Polystyrene nanospheres coated red phosphorus flame retardant for polyamide 66

As a halogen‐free flame retardant, red phosphorus (RP) is unstable in air due to its slow oxidation. The shortcomings of RP include strong water absorbing proneness, high friction sensibility and poor thermal stability. The characteristics of polystyrene (PS) are thermostability and fluidity in melt, which can improve the compatibility of RP and the organic matrixes. Using PS as a coating material can improve the characteristics of strong water absorbing proneness of RP. Herein, the polystyrene nanospheres coated RP (PSNS@RP) flame retardant was successfully prepared via emulsion polymerization of styrene. The result shows that the release of phosphine from the PSNS@RP is greatly reduced. The ignition point is increased by about 200°C, and the moisture absorption rate can be reduced by 40 times. The effect of PSNS@RP on the flame retardancy and thermal stability of polyamide 66 (PA66) were studied in detail. Compared with PA66, the limiting oxygen index (LOI) of the PSNS@RP/PA66 composite is increased from 24.8% to 34.2%. The flame retardant grade is enhanced to be UL94 V‐0. The peak heat release rate (PHRR) is decreased from 1444.5 to 420.9 kW m−2, the total heat release (THR) is decreased from 145.8 to 94.2 MJ m−2, and the total smoke production (TSP) is also reduced by 35%. Therefore, the as‐synthesized PSNS@RP has excellent flame retardant and smoke‐suppressing properties for PA66.