Following our studies on chemical modification proceses of polypropylenes by maleic anhydride, some new experimental works are shown here that check the possibilities of processing atactic polypropylene in the melt by a batch process. A modified polymer that is supposed to be useful as an interfacial agent if used in heterogeneous systems based on polypropylene is also clearly obtained. The favorable effect of the nonstereoregularity of the polymer can be noted. This polymer has a higher level of modification than the stereoregular polymer (isotactic polypropylene), despite the lower processing temperature used that causes a decrease in the initiator activity. Otherwise, this article deals with the role played by the reaction time during the process. A mechanism of chemisorption and some considerations about the fractal nature of the reaction kinetics are proposed to explain the results obtained.