Ionic liquids modified MXene as a flame retardant synergist for the unsaturated polyester resin

Abstract

I-MXene with excellent dispersibility was successfully prepared using the chemical grafting method with 1-butyl-3-methylimidazole hexafluorophosphate ([BMIM]PF6) onto MXene. It was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), which was added to unsaturated polyester resin (UPR) as a synergistic agent, combined with ammonium polyphosphate (APP) to improve the flame retardancy of composites. Tensile strength of the composites was measured using the electronic universal material testing machine. The results showed that the incorporation of I-MXene was able to increase the tensile strength and elongation at break of the composites. The flame retardancy and thermal stability of the composites were investigated through limiting oxygen index (LOI), cone calorimeter test (CCT), TG and Fourier-infrared spectroscopy (FT-IR). The experimental data showed that the LOI values of I-MXene/APP/UPR composites increased to 29.1%, complying with UL-94V-0 rating. Its peak heat release rate (pHRR) and total heat release (THR) were 19.35% and 16.35% lower than those of APP/UPR composites, and the total smoke production (TSP) was reduced by 10.78%. When heated to 800°C, the amount of residual carbon increased by 7.71%. The catalytic effect of I-MXene contributed to the formation of a compact and expanded carbon layer, resulting in further suppression of heat and smoke release. Highlights: A new type of modified MXene is obtained. It has good dispersivity and synergistic effects. It has good flame retardancy and smoke suppression effects.