SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Monday, April 13, 2020

1:00 PM

via

WebEx Video Conferencing

https://gatech.webex.com/gatech/j.php?MTID=mf394e73488b641d2427d5af732fe2086

will be held the

DISSERTATION  PROPOSAL DEFENSE

for

Nasreen Khan

"Increasing Solids into the Dryer in the Papermaking Process Via Rational Design of Polyelectrolyte Complexes"

Committee Members:

Prof. Blair Brettmann, Advisor, ChBE/MSE

Prof. Christopher Luettgen, RBI

Prof. Carson Meredith, RBI/ChBE

Prof. Paul Russo, MSE/CHEM

Prof. Meisha Shofner, MSE

Abstract:

The most energy intensive step in the paper manufacturing process is at the dryer. By increasing the percent solids of the wet paper web that enters the dryer, the sustainability and energy efficiency of the paper-making process can be improved. Polyelectrolytes and oppositely charged polyelectrolyte complexes (PECs) are commonly used to improve drainage and increase the flocculation of cellulose fibers, but the influence of polyelectrolyte characteristics such as pH dependency, hydrophobicity, and molecular architecture on their interactions with cellulose fibers are not well understood. In this thesis, I aim to determine how the selection of solid-like precipitate or liquid-like coacervate forming PECs enhances adsorption and association of the PECs to cellulose fibers and how this improves water retention and increases percent solids.

This work will specifically study the effects of mixing order and chemical structure of polyelectrolytes on the rate of assembly and association of PEC to cellulose. To do this, cellulose nanofibers are used as a “worst-case” fiber source because of their large surface area and propensity to retain water. Additionally, hemicelluloses will be used as models for β-D-glucose to further determine how the base chemical unit of cellulose interacts with PECs without surface area or porosity effects. The role of electrostatic and other molecular interactions on the morphological association of PECs and overall water content in the cellulose-PEC systems will be studied through electrophoretic mobility, microscopy, water retention value testing, gravimetric, calorimetric, and drainage testing techniques. Overall, I will develop design principles to select appropriate PECs to decrease water in the paper formulation entering the dryer while contributing to the fundamental understanding of how polyelectrolyte complexes interact with particles.