The free radical functionalization of immiscible blends of polybutylene succinate (PBS) and polypropylene carbonate (PPC) was successfully achieved on a novel quad screw extruder. A premade compatibilizer, PPC-grafted-maleic anhydride (gPPC), was added in various amounts to trigger the chemical compatibilization and tailor the properties of the final blend. Titration of acid groups on the functionalized blends showed that the grafting efficiency increases with the addition of gPPC. Proton NMR corroborated the formation of new graft copolymers in the reactive blends. A change in the rheological behavior of the formulations evidenced the grafting reactions occurring at the interphase of the components. Also, gPPC suppressed droplet coalescence as seen in the SEM images. Finally, the addition of compatibilizer increased the tensile strain at break by more than 100%, improved up to 50% the impact resistance, and produced a small increase on flexural and elastic modulus.