ADVANCES IN PREDICTION OF BLADE FORCES WITH VISCOELASTIC COATINGS, 2008 Advanced Coating Fundamentals Symposium

ARE YOU A TAPPI MEMBER? TAPPI members have exclusive, FREE access to technical conference papers and presentations six months after the conference in TAPPI's e-library. The e-Library offers:

• Unlimited access to more than 18,000+ documents
• Fast, robust search engine for fast search results
• Members get FREE access to conference proceedings, TAPPI JOURNAL articles, Paper360º articles, archived Solutions! articles, and much more
• View thousands of technical paper abstracts
• Ability to search by keyword, title, author, events or industry segment

*Technical papers and presentations are available for sale immediately following the conferences before the 6 month embargo period.

Please Note: This document will be available in PDF format in the "My Electronic Documents" link on the home page once your order has been completed. Please make sure you have the latest version of Acrobat Reader. Click on the Acrobat Reader icon to check for the latest version, it’s FREE. To print a hardcopy of a PDF file correctly you must have a postscript printer. If you are not sure if your printer is a postscript printer please refer to your owner’s manual.

Blade forces during the coating operation are related to the efficient and trouble free operation. Even though there has been much work reported on the topic blade coating of viscoelastic fluids, few quantitative comparisons between predicted and experimental blade forces have been published for paper coatings.

Experiments with a laboratory blade device with a known load are made for a series of coating formulations that have been characterized in terms of viscous and elastic properties. Purely viscous analysis of blade forces predicts coat weight-force relationships that are lower than those measured by a significant amount. Several viscoelastic constitutive equations were used in a commercial finite element code to predict blade forces. For all constitutive equations, increasing the elastic properties raised the blade force. However, even for a simple wedge geometry, converged solutions were not possible for significant elastic parameters, even after using various evolution techniques. Converged solutions were possible with the Geisekus model for parameters that were close to the correct steady shear rheology but low for the storage modulus; these force predictions were still lower than measured results. A method was developed to add the extra normal forces estimated by assuming a simple shear field to the full analysis with a Carreau model; results were the correct order as the experimental values.