Shear and extensional viscosity characteristics of a series of hydrophobically associating polyelectrolytes
Shear and extensional viscosity characteristics of a series of hydrophobically associating polyelectrolytes
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一系列疏水缔合聚电解质的剪切和拉伸粘度特性
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
Peter A. Williams
中科院分区：
文献类型：
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作者：
J. Kennedy;J. Meadows;Peter A. Williams
研究和比较了一系列疏水缔合聚电解质水溶液的剪切和拉伸粘度特性。所研究的聚合物包括甲基丙烯酸/丙烯酸乙酯共聚物骨架，其中含有不同水平的垂链C18疏水剂（0-2 mol%）。所有溶液的拉伸黏度均高于其对应的剪切黏度，在低应变率下，计算的Trouton比趋于预测值3，此后随拉伸应变率的增大而增大。在两种流动模式下，溶液的粘度随聚合物浓度和疏水含量的增加而增加。与在剪切流动中观察到的聚合物溶液的纯粹剪切变薄特性相反，发现许多体系的拉伸粘度-应变速率曲线包含一个初始应变增厚区域，尽管在较高应变速率下观察到应变变薄行为。对于任何给定的体系，拉伸粘度出现明显最大值时的应变速率随着聚合物浓度的增加而降低。在已知会破坏分子间疏水缔合区域的添加剂（如过量的表面活性剂或可混溶的酒精非溶剂）的存在下，发现缔合型聚电解质的典型溶液的拉伸粘度显著降低，并且在粘度-应变率谱中不再表现出最大值。
The shear and extensional viscosity characteristics of aqueous solutions of a series of hydrophobically associating polyelectrolytes have been investigated and compared. The polymers studied consisted of a methacrylic acid/ethyl acrylate copolymer backbone containing varying levels of incorporation (0–2 mol%) of a pendant C18 hydrophobe. The extensional viscosities of all solutions were found to be higher than their corresponding shear viscosities, with the calculated Trouton ratio tending towards the predicted value of three at low strain rates but increasing with increasing extensional strain rate thereafter. In both flow modes, the viscosities of the solutions increased with increasing concentration and hydrophobe content of the polymers. In contrast to the purely shear-thinning characteristics of the polymer solutions observed in shear flow, the extensional viscosity–strain rate profiles of a number of systems were found to contain an initial region of strain-thickening, although strain-thinning behaviour was observed at higher strain rates. For any given system, the strain rate at which the evident maxima in extensional viscosity occurred decreased with increasing polymer concentration. In the presence of additives such as excess surfactant or a miscible alcoholic non-solvent, which are known to disrupt regions of intermolecular hydrophobic associations, the extensional viscosity of a typical solution of an associative polyelectrolyte was found to be significantly reduced and no longer to exhibit a maximum in the viscosity–strain rate profile.