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首页> 外文学位 >Rheology of polymeric suspensions: Polymer nanocomposites and waterborne coatings.
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Rheology of polymeric suspensions: Polymer nanocomposites and waterborne coatings.

机译：聚合物悬浮液的流变学：聚合物纳米复合材料和水性涂料。

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The complexity inherited in the polymeric suspensions makes prediction and control of their rheological properties difficult. Much effort has been devoted to characterize these properties and considerable improvements have been made. However, much more work is desired in order to develop new products and understand the underlying knowledge about the flow behavior of the suspensions. In this work, the rheology of two types of polymeric suspensions, namely waterborne coatings and polymer/nanoclay and polymer carbon nanofibers has been studied.;As the waterborne coatings are non-Newtonian, the viscosity depends on the shear rate and the strain history, which makes the flow in circular pipes complicated. The rheology of a type of metallic automotive basecoat is measured using a highly accurate rheometer and the data is fitted to several constitutive models. The pressure drop of the paint flow in a straight circular pipe has been measured in a pilot plant, and the steady state laminar flow pressure drop over the pipe length has been calculated using numerical methods. Sisko model and Carreau model has been found to be able to predict the pressure drop accurately using the material parameters obtained from rheological measurements. The power law model is applicable for flows where the Reynolds number is less than 100. The effects of thixotropy can be neglected during normal continuous operation. The relatively higher initial pressure drop caused by the thixotropy of the paint occurs during start up is found to be 1.25 times the pressure drop at steady state. The paint studied shows abnormal temperature effects on the rheology. Steady shear viscosity decreases from 10 to 35 °C, and then increases at higher temperatures up to 45 °C.;In the study of the rheology of carbon nanofiber (CNF) suspensions in Newtonian fluids, it is found that the dispersion of the nanofibers determines the suspension rheology. The suspensions contain up to 5wt% CNFs. Steady shear viscosities of untreated sonicated suspensions are higher than that of better dispersed treated sonicated suspensions, due to the existence of large clumps and strong inter-particle interactions that block the flow. The measurements of small amplitude oscillatory shear and yield stress reveal that the both untreated sonicated and treated sonicated suspensions exhibit solid-like behavior when the nanofiber concentration is higher than 2wt%. Morphology investigations show that the acid treatment of the treated nanofibers disintegrates the agglomerates exists in the as-received CNFs and therefore improves dispersion, it also weaken them, as the subsequent sonication break most of the treated CNFs. (Abstract shortened by UMI.)
机译：聚合物悬浮液所继承的复杂性使得难以预测和控制其流变性。已经付出很多努力来表征这些性质，并且已经进行了相当大的改进。但是，为了开发新产品并了解有关悬浮液流动特性的基础知识，需要做更多的工作。在这项工作中，研究了两种类型的聚合物悬浮液的流变学，即水性涂料和聚合物/纳米粘土以及聚合物碳纳米纤维。由于水性涂料是非牛顿性的，因此粘度取决于剪切速率和应变历史，这使圆形管道中的流动变得复杂。使用高精度流变仪测量一种金属汽车底漆的流变学，并将数据拟合到多个本构模型。已经在中试工厂中测量了直管中的涂料流的压降，并已使用数值方法计算了整个管道长度上的稳态层流压降。发现Sisko模型和Carreau模型能够使用从流变测量获得的材料参数来准确预测压降。幂律模型适用于雷诺数小于100的流动。在正常的连续运行过程中，触变性的影响可以忽略。发现在启动过程中，由涂料的触变性引起的相对较高的初始压降为稳态压降的1.25倍。研究的涂料显示出异常的温度变化对流变学的影响。稳态剪切粘度从10降低到35°C，然后在更高的温度下升高到45°C .;在牛顿流体中碳纳米纤维（CNF）悬浮液的流变学研究中，发现纳米纤维的分散性确定悬浮液的流变性。悬浮液包含高达5wt％的CNF。由于存在大的团块和强烈的颗粒间相互作用阻碍流动，未处理的超声处理悬浮液的稳态剪切粘度高于分散较好的处理后的超声悬浮液。小振幅振荡剪切和屈服应力的测量结果表明，当纳米纤维浓度高于2wt％时，未处理的超声处理和处理后的超声处理的悬浮液均显示出类似固体的行为。形态学研究表明，对酸处理的纳米纤维的处理使团聚体崩解，而这种团聚体存在于接收到的CNF中，因此改善了分散性，也削弱了它们，因为随后的超声处理破坏了大多数CNF。 （摘要由UMI缩短。）

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