The flame retardant mechanism of unsaturated polyester resin:
The flame retardancy of FRP pipes is usually achieved by adding flame retardants to the resin matrix. According to different methods of use, flame retardants can be divided into additive type and reactive type. Additive flame retardants mainly play the role of flame retardants by adding flame retardants in combustibles. The reactive flame retardant is to introduce flame retardant groups into the polymer material through chemical reaction, so as to improve the flame resistance of the material, to prevent the material from being ignited and to suppress the spread of flames. Among the types of flame retardants, additive flame retardants dominate, and are widely used, accounting for about 85% of the flame retardants, and reactive flame retardants only account for 15%.
The flame retardant exerts its flame retardant effect through several mechanisms, such as endothermic effect, covering effect, chain reaction inhibition, suffocation effect of non-combustible gas, etc. Most flame retardants achieve the purpose of flame retardant through a combination of mechanisms.
According to the flame retardant elements, flame retardants can be divided into halogen flame retardants, phosphorus flame retardants, nitrogen flame retardants, phosphorus-halogen flame retardants, phosphorus-nitrogen flame retardants and other categories. During pyrolysis, halogen flame retardants decompose X• and HX, which capture and transfer combustion free radicals. HX can dilute the combustible gas generated during the cracking of combustible materials, and cut off the contact between combustible gas and air. Phosphorus-based flame retardants produce phosphoric anhydride or phosphoric acid during combustion, which promotes the dehydration and carbonization of combustibles and prevents or reduces the generation of combustible gases. Phosphoric anhydride also forms a glass-like melt when pyrolyzed to cover the surface of combustibles, promoting its oxidation to generate carbon dioxide, which plays a flame retardant role. In nitrogen-based flame retardants, nitrogen compounds and combustibles act to promote cross-linking to carbon, reduce the decomposition temperature of combustibles, and generate non-combustible gas, which acts to dilute combustible gases. Phosphorus-halogen flame retardants and phosphorus-nitrogen flame retardants mainly achieve the purpose of flame retardancy through the synergistic effect of phosphorus-halogen and phosphorus-nitrogen, with the dual effects of phosphorus-halogen and phosphorus-nitrogen, and the flame retardant effect is relatively good .