Dissolution and growth of entrained bubbles when dip coating in a gas under reduced pressure

Benkreira, Hadj; Ikin, J.B.

doi:10.1016/j.ces.2010.07.017

Cited by 6 publications

(3 citation statements)

References 21 publications

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“…Specifically, the transient process of air entrainment (via the sawtooth meniscus) is not directly addressed by this study. Recent works have made advances in visualizing sawtooth-meniscus dynamics Benkreira & Ikin 2010) and providing a theoretical basis for air entrainment through free-surface cusps (Severtson & Aidun 1996;Eggers 2001; Eggers & Courrech du Pont 2009). Further progress requires thorough experimental characterization of high-speed interface behaviour.…”

Section: Resultsmentioning

confidence: 99%

Delaying the onset of dynamic wetting failure through meniscus confinement

2012

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Dynamic wetting is crucial to processes where liquid displaces another fluid along a solid surface, such as the deposition of a coating liquid onto a moving substrate. Numerous studies report the failure of dynamic wetting past some critical process speed. However, the hydrodynamic factors that influence the transition to wetting failure remain poorly understood from an empirical and theoretical perspective. The objective of this investigation is to determine the effect of meniscus confinement on the onset of dynamic wetting failure. A novel experimental system is designed to simultaneously view confined and unconfined wetting systems as they approach wetting failure. The experimental apparatus consists of a scraped steel roll that rotates into a bath of glycerol. Confinement is imposed via a gap formed between a coating die and the roll surface. Flow visualization is used to record the critical roll speed at which wetting failure occurs. Comparison of the confined and unconfined data shows a clear increase in the relative critical speed as the meniscus becomes more confined. A hydrodynamic model for wetting failure is developed and analysed with (i) lubrication theory and (ii) a two-dimensional finite-element method (FEM). Both approaches do a remarkable job of matching the observed confinement trend, but only the two-dimensional model yields accurate estimates of the absolute values of the critical speeds due to the highly two-dimensional nature of the stress field in the displacing liquid. The overall success of the hydrodynamic model suggests a wetting failure mechanism primarily related to viscous bending of the meniscus.

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Section: Resultsmentioning

confidence: 99%

Delaying the onset of dynamic wetting failure through meniscus confinement

2012

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“…Ruschak established a connection between the minimum wet film thickness, capillary number, slot gap, and dynamic contact angle . Higgins and Scriven incorporated viscosity effects into coating beads based on the research of Ruschak, and Benkreira and Khan − discovered that decreasing the ambient pressure from atmospheric to around 2 kPa increased the velocity of air entrainment. Lee et al demonstrated that reducing the coating gap in the slot die coating process allowed for faster substrate velocity prior to air entrainment using Newtonian solutions, and Huang et al proposed a new coating process that utilized the height difference between the upstream and downstream lips to reduce air entrainment and improve coating performance.…”

Section: Introductionmentioning

confidence: 99%

Bubble Defect Generation Mechanism in Slot Die Coating of High-Viscosity Fluids

Fang,

Yan,

et al. 2024

ACS Appl. Mater. Interfaces

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Slot die coating is a widely used technique for the production of high accuracy films. One of the main challenges in slot die coating processes is determining the optimal range of operating parameters to prevent defects, such as bubbles, in high-viscosity films. In this study, both simulation and experimental methods were used to investigate the changes in the upstream meniscus under various coating parameters. Two types of air entrainment processes were considered, dominated by fluid inertia and viscous force. The formation of anticlockwise and clockwise vortex flows near the bottom of the upstream meniscus was found to alter the apparent dynamic contact angle of the upstream meniscus, leading to fluctuations in the apparent dynamic contact angle within a range of 70°−75°to 135°−140°. These fluctuations eventually resulted in air entrainment. This research is important for improving the quality and efficiency of slot die coating processes.

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“…Coating with viscous liquids is usually present in very rich industrial trials, which allow the coating of particles under the shear forces exerted in a mixing device. A list of key investigations on peristaltic flows [22][23][24], multiphase flows [25][26][27][28][29], bubbly flows [30][31][32][33][34], coatings [35][36][37][38][39][40], elastic medium [41,42], and several other references are available, which provide a more in-depth understanding to the reader.…”

Section: Introductionmentioning

confidence: 99%

Buoyancy Driven Flow with Gas-Liquid Coatings of Peristaltic Bubbly Flow in Elastic Walls

et al. 2020

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In this paper, liquid coatings of bubbly flow with peristaltic motion inside elastic walls is investigated. The proposed model is constructed using the two-fluid approach with the most distinctive collaboration among gas, fluid, pressure, and drag forces. Variation in pressure leads to a change in void fraction. The differential controlling conditions affected by the long wavelength of the peristaltic wave and the slow movement are taken into account. Analytical results of the simplified governing equations are obtained using the homotopy perturbation method (HPM). The features of the significant parameters are shown and examined graphically.

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Dissolution and growth of entrained bubbles when dip coating in a gas under reduced pressure

Cited by 6 publications

References 21 publications

Delaying the onset of dynamic wetting failure through meniscus confinement

Delaying the onset of dynamic wetting failure through meniscus confinement

Bubble Defect Generation Mechanism in Slot Die Coating of High-Viscosity Fluids

Buoyancy Driven Flow with Gas-Liquid Coatings of Peristaltic Bubbly Flow in Elastic Walls

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