Fabrication of multifunctional polymethyl methacrylate composites based on phosphorus‐containing polyaniline with excellent flame retardancy and electrical conductivity

Abstract

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.