polymers, mostly for thermosetting polymers.

According to the flame retardant elements, the commonly used flame retardants are divided into halogen, organic phosphorus and halogen-phosphorus, nitrogen, phosphorus-nitrogen, antimony, aluminum-magnesium, inorganic phosphorus, boron, silicon, molybdenum and so on. There are also a class of intumescent flame retardants and a kind of nano-inorganic substance, which can form flame-retardant polymer-inorganic nanocomposites with a series of polymers.

(2) What are the basic elements of flame retardants?

(1) High flame retardant efficiency

(2) It should have the following ecological and environmental characteristics:

1. It is harmless to human beings, animals and plants.

2. Difficult migration

3. Less toxic or corrosive gases released during hot cracking and combustion

4. Easy to recycle without deteriorating or slightly deteriorating the performance of mechanical recycled products

5. Compatibility with the Environment

(3) Good compatibility with flame retardant substrates

(4) Sufficient thermal stability

(5) Processing properties of flame-retardant substrates should not be deteriorated too much.

(6) Acceptable optical stability

(7) The source of raw materials is abundant, the manufacturing process is simple and the price is acceptable to users.

It is noteworthy that an ideal flame retardant is best able to meet the above conditions, but this is almost impossible. Therefore, when choosing practical flame retardants, most of them are based on meeting the basic requirements, compromising among other requirements and seeking the best comprehensive balance.