PC flame retardants exert their flame-retardant effect through mechanisms such as heat absorption, coverage, control of chain reactions, and asphyxiation by non-combustible gases.
The heat released during combustion is finite. If some of the heat released can be absorbed quickly, the flame temperature will decrease, radiation will ignite the surface, and the vaporized combustible molecules will decompose into free radicals, thus controlling combustion to some extent. At high temperatures, PC flame retardants undergo a strong endothermic reaction, absorbing some of the heat released during combustion, lowering the surface temperature of the combustible material, controlling the formation of combustible gases, and preventing the spread of combustion. This type of PC flame retardant, combined with water vapor, fully utilizes its endothermic properties to enhance its flame retardancy.
Applications of PC Flame Retardants
After adding flame retardants to combustible materials, the flame retardants form a glassy or stable foam covering layer at high temperatures, blocking oxygen, preventing heat insulation, oxygen separation, and the escape of combustible gases, thereby achieving flame retardancy. For example, organophosphorus PC flame retardants can produce more structurally stable cross-linked solids or carbonized layers during heating. The formation of a carbonized layer prevents further polymer degradation and also prevents pyrolysis products from entering the gas and participating in the combustion process.
With the widespread use of polymer materials and consumer electronics, the incidence of fires is rising, and the losses are alarming. The flame retardancy of polymer materials is becoming increasingly important, with PC flame retardants playing an indispensable role. The future development direction of polycarbonate (PC) flame retardants will be effective, green, and environmentally friendly.
PC flame retardants are used to improve the flame retardancy of polymer materials, increase their ignition point, or reduce their burning rate, thus extending rescue time, saving lives, and reducing losses. Based on structure, PC flame retardants can be divided into polymer PC flame retardants and small molecule PC flame retardants. Based on different application methods, additive PC flame retardants and reactive PC flame retardants can be further divided into halogenated PC flame retardants and halogen-free PC flame retardants, depending on whether the material contains halogens. However, additive PC flame retardants are mainly used in thermoplastic polymer materials, physically existing within the polymer material without chemically reacting with other components. Reactive PC flame retardants are mainly used in thermosetting polymer materials, participating in the chemical reactions that synthesize the polymer and becoming structural units within it. Upon ignition, a vigorous oxidation reaction occurs, releasing a large number of hydroxyl groups. These hydroxyl groups are highly reactive and readily combine with other substances to produce organic compounds such as water. These other organic compounds then combine with oxygen and decompose to form new organic compounds. Combustion continues in this cyclical process.
