A process for enhancing the melt strength of polypropylene by extruding said polypropylene in a twin-screw extruder, under inert atmosphere, at a temperature between about 150° C. and about 300° C., and in the presence of about 0.1 to about 3.0 wt %, based on the weight of the polypropylene, of a para-substituted dibenzoyl peroxide.