Lateral drying in thick films of waterborne colloidal particles
Lateral drying in thick films of waterborne colloidal particles
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DOI：
10.1021/la001590h
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发表时间：
2001-05-29
期刊：
影响因子：
3.9
通讯作者：
Keddie, JL
中科院分区：
文献类型：
--
作者：
Salamanca, JM;Ciampi, E;Keddie, JL
本文首次系统定量地研究了影响胶体膜横向干燥的因素。直到水从干燥的水性胶体分散体的厚膜边缘退去的时间，称为开口。时间，被测量为几个可控参数的函数。磁共振显微镜使用一种特殊设计的探针，无创地提供了水浓度的直接和定量测量，作为垂直和横向位置的函数。从已知厚度、粒径和表面张力值的晶格干燥膜中获得图像，这些图像整齐地封装在毛细管压力减小的表达式中，p，。在相对较窄的p(c)值范围内，发现打开时间的强烈增加。较大的颗粒，较慢的蒸发速率，和较薄的薄膜鼓励更均匀的横向干燥与延迟从边缘干燥。这一观察结果与最近基于润滑近似的模型（Routh, a， F.; Russel， W. B. AIChE j . 1998,44, 2088）一致。实验和建模指出了一种控制水性胶体横向干燥过程的方法。
The first systematic and quantitative experimental study of the influences on lateral drying in colloidal films is reported. The time until water recedes from the edge of a drying thick film of a waterborne colloidal dispersion, called the open. time, was measured as a function of several controllable parameters. Magnetic resonance microscopy, using a specially designed probe, noninvasively provides a direct and quantitative measurement of the concentration of water as a function of vertical and lateral position. Images were obtained from drying films of latices with known values of thickness, particle size, and surface tension, which are neatly encapsulated in an expression for the reduced capillary pressure, p,. A strong increase in the open time was found over a relatively narrow range of p(c) values. Larger particles, slower evaporation rates, and thinner films encourage more uniform lateral drying with a delay in drying from the edges. This observation is consistent with a recent model (Routh, A, F.; Russel, W. B. AIChE J.1998, 44, 2088) based on the lubrication approximation. The experiments and the modeling point to a way of achieving control over the lateral drying processes of waterborne colloids.