MINIMUM WET THICKNESS IN EXTRUSION SLOT COATING
MINIMUM WET THICKNESS IN EXTRUSION SLOT COATING
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DOI：
10.1016/0009-2509(92)85018-7
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发表时间：
1992-05-01
影响因子：
4.7
通讯作者：
LIU, TJ
中科院分区：
文献类型：
--
作者：
LEE, KY;LIU, LD;LIU, TJ
对挤出狭缝涂布的最小湿厚度进行了实验研究。 结果表明，在实验条件范围内，牛顿溶液存在一个临界毛细管数Ca ~*，低于Ca ~* 时，最小润湿厚度强烈地依赖于涂布速度和流体粘度，即毛细管数Ca。 在Ca* 以上，最小湿厚度与毛细管数无关，并且仅是涂层间隙的函数。 与滑动涂布法相比，当Ca < Ca* 时，两种涂布法的最小湿厚度非常接近。当Ca > Ca* 时，挤出狭缝涂布的最小湿厚度随毛细管数的增加而趋于恒定，无量纲最小湿厚度也趋于恒定，而滑动涂布的最小湿厚度随毛细管数的增加而增加。 实验确定的最小湿厚度挤压槽涂层已与Ruschak的理论预测，希金斯和Scriven。 研究了微珠真空度的影响，发现微珠真空度的提高可以有效地降低最小润湿厚度，特别是在流体粘度较低和涂层间隙较窄的情况下。
An experimental study has been carried out to determine the minimum wet thickness of extrusion slot coating. It was found that there exists a critical capillary number Ca* for Newtonian solutions within the range of experimental conditions; below Ca*, the minimum wet thickness depends strongly on the coating speed and the fluid viscosity, or the capillary number Ca. Above Ca*, the minimum wet thickness is independent of the capillary number and is a function of the coating gap only. Comparing with slide coating, we have found that the minimum wet thickness for both coating methods are very close if Ca < Ca*. As Ca > Ca*, the minimum wet thickness for extrusion slot coating will become constant as the capillary number increases and the dimensionless minimum wet thickness will reach a constant value, but the minimum wet thickness for slide coating will increase as the capillary number increases. The experimentally determined minimum wet thickness for extrusion slot coating has been compared with the theoretical predictions of Ruschak, and of Higgins and Scriven. The effect of bead vacuum was also investigated, it was found that increasing bead vacuum can effectively reduce the minimum wet thickness particularly if the fluid viscosity is low and the coating gap is narrow.