The Stability of Multi-Layer Curtain Coating

Henry, Dominic James Dougal (2016). The Stability of Multi-Layer Curtain Coating. University of Birmingham. Ph.D.

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Abstract

Coating flows have a vast array of applications, whereby a thin liquid film coats the surface of a solid substrate. Curtain coating is a lucrative method due to being able to coat multiple layers at the same time in one process. Combining many different components of fluid mechanics into one industrial process, fully understanding all the mechanisms involved in curtain coating is essential to fully utilise its potential of efficiently and uniformly coating multiple layers simultaneously. This thesis considers two of these components; film flow along an inclined plane and the stability of a liquid curtain, including both during and after curtain break-up, combining experimental and theoretical studies. An experimental investigation of the flow down the inclined plane of the coating die is presented, for a wide range of physical properties and parameters, with the results compared to a simple mathematical model derived from multi-layered film flow along an inclined surface. Furthermore, a mathematical model of a free-falling surfactant laden liquid curtain under gravity is derived. Incorporating the effect of an insoluble surfactant is found to alter steady state profiles, as well as stabilizing the curtain to small perturbations about the steady state. An experimental study into the liquid curtain during break-up is then presented, investigating the hysteresis phenomenon of curtain stability, as well as the origins of break-up and the speed of sheet retraction. Finally, a mathematical model of the spacing between the array of liquid jets that is formed after the curtain disintegrates is developed.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):