Twin-screw extruders (TSE) are widely used for compounding and polymer blending operations mainly because of their flexibility in providing varying levels of dispersive and distributive mixing independently. TSEs have also been used as a continuous reactor for chemical reactions, such as polymerization and compatibilization, to take place. It is known that the reaction conversion can be improved using different process condition: temperature, screw speed and screw configuration are some example of parameters that can influence the reaction kinetics. However, not much is known about reactive extrusion when it comes to the evaluation of the reaction in-processing and along the extruder barrel, especially when the process condition is varied. In this work, the evaluation of the effect of the screw configuration in twin-screw extruder on the kinetic of the compatibilization reaction of PA and PP-g-AA was evaluated by on-line MIR. The on-line ATR/MIR method, developed in house, was used to follow the reaction conversion along the extruder barrel in different location upstream the die, in real time. The area ratio of the peak of carbonyl stretching in amide present in PA6 at 1640 cm-1 standardized to the IR area of the peak at 1170 cm-1 relative to PP is applied to evaluate the evolution of the reaction of compatibilization between the amine end group in the chain of PA6 and acrylic acid grafted in the PP chain. Higher aggressiveness of the screw configuration, which can be related with its dispersive mixing power, influences the conversion of the reaction and, therefore, should have a significant impact in its kinetics. In order to study the extent of this influence, four screw profiles were chosen to impose different types of flow in the melt, mild and aggressive extensional mixing elements recently developed by Maia and co-workers and mild and aggressive kneading blocks.