The Box-Wilson experimental design method is employed to study the free radical process between polypropylene and maleic anhydride in the presence of a peroxide like radical initiator. The batch processes in the solution and in the molten state have been considered in an attempt to know how the physical characteristics of the reaction medium are affecting the modification level of the polypropylene. The analytical titration method proposed by Gaylord is used in order to evaluate the maleic anhydride grafting onto the polypropylene. The main goal of this preliminary study is to know and to show the quantitative values reached in the grafted maleic anhydride level inside the experimental range scanned. From the results the influence of the reaction and several observations can be made in order to evaluate and finally optimize the continuous process by reactive extrusion.