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Étude rhéo-optique des mécanismes de dispersion de mélanges sous cisaillement simple. 1 Mélanges concentrés de polymères immiscibles. 2 Mélanges polymères-charges poreuse

Abstract : Rheo-optical tools (optical microscopy) were developed and used to study in-situ dispersion mechanisms in complex blends: concentrated immiscible polymer blends and polymer-porous filler blends. Concerning concentrated polymer blends, a phase inversion mechanism induced by a simple shear was studied in polydimethylsiloxane-acqueous solution of hydroxypropylcellulose blends. The phase inversion was induced by a change of shear rate, due to viscosity ratio inversion. It is a long mechanism passing through different transient morphological stages. The effect of concentration, shear rate and elasticity on the duration of the transient flow and on the final morphology was investigated. The final morphology (phase inversion or refinement of the initial morphology) results from a competition between break-up and coalescence of the filaments of each component. Dispersion of carbon black agglomerates embedded in elastomers was also studied with a counter-rotating rheometer and with an internal mixer. Dispersion mechanisms of isolated agglomerates are different from what was previously observed in Newtonian matrices: higher critical shear stresses for dispersion, slower kinetics and new observed mechanisms (ribbon peeling and debonding). The cohesion of agglomerates is widely reinforced by the viscoelastic character of the impregnating matrix. Dispersion mechanisms directly depend on the level of impregnation of these agglomerates. Affecting both impregnation kinetics and debonding mechanisms, the wetting of the filler by the elastomer has an important impact on the dispersion mechanisms. Finally, these rheooptical observations do enable to explain some behaviors occurring during blending in a mixer.
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  • HAL Id : tel-00275370, version 1

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Marianne Astruc. Étude rhéo-optique des mécanismes de dispersion de mélanges sous cisaillement simple. 1 Mélanges concentrés de polymères immiscibles. 2 Mélanges polymères-charges poreuse. Mécanique [physics.med-ph]. École Nationale Supérieure des Mines de Paris, 2001. Français. ⟨NNT : 2001ENMP1014⟩. ⟨tel-00275370⟩

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