The chemical and morphological structure of new and post-consumer ten years old poly(propylene) based car bumpers has been investigated and their mechanical properties have been correlated to the chemical and physical degradation of the material. Poly(propylene) matrix and a rubbery ethylene-propylene phase were the constituents of the bumpers. A strong impairment of the mechanical properties has been found in old samples which showed also a distinctive phase separation. The modification of the chemical structure was much less evident: oxidation on the exposed surface involving the poly(propylene) phase has been highlighted in old bumpers, and possible crosslinking. These relatively small changes, however, are responsible for the pronounced physical ageing. A tentative explanation is a poor interfacial adhesion of rubber particles from which the crazes can propagate further to form cracks.
Natural Ageing of Automotive Polymer Components: Characterisation of New and Used Car Bumpers” / M. LUDA DI CORTEMIGLIA; G. RAGOSTA; P. MUSTO; A. POLLICINO; G. CAMINO; A. RECCA; V. NEPOTE. - In: MACROMOLECULAR MATERIALS AND ENGINEERING. - ISSN 1438-7492. - 287(2002), pp. 404-411.