Manoj P, Watson AD, Hibberd DJ, Fillery-Travis AJ, Robins MM
Institute of Food Research, Norwich Research Park, Norwich, Norfolk, NR4 7UA, United Kingdom
J Colloid Interface Sci. 1998 Nov 15;207(2):294-302. doi: 10.1006/jcis.1998.5802.
Depletion flocculation of an alkane-in-water emulsion has previously been found to induce phase separation and, above certain polymer and oil concentrations, a delay period prior to the onset of creaming. In this paper the steady-state viscometry of an emulsion of 1-bromohexadecane-in-water has been investigated in the presence of hydroxyethylcellulose as the depletion flocculant. We have sought to characterize the flow behavior of this emulsion system and determine the characteristic rheology during the delay period. The use of this near-density-matched system eliminates the effect of creaming, and we have, therefore, characterized the delay period by reference to the behavior of a related system, differing only in oil composition. At oil and polymer concentrations conducive to the presence of a delay period, the emulsions were found to be shear thinning, whereas the emulsion system in the absence of polymer and the isolated continuous phases were Newtonian. The structure formation influencing the rheology of the emulsions at high polymer concentrations was attributed entirely to interdroplet depletion interactions. The concept of dynamic yield stress for such a system is discussed and the consequences for the structure of a buoyancy-resisting space-spanning phase or "transient gel." Copyright 1998 Academic Press.
先前已发现水包烷乳液的耗尽絮凝会引发相分离，并且在特定的聚合物和油浓度以上，会出现一个在乳析开始之前的延迟期。在本文中，研究了在作为耗尽絮凝剂的羟乙基纤维素存在下，1-溴十六烷水包乳液的稳态粘度。我们试图表征该乳液体系的流动行为，并确定延迟期内的特征流变学。使用这种近密度匹配体系消除了乳析的影响，因此，我们通过参考仅在油组成上有所不同的相关体系的行为来表征延迟期。在有利于延迟期存在的油和聚合物浓度下，发现乳液呈剪切变稀，而在没有聚合物的乳液体系和分离出的连续相中则呈牛顿流体性质。在高聚合物浓度下影响乳液流变学的结构形成完全归因于液滴间的耗尽相互作用。讨论了这种体系的动态屈服应力概念以及对抗浮力的空间跨越相或“瞬态凝胶”结构的影响。版权所有1998年学术出版社。
