Characterization of Contamination Effects for Two Polypropylene-Based Materials Daniel Pessey, 1 Nadia Bahlouli, 1 Claude Raveyre, 2 Jacques Guillet, 2 Said Ahzi, 1 Jean-Marie Hiver, 3 Abdesselam Dahoun 3 1 Universite ´ de Strasbourg, IMFS, 2 rue Boussingault, 67000 Strasbourg, France 2 Universite ´ Jean Monnet, LRMP, 23 Rue Paul Michelon, 42023 Saint-Etienne Cedex 2, France 3 Ecole des Mines de Nancy, LPM, Parc de Saurupt, 54000 Nancy, France In this work, contamination effects are studied on two polypropylene-based materials. These effects were identified on the molecular weight and on rheological and mechanical properties. Model contaminants cho- sen in this study were ethylene glycol and engine oil. They were added during the extrusion process to simu- late the degradation due to contaminants. To quantify contamination effects and to correlate them with the microstructure evolution, scanning electron micro- scope (SEM) analyses were also conducted. The analy- sis of the different obtained results led to a better understanding of the mechanisms involved in the con- tamination process. Contaminants slightly affect the rheological properties, whereas mechanical properties are more influenced. These observations are confirmed by the modification of the fractured surfaces of the materials due to the presence of contaminants observed on SEM micrographs. POLYM. ENG. SCI., 00:000–000, 2009. ª 2009 Society of Plastics Engineers INTRODUCTION Composites based polymeric matrix such as polypro- pylene are increasingly becoming preferred engineering materials for structural applications in the automotive industry. The principal reason comes from the fact that these materials offer a good mechanical resistance such as a good stiffness, a large plastic strain, an acceptable elastic limit, as well as an excellent chemical resistance. Furthermore, the economical and environmental context compels the automotive industry to focus now their efforts on the recycling process of automotive composite polymers. These recycled composites can contain particles such as elastomers like EPDM (ethylene-propylene-diene monomer), EPR (ethylene propylene) copolymers, and/or fillers like talc, carbon black. To understand the effects of these second phases, several works [1–5] reported the strong influence of particles on the microstructure and on the mechanical behavior of thermoplastics. In addition, the recycled composites may also contain impurities and contaminants like ABS, oils, dusts, etc. This article deals with the degradation due to contami- nants which act as impurities on composite based polymers. It is important to firstly study contaminants effects before working on recycling effects due to modifications of the material properties induced by their presences. The chosen contaminants, in this study, are the engine oil (called EO) and the ethylene glycol (called EG) used for instance in the composition of the brake liquid. They were chosen because their presence has been determined in vehicles parts at the end of the vehicles lifetime [6]. The effects of these two contaminants on composite based polymer were not been studying in depth. However, few existing works deal with the degradation due to these impurities [7]. They may con- stitute extremely critical heterogeneities with regard to the life-span of these materials. On the other hand, some stud- ies reported that oil or EG is introduced in polymer blends and composites as compatibilizers [8–11]. In this case, some mechanical properties improvements are expected. For instance, Kallel et al. [7], Alexander and Thachil [9], and Othman et al. [11] showed that oil and an oil fatty acid used as compatibilizers improves the mixing of the compo- sites or polymer blends leading to an increase of the tensile strength while the Young’s modulus decreases. In the poly- mer filled with rigid particles, the polymer itself solely con- tributed to the elasticity of the composite. Concerning the presence of the EG in a polymer blend or a composite, lim- ited studies have been conducted: for instance, Kallel et al. [7] reported that a small polar molecule such as EG can form a third phase leading to understand that EG is not mis- Correspondence to: Said Ahzi; e-mail: ahzi@imfs.u-strasbg.fr Contract grant sponsor: Ministe `re de la Recherche et de l’Innovation (France). DOI 10.1002/pen.21451 Published online in Wiley InterScience (www.interscience.wiley.com). V V C 2009 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE—-2009