Regenerative Recycling of Automotive Polymer Components: Poly(propilene) Based Car Bumpers

There is a dramatic loss in the mechanical performances at the end of the first life application of bumpers made by a poly(propylene) matrix (PP) and an ethylene-propylene rubber copolymer as dispersed phase. The use of specific additives during the recycling strongly enhances the mechanical properties of these items. The on purpose designed additive contained a regenerative agent and an antioxidant system. The mixing action of the recycling process re-establishes the phase compatibility; the antioxidants inhibit oxidation, which speeds up the degradation reactions in the recycling process; eventually the regenerative agent joins short chains possessing suitable reactive groups. These three effects play a different role in restoring original material performance in dependence of the recycling process: for instance the regenerative agent may be nearly useless if chain scission is not the dominant process in the recycling operation and the interfacial adhesion between rubber and the matrix does not assure automatically a ductile mechanical behaviour under impact conditions.