Wei Gu

Date of Award

12-2006

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Carl Tripp

Second Committee Member

Douglas Bousfield

Third Committee Member

Touradj Solouki

Abstract

Ink setting affects offset print quality issues such as print mottle and print gloss. It is known that ink setting depends on many factors, such as the nature of the substrate, the properties of the coating, and the ink formulation. However, the role of pigment surface chemistry in offset ink setting is unknown. From an experimental perspective, it is difficult to determine the role of the surface chemistry as it requires paper coatings that are similar in physical properties and differ only in the pigment surface chemistry. The aim of this study was two-fold. The first was to apply methods such as atomic layer deposition (ALD), sol-gel deposition, and silane treatment to modify pigment surface chemistry and evaluate the coating properties before and after modification. The second aim was to gain an understanding of the role of pigment surface chemistry in offset ink setting. This thesis is organized into six chapters and an appendix. Chapter 1 provides an overview and background of paper coatings and pigment modification chemistries. Chapter 2 describes the experimental procedures and equipment common to all work described in chapters 3-6. In chapter 3, ALD deposition of TiO2 on SiO2 powder was investigated using infrared spectroscopy. The work of this chapter identified the role of water in the reaction process and its importance in controlling the layer-by-layer growth rate on pigments. In chapter 4, infrared spectroscopy was used to investigate the reaction of silanes with TiO2 and Al2O3 using SC-CO2 as a solvent. The work of chapter 4 showed that caution must be exercised when using sc-CO2 as the solvent in the surface treatment of oxides other than silica. In chapter 5, a novel method to obtain a high conversion of Ca(OH)2 powder to CaCO3 is described. The work of modification of pigment surface chemistry and the study of its role in determining offset ink setting is described in chapter 6. Using sc-CO2 as solvent for silane post-treatment, two coatings with similar physical properties but differ in surface chemistry was obtained. This enabled us to determine the role of pigments surface chemistry in offset ink setting.

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