Flame retardation behavior of polybenzoxazine/α-ZrP nanocomposites
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© 2016 The Royal Society of Chemistry. Flame retardation behaviors of polybenzoxazine (PBa) nanocomposites containing various levels of exfoliated α-zirconium phosphate (α-ZrP) nanoplatelets were prepared and confirmed by transmission electron microscopy. Thermogravimetric analysis (TGA) and cone calorimetry results indicate that exfoliated α-ZrP could drastically enhance the thermal stability of PBa and promote high char formation of PBa. Additionally, α-ZrP greatly enhances the flame retardancy of PBa. The time to ignition was increased to 91 s for PBa/α-ZrP-4.6 wt% as opposed to 73 s for pristine PBa. The peak heat release rate value of PBa was significantly reduced by nearly 50% with 8.4 wt% addition of α-ZrP. The char residue analyses using scanning electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy suggest the participation of α-ZrP in the charring process. The volatile products formed in the thermal degradation processes of PBa and PBa/α-ZrP were analyzed by a TGA-Fourier transform infrared spectrometer and found that exfoliated α-ZrP facilitate the formation of a compact and homogeneous char layer, which contains flame retardant elements (N, P and Zr) on the surface of the materials, during burning. The improved flame retardancy of PBa/α-ZrP is mainly attributed to a combination of the greatly increased melt viscosity of PBa and matrix fast swelling due to the formation of the pyrolytic gases. Additionally, exfoliated α-ZrP is found to greatly reduce the amount of toxic gases containing C-O groups. Instead, it releases phosphorous-containing species to achieve flame retardancy in the gas phase. The implication of the present study for the preparation of fire retardant polymers is discussed.
author list (cited authors)
Zhao, C., Li, P., He, D. a., Li, Y., Lei, F., & Sue, H.