Numerical analysis of slot die coating of nanocellulosic materialsShow others and affiliations
2020 (English)In: TAPPI Journal, ISSN 0734-1415, Vol. 19, no 11, p. 575-582Article in journal (Refereed) Published
Abstract [en]
Nanocellulosic coatings as a food packaging material are of commercial interest due to their nontox-ic nature, renewability, and excellent barrier properties. Complex shear-thinning rheology poses challenges in designing and sizing equipment to pump, mix, and process the suspension and actual coating process. This study aims to determine the effectiveness of computational fluid dynamics (CFD) in predicting nanocellulosic suspension flow in light of existing rheological data. We employ and compare three distinct rheological models to characterize the rheology and flow of nanocellulose suspensions through a slot die coater, where the model parameters are established from existing slot rheometry measurements. A volume-of-fluid (VoF) based finite volume method is employed to simulate the flow in a slot die operated in an unconventional metering mode. Results with the Casson model predict the presence of unyielded regions in the flow, which was not captured using the power law model. These stagnation regions will incur coatability issues stemming from flow intermittencies and lead to poten-tial defects in the coating layer, including fracture. The results suggest that a rheological model that includes yield stress should be considered while modeling such flows. A need for better rheological data to model nanocellulosic flows, especially at high consistencies and shear rates, is also highlighted. Application: This work identifies and clarifies the challenges to be addressed when considering industrial scale nanocellulose coating of paperboard.
Place, publisher, year, edition, pages
TAPPI Press, 2020. Vol. 19, no 11, p. 575-582
Keywords [en]
Cellulose, Cellulose nanocrystals, Coatings, Computational fluid dynamics, Elasticity, Finite volume method, Nanocellulose, Packaging materials, Shear flow, Shear thinning, Yield stress, Barrier properties, Food-packaging materials, Rheological modeling, Rheological models, Rheometry measurement, Shear-thinning rheology, Slot-die coatings, Stagnation regions, Suspensions (fluids)
National Category
Mechanical Engineering Chemical Sciences
Research subject
Chemical Engineering
Identifiers
URN: urn:nbn:se:kau:diva-83112DOI: 10.32964/TJ19.11.575ISI: 000595531400002Scopus ID: 2-s2.0-85097071287OAI: oai:DiVA.org:kau-83112DiVA, id: diva2:1530084
2021-02-212021-02-212021-11-26Bibliographically approved