Polypropylene/polypropylene-grafted-maleic anhydride/glass fiber reinforced polyamide 66 (PP/ PP-g-MAH/GFR PA 66) blends-composites with and without the addition of polypropylene-grafted-maleic anhydride (PP-g-MAH) were prepared in a twin screw extruder. The effect of the compatibilizer on the thermal properties and crystallization behavior was determined using differential scanning calorimetry analysis. The hold time was set to be equal to 5 min at 290 degrees C. These conditions are necessary to eliminate the thermomechanical history in the molten state. The crystallization under nonisothermal conditions and the plot of Continuous-Cooling-Transformation of relative crystallinity diagrams of both PP and PA 66 components proves that PP is significantly affected by the presence of PP-g-MAH. From the results it is found that an abrupt change is observed at 2.5 wt % of PP-g-MAH as a compatibilizer and then levels off. In these blends, concurrent crystallization behavior was not observed for GFR PA66. (c) 2007 Wiley Periodicals, Inc.