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Durabilité des Géotextiles en Polypropylène

Emmanuel Richaud 
Abstract : This thesis deals with the thermo-oxidative ageing of polypropylene geotextiles. The main objective was lifetime prediction from accelerated ageing tests using a non empirical method. Exposure tests with temperatures ranging from 50°C to 130°C under oxygen pressure ranging from 0.02 to 5.0 MPa were performed on stabilized and unstabilized PP samples. These latter contained a phosphite or a phenolic antioxidant in various concentrations. The study of the influence of an aqueous medium on accelerated ageing was also done. Bibliographic data and our experimental results allowed to propose a mechanistic scheme (branched radical chain oxidation) from which a kinetic scheme was derived. A rough analytical solution was used to orientate the numerical resolution of the scheme. The results enable to simulate the kinetic curves of evolution of PP chemical structure in the whole extent of temperature and pressure intervals under study. The kinetic parameters (rate constants and their activation energy) were determined by an inverse method. Model predictions were compared with various features of PP oxidation. This great number of validation tests guarantees the models accuracy. A study of stabilizers effect has not only completed the scheme but also leaded to kinetic parameters that were unknown, and to highlighted existence of elementary reactions (such as a reaction involving phenol and oxygen) that were ignored. Acceleration of ageing by an aqueous media was shown and explained by the fast extraction of stabilizers. Kinetic modelling of the whole ageing process seems feasible although some details remain to be elucidated. Thus, the way for non-empirical geotextiles lifetime prediction is largely open.
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Submitted on : Friday, January 5, 2007 - 8:00:00 AM
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  • HAL Id : pastel-00002053, version 1



Emmanuel Richaud. Durabilité des Géotextiles en Polypropylène. Engineering Sciences [physics]. Arts et Métiers ParisTech, 2006. English. ⟨NNT : 2006ENAM0035⟩. ⟨pastel-00002053⟩



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