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Poster De Conférence Année : 2015

Bubbles stability in a yield stress fluid

Résumé

Housing sector is the main source of energy consumption. Mineral foams are relevant and form an alternative insulating partial load-bearing building products. The calcium sulfate (an eco-friendly binder) foams containing a large amount of trapped bubbles are obtained by mixing of water, mineral binder and surfactants. The mix-then-foam process is then applied before the setting of the mineral matrix. To study the interaction between bubbles behavior and rheological properties evolution of the concentrated suspension, a transparent model fluid (dispersion of Carbopol® 676 in water) is used. Bubbles are injected using a variable volume syringe. Air pressure is controlled during injection. The air bubbles stability in yield stress polymer is analyzed by picture processing. The study of single bubble is first investigated in Carbopol® gels with various yield stresses, to model the effect of rheological properties evolution (setting effect of the binder). As expected, bubbles sizes and internal pressure evolve according to thermodynamic laws. During injection, bubble growing depends on various parameters: yield stress, injected air volume, pressure, bubble sphericity... The experiments lead to the identification of rheological behavior linking pressure, bubble geometry and yield stress in static condition. A modification of the Laplace law depending on yield stress of the fluid and bubble sphericity is proposed. The foam stability is mostly conditioned by coalescence phenomena. It consists on the fusion of two bubbles in contact after the separating membrane destruction. Experiments reveal that a small amount of surfactants promote the stability of the foam structure. The shape of bubbles after coalescence is strongly influenced by yield stress. The type and the surfactants amount generate a wide range of configuration. Results lead to a better understanding of the foams stability at fresh state. A chemical optimization regarding to mechanical and thermal properties targets is available.
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Dates et versions

hal-01169065 , version 1 (26-06-2015)

Identifiants

  • HAL Id : hal-01169065 , version 1

Citer

Gabriel Samson, Annabelle Phelipot-Mardelé, Christophe Lanos. Bubbles stability in a yield stress fluid. 10th annual european rheology conference, Apr 2015, Nantes, France. 2015. ⟨hal-01169065⟩
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