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After the incorporation of the polyaniline (PANI), polymethyl methacrylate (PMMA) composites with outstanding electrical conductivity had been widely used in sensors. However, the flame retardancy of PMMA composites seriously restrained its further application. Thus, phosphorus‐containing polyaniline (FR‐PANI) was successfully prepared and combined with PMMA. The flame retardancy, electrical conductivity, thermal stability, and fire behavior of the resultant PMMA/FR‐PANI composites were systematically studied. When the loading amount of FR‐PANI was controlled at 20 wt%, the PMMA matrix was endowed with dramatic flame retardancy, exhibiting a limiting oxygen index of 29.1% and a UL‐94 V‐0 rating in vertical burning tests. Meanwhile, the volume resistivity was also reduced up to 0.5 MΩ. The thermal stability of the PMMA/FR‐PANI composites was enhanced by the formation of abundant char residue, which improved the fire behavior of the PMMA matrix. The effect of FR‐PANI on the flame retardancy of the PMMA matrix was deduced on the basis of thermogravimetry‐infrared, Fourier transform infrared, and scanning electron microscopic analyses. The phosphorus‐containing functional groups in the FR‐PANI molecular chain underwent thermal degradation in the condensed phase and promoted the formation of a char layer. The char layer, in turn, prevented heat transfer into the interior of the PMMA composites, serving as a barrier to the volatilization of flammable micromolecules. Therefore, FR‐PANI is an important candidate to extend the range of applications of PMMA to include multifunctional intelligent sensors. [ABSTRACT FROM AUTHOR]

Nano-silica had been used as a synergistic agent for the preparation of aluminum diethylphosphinate (AlPi) flame retardant polyamide 66 (PA66/AlPi) and PA66/AlPi/nano-silica composites through twin-screw extrusion. The limiting oxygen index (LOI), used to characterize the minimum amount of oxygen needed to sustain a candle-like flame, revealed that the PA66/10%AlPi/1%nano-silica composites exhibited an excellent flame retardant efficiency with a high LOI value of 32.3%. The vertical flame test (UL-94) revealed that the PA66/10%AlPi/1%nano-silica composites passed the V-0 rating without drop melting. Cone calorimeter test revealed that the heat release rate and total heat rate for the PA66/10%AlPi/1%nano-silica composites were significantly decreased by 51.1 and 16.8%, respectively, compared with those of pure PA66. The thermogravimetric analysis showed that the PA66/10%AlPi/1%nano-silica composites had vast chars of 8.1% even at 800°C, indicating that nano-silica could promote the char formation of the PA66 composites. Scanning electron microscopy indicated a solid and tough residue of the burned PA66/10%AlPi/1%nano-silica composites as compared with the very loose and brickle residue of the burned pure PA66, indicating that a suitable amount of nano-silica played a synergistic effect in the flame retardancy. [ABSTRACT FROM AUTHOR]