Synthesis of heptamolybdate-intercalated MgAl LDHs and its application in polyurethane elastomer

Abstract

Heptamolybdate (Mo7O246−) was intercalated in the interlayer space between MgAl-layered double hydroxides (Mo-MgAl LDHs) by the hydrothermal and ion exchange method, and then polyurethane elastomer (PUE) based composites were prepared by the prepolymerization method with different amounts of Mo-MgAl LDHs. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, laser Raman spectroscopy (LRS), and scanning electron microscopy (SEM) were employed to characterize the obtained LDHs. The performance of the PUE/LDHs were evaluated by measuring their thermal gravimetric, heat release rate (HRR), and smoke density (Ds). The results show that PUE/LDH composites exhibit a lower peak heat release rate (pk-HRR), Ds, and a prolonged combustion time, in comparison with neat PUE. Comparison between NO3-MgAl LDHs and Mo-MgAl LDHs containing composites show that the introduction of Mo6+ is able to facilitate flame retardance and smoke suppression efficiency, which results mainly from the presence of MoO3 derived from the decomposition of Mo7O246− intercalated LDHs. Mo-MgAl LDHs reduce the pk-HRR of composites by 39% with only 1 wt.% content, and the maximum Ds of composites is reduced to a minimal value of 274 with 10 wt.% Mo-MgAl LDHs. More importantly, LDHs would improve the mechanical properties at a low content. The experimental results reveal the potential of Mo7O246− intercalated LDHs to improve both the flame retardancy and smoke suppression of PUE. Copyright © 2015 John Wiley & Sons, Ltd.