This article deals with the study of the efficiency of different compatibilizing agents in the intumescent polypropylene/polyamide-6/ammonium polyphosphate (PP/PA-6/APP) blend. The migration of additive was first investigated by X-ray photoelectron spectroscopy. The study showed that ethylene-butyl acrylate-maleic anhydride is not efficient in preventing the exudation of APP to the surface. However, ethylene vinyl acetate (EVA) prevented such a phenomenon. Second, the modifications in the blends were analyzed as a function of their compositions. Optical microscopy analysis showed that adding EVA to PP/PA-6/APP promoted a decrease in the size of PA-6 droplets. X-ray diffraction was used to characterize the effect of each component on the PP crystallinity. It was clearly shown that the crystallinity depends on the composition of the blend. (C) 2004 Wiley Periodicals, Inc.