Using polyamide-6 as charring agent in intumescent polypropylene formulationsI. Effect of the compatibilising agent on the fire retardancy performance

Addition of the ammonium polyphosphate/polyamide-6 blend is known to enable fire properties of interest to be obtained in many polymers. However, the use of an interfacial agent is required to stabilise the formulation. This study investigates the improvement of the fire performance induced by incorporation of ethylene–butyl acrylate–maleic anhydride (EBuAMA) and ethylene vinyl acetate (EVAx, where x is the vinyl acetate weight level) as interfacial agents of the polypropylene/ammonium polyphosphate/polyamide-6 blend. It is shown that the improvement strongly depends upon both the nature and the amount of interfacial agent used.