Calorimetry characterization and crystallization modelling of wax-based mixtures under isokinetic and non-isokinetic cooling
Résumé
Characterization and modelling of wax crystallization must be carefully addressing to understand waxoil organogels formation. During casting process of wax-based mixtures, wax crystallization occurs under concomitant non-constant and high cooling rates. In this study, the crystallization kinetics of two representative wax-based materials was studied by power-compensated Differential Scanning Calorimetry (DSC) with moderate-high cooling rates (from-20 to-200 °C min-1) in constant cooling rates (isokinetic) conditions and simplified non-constant cooling rate (non-isokinetic) conditions. Analyses based on the evolution of the mass fraction of solid wax calculated from heat flow (DSC signal) show similar kinetics trend and enthalpy of crystallization for the different isokinetic conditions, but with a significant influence on the supercooling effects. Considering the limits of the classic Avrami kinetics modelling for high aspect ratio crystals and complex mixtures, a semi-empirical modelling approach of non-isokinetic cooling conditions on a differential form is proposed. The modelling shows a good correlation with experimental results.
Domaines
Sciences de l'ingénieur [physics]
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