Polypropylene is a versatile commodity polymer used in a wide range of applications, from car bumpers to prescription pill vials. A deficiency of polypropylene is its strength when impacted. The impact properties of polypropylene can be greatly improved by incorporating rubber, creating a heterophasic polypropylene. While heterophasic polypropylene can have great impact properties, the addition of rubber reduces the stiffness of the polymer and limits its ability to be processed. Processability is determined by the viscosity of the polymer during processing and is controlled through the molecular weight of the polymer chains. Unfortunately, as the molecular weight is decreased to improve processability, the impact properties of polymer suffer, requiring the addition of more rubber. The balance of these performance attributes—impact, stiffness and processability—is difficult to achieve in polypropylene. Milliken’s DeltaMax 3000i modifies the heterophasic polypropylene through a reactive process that improves the balance of impact, stiffness and processability. Controlled rheology, a common process for reducing molecular weight to improve processing, involves adding organic peroxides to the polypropylene.