Abstract
The effects of fillers, including ammonium polyphosphate (APP), aluminium trihydrate (ATH) and talc, and the effect of polyethylene vinyl acetate (EVA) as an interfacial agent, were investigated on the flame retardant properties of intumescent polypropylene (PP), by using mechanical testing, to measure the tensile and Izod impact strengths, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and the limiting oxygen index (LOI) test method. SEM studies showed that the dispersion of flame retardant particles in the PP matrix improved with the use of EVA. Tensile strength decreased but elongation at break and impact resistance of PP/APP/EVA and PP/ATH/EVA composites increased by using 10 wt.% of EVA. Using 12 wt.% of talc in PP/APP/PA-6/EVA led to increasing impact resistance and decreasing tensile strength and elongation at break of the composite. EVA prevented the exudation of additives to the composite surface, and consequently the fire retardant properties of the composites improved. Talc increased fire protective performance due to the formation of a ceramic-like protective shield at the surface and increased residual mass at the end of the process. The results were interpreted by means of thermal decomposition, chemical reaction between components, and the formation of a protective layer at the surface on ignition.