The ammonium polyphosphate (APP)-pentaerythritol (PT)-melamine (M) system was selected as an intumescent flame retardant (IFR). The influence of dichromic acid-etched polypropylene (EPP) on the properties and compatibility of IFR/polypropylene (PP) composites was studied. The results obtained from mechanical tests and SEM showed that EPP was a true coupling agent for IFR/PP blends, but without changing the necessary flame retardancy. The cocrystallization between bulk PP and PP segments of EPP was confirmed by WAXD analysis. Flow tests showed that the flow behavior of composites in the melt is that of a pseudoplastic liquid, which is significant for EPP's effect on the rheological behavior of IFR/PP composite. (C) 2004 Wiley Periodicals, Inc.