Air Entrainment in Thin Liquid Film Coating Operations PDF Download

Author: Mohammad Ilyas Khan
Publisher:
ISBN: 9783659924149
Category :
Languages : en
Pages : 176

View

Book Description

Author: P.M. Schweizer
Publisher: Springer Science & Business Media
ISBN: 9401153426
Category : Science
Languages : en
Pages : 794

View

Book Description
This multi-authored volume provides a comprehensive and in-depth account of the highly interdisciplinary science and technology of liquid film coating. The book covers fundamental principles from a wide range of scientific disciplines, including fluid mechanics aand transport phenomena, capillary hydrodynamics, surface and colloid science. The authors, all acknowledged eperts in their fields, represent a balance between industrial and academic points of view. Throughout the text, many case studies illustrate how scientific principles together with advanced experimental and theoretical methods are applied to develop and optimize manufacturing processes of eve increasing sophiatication and efficiency. In the first part of the book, the authors systematically recount the underlying physical principles and important material properties. The second part of the book gives a comprehensive overview of the most advanced experimental, mathematical and computational methods available today to investigate coating processes. The third part provides an overview and critical literature review for all major classes of liquid film coating processes of industrial importance.

Author: H. Benkreira
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 232

View

Book Description
This review is essential reading for those involved in the research, development and design of coating flows, rheology, drying, and solvent recovery.

Author: J-M. Buchlin
Publisher:
ISBN:
Category : Coating processes
Languages : en
Pages : 524

View

Book Description

Author: Min Young Pack
Publisher:
ISBN:
Category : Fluid mechanics
Languages : en
Pages : 176

View

Book Description
Drop impact is fundamental to various natural and industrial processes such as rain-induced soil erosion and spray coating technologies. The recent discovery of the role of the air entrainment between the droplet and impacting surface has produced numerous works uncovering the unique physics that correlates the micro-scale and nano-scale spatio-temporal dynamics to the macro-scale impact outcomes such as droplets bouncing on thin air films no thicker than a few microns. In this work, the macroscopic droplet morphologies under impacting conditions are juxtaposed with the microscopic behavior of the air film underneath the droplet where an interplay of various forces - inertial, viscous, capillary and intermolecular forces - coexist and dictate the final outcomes of the impacting drop. Lubricant infused surfaces (LIS) have recently been studied due to their potential benefit in various applications such as pressure-stable, self-healing, ice- and liquid-repellent materials. Combining the techniques of total internal reflection microscopy and reflection interference microscopy, we examine the dynamics of an underlying air film upon drop impact on lubricated substrates where the thin liquid film is immiscible to the drop. In contrast to drop impact on solid surfaces where even the smallest asperities cause random breakup of the entraining air film, we report two air film failure mechanisms on lubricated surfaces. In particular, using 9́8 5 ℗æm thick liquid films of high viscosity, which should make the substrate nearly atomically smooth, we show that air film rupture shifts from asperity-driven to a controlled event. At low Weber numbers (We

Author: Philip H Gaskell
Publisher: World Scientific
ISBN: 9814602582
Category :
Languages : en
Pages : 426

View

Book Description
This volume contains three keynote presentations, given by experts in the field of experimental methods, rheology and the modeling of coating dies. Included also are 40 contributions drawn from the following areas of coating research and application: instability and coating defects; surface treatment; spreading and leveling; experimental investigations; surface tension and gravity driven flows; roll and gravure coating; rheological effects in coating processes.As such, these proceedings should prove a valuable resource for both researchers and coating practitioners.

Author: Mansour Masoud Elgadafi
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
In all coating applications, a liquid film displaces air in contact with a dry solid substrate. At a low substrate speed a thin uniform wetting line is formed on the substrates surface, but at a high speed the wetting line becomes segmented and unsteady as air becomes entrained between the substrate and the liquid. These air bubbles affect the quality of the coated product and any means to postpone this at higher speeds without changing the specifications of the coating liquid is desirable. This research assesses the validity of a theoretically based concept developed by Blake and Rushack [1] and exploited by Cohu and Benkreira [2] for dip coating. The concept suggests that angling the wetting line by an angle ß would increase the speed at which air is entrained by a factor 1/cos ß. In practice, if achieved this is a significant increase that would result in more economical operation. This concept was tested in a fast coating operation that of curtain coating which is already enhanced by what is known as hydrodynamic assistance [2]. Here we are effectively checking an additional assistance to wetting. The work, performed on a purposed built curtain coater and a rotating die, with a range of fluids showed the concept to hold but provided the data are processed in a way that separate the effect of curtain impingement from the slanting of the wetting line.

Author: Xingyi Shi
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
We encounter thin liquid films on a daily basis. The micron-thick tear film coating the cornea ensures the clarity of our vision. Pulmonary surfactants coating the air-liquid interface in the alveoli enable us to breath. Lubricant foaming in a gear box can lead to machine degradation and unsafe operations. Textile dye solution films drying unevenly can leave undesirable marks on the fabric. A fundamental understanding of thin liquid film stability is key to optimizing the compositions of the base liquid to suit our needs and applications. In this research, we examine the effects of liquid composition and substrate materials on the dynamics of thin liquid films by building heat and mass transfer models and conducting interferometric experiments via the dynamic fluid-film interferometer. The geometry of a thin liquid film dictates that the liquid-air interactions are critical in affecting the dynamics of the films. Many such interactions can lead to an uneven distribution of surface tension, creating Marangoni flow. The interplay between the Marangoni flow and other physical forces such as capillarity and gravity govern the dynamics of most thin liquid films. A key part of the work focuses on one of the simplest systems that captures all of the major physical forces at play in a thin liquid film: evaporating binary silicone oil films over a glass dome or an air bubble. The binary silicone oil composes of two silicone oils with different viscosity, surface tension, and evaporation rate. Evaporation and the curvature of the substrates create a thin film with varying thickness and composition, thereby surface tension. In the experimental system, a thin film is formed by forcing the curved substrate upward until the apex of the substrate penetrates the initially flat air/liquid interface. The forcing is then stopped and the evolution of the film is recorded by a camera positioned directly above the thin film. Combining experimental observations and theoretical modeling, we elucidate the mechanisms behind the resulting dramatic thin film dynamics. For a binary silicone oil film over a glass dome, at low volume fractions of the less evaporative species ( 0.3%), the liquid film remains axisymmetric and is stabilized by van der Waals interactions and Marangoni flows [1]. At higher concentrations ( 0.35%), the increase in Marangoni flow leads to a film that is more susceptible to ambient disturbances, resulting in asymmetry breakage events [2]. Faster dynamics are observed for an oil film over an air bubble, due to the reduction in resistance to flow. At low volume fractions of the more evaporative species (

Author: Peter M. Schweizer
Publisher: Springer Nature
ISBN: 3031041801
Category : Technology & Engineering
Languages : en
Pages : 691

View

Book Description
This book compares premetered methods to self-metered processes and addresses general properties of premetered methods. It presents specific properties of slot, slide, and curtain coating. The book is divided in three parts: Part I compares premetered methods to self-metered processes. It explains the term “premetered,” which is an expression of the law of mass conservation, and discusses the physical fluid properties that are relevant for premetered processes. Furthermore, it presents in detail the various basic flow fields that make up premetered coating methods. Lastly, it introduces the concepts of wall shear stress, residence time, and hydrodynamic assist to dynamic wetting. Part II addresses general properties of premetered methods, such as the fluid conditioning and delivery systems, the nominal film thickness, and the film thickness uniformity, both in machine and cross-web directions (die design). It lists the attractive features of simultaneous multilayer applications, including an explanation of how mixing of adjacent layers can be prevented. This section concludes by revisiting examples of economic considerations. Part III presents specific properties of slot, slide, and curtain coating. It examines various topics, such as coating equipment and coating configurations, coating modes, details of the various flow fields, operating window and process limitations, and process optimization.

Author: Ashutosh Sharma
Publisher: Alpha Science Int'l Ltd.
ISBN:
Category : Science
Languages : en
Pages : 532

View

Book Description
Contributed papers presented at a seminar held during September 1-4, 2006.