Preparation of modified fly ash hollow glass microspheres using ionic liquids and its flame retardancy in thermoplastic polyurethane

In this article, a new type of flame-retardant HGM@[EOOEMIm][PF6] was prepared by modifying fly ash hollow glass microspheres (HGM) with ionic liquids 1-((ethoxycarbonyl)methyl)-3-methylimidazolium hexafluorophosphate([EOOEMIm][PF6]). The physical and chemical characteristic of HGM@[EOOEMIm][PF6] was tested by scanning electron microscope-energy-dispersive spectrometer and X-ray photoelectron spectroscopy, respectively. The flame-retardant characteristics including heat and smoke production of TPU composites were investigated using cone calorimeter test (CCT) and limiting oxygen index, etc. The CCT results revealed that the heat release rate (HRR), total smoke release, and smoke factor and so on decreased greatly with the addition of HGM@[EOOEMIm][PF6]. For example, when the loading of HGM@[EOOEMIm][PF6] was 0.125 mass%, the peak HRR value of the sample was decreased to 779.3 kW m(-2) (TPU2), reduced by 23.7% compared with TPU1 (1021.1 kW m(-2)) containing the same loading of HGM. The thermal degradation behaviors of TPU composites have also been indicated by thermogravimetric analysis/infrared spectrometry (TG-IR). The TG-IR results showed that HGM@[EOOEMIm][PF6] could not only improve the thermal stability of TPU composites at high temperature, but also reduce the aromatic compounds as the smoke precursors. In all, HGM@[EOOEMIm][PF6] will make a great influence in improving the flame retardancy of TPU.