“…However, polystyrene is easy to burn when heated, which will release toxic gases and a large amount of smoke, and can melt, drip, and flow in the combustion process, thus making the fire spread. Therefore, it is imperative to improve the flame retardant performance of polystyrene. − According to the flame retardant system, it mainly includes mineral flame retardant, halogen flame retardant, phosphorus flame retardant, silicone flame retardant, biobased flame retardant, and so on. − Among them, halogen flame retardants are all the rage, but they are prohibited because of their toxicity and bioaccumulation. ,,− Phosphorus flame retardants have attracted much attention because of their excellent flame retardant efficiency and environmental friendliness, and have gradually become one of the research hotspots in today’s society. ,,,− Phosphorus flame retardants mainly include ammonium polyphosphate, aluminum hypophosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and its derivatives. ,,,, Phosphorus flame retardants will produce phosphoric acid or similar substances during thermal degradation, which can inhibit the combustion process of the condensed phase. In addition, PO · radicals produced by phosphorus flame retardants have a gas phase flame retardant effect. ,, …”