Most phosphorus containing flame retardants can significantly improve their flame retardant effect when used in conjunction with compounds containing nitrogen or halogens. Previous studies have investigated the mechanisms of phosphorus nitrogen and phosphorus halogen synergistic systems, but there are few reports on the synergistic flame retardant effect of phosphorus silicon. Organic silicon flame retardants are a new generation of non halogenated carbon based flame retardants that are efficient, eco-friendly, anti droplet, and smoke suppressant. They not only improve the processing performance, mechanical properties, and heat resistance of substrates, but also have excellent recycling effects on flame retardant materials. Organic phosphorus flame retardants have excellent flame retardant properties, low toxicity, and good heat resistance. When organic silicon flame retardants are used together with organic phosphorus flame retardants, they not only have significant synergistic flame retardant effects, wide applicability, and obvious complementarity, but also have bright development potential and application prospects.

The synergistic flame retardant mechanism of phosphorus and silicon is that when phosphorus and silicon flame retardants are used, phosphorus will catalyze the formation of carbon at high temperatures, while silicon increases the thermal stability of these carbon layers, thereby exerting the synergistic flame retardant effect of phosphorus and silicon. Moreover, the flame retardant synergistic effect of phosphorus silicon is further enhanced when using siloxane instead of silane, because the layered silica formed by the degradation of siloxane prevents the oxidation of the carbon layer, thereby improving the stability of the carbon layer.

Application of phosphorus/silicon synergistic flame retardant system: In recent years, people have begun to pay attention to the application of phosphorus silicon compounds in cotton fabric flame retardant finishing, which not only reduces the toxicity of phosphorus flame retardants, but also lowers the price of silicon flame retardants, and has a good synergistic flame retardant effect. The phosphorus silicon synergistic flame retardant system includes two aspects: one is to compound phosphorus based flame retardants with silicon based flame retardants, and produce synergistic flame retardant effects through the interaction between flame retardants; On the other hand, introducing phosphorus and silicon elements into the same molecular structure produces a synergistic flame retardant effect through the interaction between the elements.