Oscillatory rheology of aqueous foams: surfactant, liquid fraction, experimental protocol and aging effects
Oscillatory rheology of aqueous foams: surfactant, liquid fraction, experimental protocol and aging effects
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DOI：
10.1039/b817543h
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发表时间：
2009-01-01
期刊：
影响因子：
3.4
通讯作者：
Saint-Jalmes, A.
中科院分区：
文献类型：
--
作者：
Marze, S.;Guillermic, R. M.;Saint-Jalmes, A.
我们报告了一组关于良好控制的水性泡沫的新流变数据。我们研究并分析了线性粘弹性状态、泡沫屈服和高于屈服的非线性状态实际上如何取决于界面特性、气泡尺寸、液体分数和泡沫年龄。结果与之前的泡沫和乳液研究以及模型进行了比较。粘弹性线性特性和屈服应力强烈依赖于液体分数，并且对于低分子量表面活性剂，提供“流体状”界面，恢复了普遍的行为。然而，观察到蛋白质泡沫的差异，并讨论了与界面和薄膜特性相关的问题。我们还讨论了屈服应力以上非线性区域的特征，这不能用最近的模型完全解释。随着泡沫老化，粘弹性特性的演变可以用泡沫排水和然而，我们还提出了一种新模式的振荡实验的结果，在恒定剪切速率下，用这种新协议获得的宏观结果与气泡尺度的微观测量结果惊人地相关，然后我们表明，通过应用变形或泡沫粗化可以获得相同的固液转变；我们提出，转变是由德博拉数 De 控制的，Deborah 数可以被视为频率比或变形比。 < 1，泡沫呈流体状，气泡无堵塞（De > 1 时则相反）。
We report a new set of rheological data on well controlled aqueous foams. We investigate and analyze how the linear viscoelastic regime, the foam yielding and the non-linear regimes above yielding actually depends on the interfacial properties, bubble size, liquid fraction and foam age. Results are compared to previous works on foams and emulsions, and to models. The viscoelastic linear properties and yield stress are strongly dependent on the liquid fraction, and for a low molecular weight surfactant, providing "fluid-like'' interfaces, a universal behavior is recovered. However, discrepancies are observed for protein foams, and are discussed in relation to the interface and thin film properties. We also discuss the features of the non linear regimes above the yield stress, which cannot be fully explained by recent models. As the foam ages, the evolution of the viscoelastic properties can be interpreted in terms of foam drainage and coarsening; nevertheless, some of the aging effects remain unexplained. We also present the results of a new mode of oscillatory experiments, at constant shear rate the macroscopic results obtained with this new protocol turn out to be strikingly well correlated to microscopic measurements at the bubble scale. We then show that a same solid-liquid transition is obtained either by applying a deformation, or by the foam coarsening; we propose that the transition is controlled by a Deborah number De, which can be seen either as a frequency ratio or a deformation ratio. For De < 1, the foam is fluid-like and the bubbles are unjammed (and the opposite is true when De > 1).