Date of Award

Spring 2-24-2022

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Carl P. Tripp

Second Committee Member

Douglas W. Bousfield

Third Committee Member

William M. Gramlich

Additional Committee Members

Barbara Cole

Mehdi Tajvidi

Abstract

A typical paper coating formulation contains anionically charged pigments and latex to provide a high-quality surface for printing. However, during application and drying, the latex can migrate to the surface or deep into the paper, resulting in weak coating layers or the need to use a high latex content to obtain the same strength properties. In this thesis, we have explored the introduction of cationically charged particles into the suspension as a way to reduce the amount of binder in the coatings, improve coating strength and reduce binder migration. With these aims in mind, we have generated cationic precipitated calcium carbonate and styrene-butadiene latex through adsorption of polyelectrolytes on their anionic counterparts and show that paper coatings, prepared using formulations of these cationic components, have higher coating strengths than coatings produced with conventional anionic formulations. While performing the charge reversal process, the particle size of the original anionic material is maintained. Furthermore, we show that cationic coating formulations can provide equal strength to the paper coatings at reduced binder levels. To reduce binder migration in the coatings, we explored using a mixed cationic-anionic formulation where an anionic latex binder is adsorbed on the surface of a cationic pigment to produce an overall anionic suspension. We show that latex-covered pigment suspensions have lower binder migration in paper coatings when compared to coatings produced with standard formulations. This is because the latex is fixed to the pigment and is not able to migrate independently from the pigment during the drying step. Building on the concept of mixed cationic/anionic particulate systems, we investigated its use to improve the dewatering of CNF/particulate suspensions. Specifically, we generated CNF/precipitated calcium carbonate (PCC) suspensions and show that the substitution of cationic PCC for traditional anionic PCC pigments leads to higher (up to 2.7 times) dewatering rates of the suspensions. The higher dewatering rate is shown to be the result of the adsorption of the anionic CNF on the cationic PCC particles. The resulting dry CNF/PCC films have Young’s moduli and tensile stress of up to 4 GPa and 60 MPa respectively. However, after being immersed in the water these films lost their mechanical properties Finally, to improve the water resistance of these films, we performed an acetylation reaction on the films using supercritical CO2 as the solvent.

Download

Share