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Cinétiques d'imbibition et de dissolution de matériaux poreux

Abstract : The aim of this work is to understand the coupled processes of imbibition and dissolution of a porous material. One more particular question concerns the influence of a surfactant on the dissolution kinetics. First of all, we show that imbibition kinetics can be deduced from the porous structure of tablets. In fact, a linear relation, known as Washburn law, is observed between the square of the wetted length and the time. When imbibition is coupled with dissolution, a modification of this law, through the introduction of a linear dissolution term, leads to a good agreement between theoretical and experimental data. Then, the experimental study of tablets dissolution evidences three kinetics regimes according to tablets porosities. For the most porous tablets, the disintegration is very fast as the whole tablet is wetted by water in a few seconds. Opposingly, the less porous tablets dissolve slowly according to an erosion process. In this case, the imbibition is much slower than powder dissolution. Intermediate regimes can be encountered when both processes are competing. Also, we experimentally evidence that the trapped gas that is present inside the tablet evacuates through the largest pores of the material. We then focus on the delaying effect of the surfactant on the dissolution mechanism. It results from the slowing down of imbibition due to a modification of wetting properties. In fact, once dissolved in water, the surfactant decreases the liquid surface tension and increases its viscosity.
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Submitted on : Monday, March 31, 2008 - 4:17:10 PM
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  • HAL Id : tel-00268285, version 1

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Nelly Brielles. Cinétiques d'imbibition et de dissolution de matériaux poreux. Matériaux. Université Sciences et Technologies - Bordeaux I, 2007. Français. ⟨tel-00268285⟩

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