Effects of kaolinite nanoroll on the flammability of polypropylene nanocomposites

Abstract Kaolinite nanoroll (Kaol nanoroll) was prepared from raw kaolinite (Kaol), and was then incorporated into polypropylene (PP) with intumescent flame retardant (IFR) to improve the fire performance. The characterization by Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and transmission electron microscope (TEM) revealed that Kaol was transformed from platy to nanoroll. The flammability and thermostability evaluation by limit oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test (CONE) and thermal-gravimetric analysis (TGA) showed that Kaol nanoroll showed better synergistic effect on thermal stability and fire resistance to PP than Kaol. CONE data showed that the peak heat release rate (PHRR) values of PP/IFR (436 kW/m2), PP/IFR/1.5Kaol (372 kW/m2) and PP/IFR/1.5Kaol nanoroll (269 kW/m2) nanocomposites were reduced by 70.3, 74.4 and 81.7% compared to that of neat PP (1474 kW/m2), respectively. The TGA results indicated that Kaol nanoroll can significantly improve the thermal stability and char residues of Kaol PP/IFR nanocomposites. Morphology and structure analysis of char by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) illustrated that Kaol nanoroll was beneficial to improving the char quality of Kaol PP nanocomposite. The FTIR spectra at different temperatures revealed that Kaol nanoroll will promote the formation of charred layers with the P O and P O complexes in the condensed phase to protect the substrate.