Loading...
Fluid Mechanics of High Speed Deformable Roll coating. An experimental and theoretical study of film thickness and stability in high speed deformable roll coating flow with Newtonian and non-Newtonian liquids
Sarma, Sreedhara
Sarma, Sreedhara
Publication Date
2015
End of Embargo
Supervisor
Rights
The University of Bradford theses are licenced under a Creative Commons Licence.
Peer-Reviewed
Open Access status
Accepted for publication
Institution
University of Bradford
Department
Faculty of Engineering and Informatics
Awarded
2015
Embargo end date
Collections
Additional title
Abstract
High operation speeds and thin coating films are desirable in many industrial applications. But the quality of the product, which is primarily determined by an optimum process window, is affected by non-uniformities and instabilities originating at higher operation speeds.
Unlike other academic works, because of associated industrial relevance, particular attention was given towards the use of industrially relevant coating systems or generation of model fluids, which replicate the real coating solutions. One of the novelties of the research proposed lie in an integrated approach, utilising a range of comparative rheometrical techniques, with a focus on measurement of: (i) high strain rate shear viscosity [η], (ii) high strain rate uniaxial extensional viscosity [ηE] (iii) high strain rate elasticity (N1).
Deformable roll coating, in terms of classification, is the ultimate metered coating flow. The flow is controlled by the combination of hydrodynamic force and elastic deformation effect, which could be complicated by the presence of non-Newtonian fluid. This study necessitated the design and construction of a sophisticated deformable coating rig with the ability to operate over a wide range of conditions. Although the irregularities and instabilities associated with the roller coating process
has been studied previously, the concerned speeds of operation in this study is around three times higher.
The main objectives of this study was to carry out a comprehensive experimental programme establishing relationship exist between film thickness, film quality and operating parameters. Main identified operating parameters are roll speeds, roll gaps or applied load between the rolls, the elasticity with thickness of elastomeric layer and different rheological properties of the coating fluids. Surface instabilities and air entrainment are identified as the major limitations to being able to coat at higher speeds.
Version
Citation
Link to publisher’s version
Link to published version
Link to Version of Record
Type
Thesis
Qualification name
PhD
Notes
The full text was made available at the end of the embargo, 1st July 2020