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Candidate:
Burak Aksoy
Degree
of: Doctor of Philosophy
Department: Paper Engineering, Chemical Engineering, and Imaging
Title: Effect of Coating Additives on the Rheological and Optical Properties of Coated Papers
Date: Tuesday, August 3, 2004 10:00-12:00 p.m.
B231 Parkview Campus
Committee:
Dr. Margaret K. Joyce, Chair
Dr. Paul D. Fleming
Dr. Abhay Sharma
Dr. Molly Williams
Abstract:
Although additives are used in small amounts (below 2wt.% of the total solids) in a coating formulation, they play an important role in the runnability and end-use performance of the coating. Among coating additives, the use of insolubilizers and fluorescent whitening agents (FWA's) has increased due to the increase in demand for higher quality graphic papers and packaging. Zirconium containing insolubilizers were studied for their rheological effects and silica ink-jet coatings. Both zirconium species had an influence on the rheological properties of the coating and its components. The interactions between the zirconium salts and the coating were found to be weak and lessened as the shear rate increased. In addition, fluorescent whitening agents were investigated for their optical effects on different grades of papers. Studies in FWA's included a thorough evaluation of optical measurement techniques and whiteness formulas, instrument, illumination conditions and paper grade effects on the optical measurements. The results showed several deficiencies in the current measurement techniques for assessment of brightness and whiteness of different grade papers and coatings containing FWA's and dyes. Most Whiteness formulae used today assess a sample relatively as to whiter, lighter and bluer. The results showed that when these formulas are applied
to colored samples they are generally unsuccessful in assessing tinted samples with chromaticities placed on the borders of white colors. New formulas expressing whiteness are proposed. These are compared with CIE, Hunter and Ganz whiteness formulas and TAPPI brightness through perceptual evaluation and instrumental measurements and analyses. Proposed formulas matched better with randomly selected observer assessments than the CIE, Hunter and Ganz whiteness formulas.
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