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Vers une approche mécanistique du vieillissement thermique du polyprophylène à l'état fondu au cours du rotomoulage

Abstract : Abstract : Rotational moulding is a polymer processing technique for the production of hollow parts. The main drawback of rotational moulding is a long stay of polymer in its molten state at high temperature. To prevent any significant polymer thermal degradation, it is necessary to define, preliminary, a processing window. The objective of this thesis is to build up, by a mechanistic approach, a kinetic model of thermal degradation allowed to define certain significant boundaries of the processing window, such as thermal degradation threshold. The general model is then composed of two levels. The first level is devoted to the thermal model predicting, in any point of a polypropylene part (PP) in development, the local evolution of temperature. This model is derived from thermal transfer mechanisms occurring during polymer processing, phase changes, polymer melting and crystallization, being simulated using an enthalpy method. Its validity is checked for various processing conditions of machine components (furnace, mould, polymer and internal air). The second level is devoted to the chemical model predicting local degradation conversion rate. This chemical level is derived from an oxidation mechanistic scheme of stabilized PP in molten state. Its validity is checked from oxidation products concentrations, mass losses and oxidised layer thickness measured experimentally on thin films and thick pieces exposed to isothermal (between 170 and 230 °C) and dynamic conditions (typically in real rotomoulding conditions, from 170 to 250 °C). The general kinetic model, composed of both coupled levels, allows to predict antioxidants consumption during processing by rotational moulding for different operating conditions. For example, for a furnace maintained at 300 °C, model predicts an induction period of 22 min. At 350 °C, part is stable during 15 min.
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Submitted on : Tuesday, June 23, 2009 - 8:00:00 AM
Last modification on : Thursday, January 11, 2018 - 6:20:30 AM
Long-term archiving on: : Thursday, September 30, 2010 - 8:48:02 PM


  • HAL Id : pastel-00004925, version 1



Salah Sarrabi. Vers une approche mécanistique du vieillissement thermique du polyprophylène à l'état fondu au cours du rotomoulage. Sciences de l'ingénieur [physics]. Arts et Métiers ParisTech, 2009. Français. ⟨NNT : 2009ENAM0003⟩. ⟨pastel-00004925⟩



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