Synergistic effects of 4A zeolite on the flame retardant properties and thermal stability of a novel halogen-free PP/IFR composite

The synergistic effects of 4A zeolite (4A) on the thermal degradation, flame retardancy and char formation of a novel halogen-free intumescent flame retardant polypropylene composites (PP/IFR) were investigated by the means of limiting oxygen index (LOI), vertical burning test (UL-94), digital photos, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), cone calorimeter test (CCT), laser Raman spectroscopy (LRS) and X-ray photoelectron spectroscopy (XPS). It was found that a small amount of 4A could dramatically enhance the LOI value of the PP/IFR systems and the materials could pass the UL-94V-0 rating test. Also, it could enhance the fire retardant performance with a great reduction in combustion parameters of PP/IFR system from CCT test. The morphological structures observed by digital and SEM photos revealed that 4A could promote PP/IFR to form more continuous and compact intumescent char layer. The LRS measurement, XPS and TGA analysis demonstrated that the compactness and strength of the outer char surface of the PP/IFR/4A system was enhanced, and more graphite structure was formed to remain more char residue and increase the crosslinking degree. Copyright (c) 2013 John Wiley & Sons, Ltd.