Epoxy resins are widely used matrix resins due to their superior thermal properties, chemical resistance, electrical resistance and superior mechanical properties. However, the flammability of epoxy resins greatly restricts their applications. As awareness of fire safety has increased, improving flame retardancy has been the key challenge for epoxy resin research.

Although the addition of halogenated flame retardants to epoxy resin matrices, such as tetrabromobisphenol A (TBBPA), is a fairly effective method to improve the flame retardancy of epoxy resins with electrical and electronic applications, they produce a poisonous and corrosive smoke and can generate highly toxic halogenated compounds during combustion, banned under the REACH environmental regulation.

Since the implementation of environmental directives banning or limiting the use of halogenated compounds, the development of flame retardants based on epoxy resins has focused on more environmentally friendly alternatives. In recent years, a wide spectrum of new halogen-free flame retardants has been developed.

Flame retardants can be incorporated as additives or as reagents, and in recent years, reagent-type formulations are gaining popularity due to their improved performance, although in general, they reduce the mechanical behaviour, thermal resistance and processability of the epoxy resin composition containing them. In addition, flame retardant efficiency is low and combustion produces a large amount of smoke.