Mechanistic aspects of nanocellulose–cationic starch–colloidal silica systems for papermaking, TAPPI Journal February 2023

Application: Process optimization of chemical additives systems in paper mills are often evolutionary in nature, based on observations during papermaking. This article highlights aspects that merit inclusion in laboratory tests and commercial paper machine trials when the goal is to achieve strength benefits by the addition of NFC at the wet end.

Author: Nelson A. Barrios, Larden J. Garland, Brandon D. Leib, and Martin A. Hubbe

ABSTRACT: Optimization of a chemical additive program for a paper machine can require attention to both colloidal charges and kinetic effects. This work considered an additive program with two negatively charged substances (nanofibrillated cellulose [NFC] and colloidal silica) and two positively charged items (cationic starch and cationic acrylamide copolymer retention aid). Results were shown to depend on charge interactions; however, that clearly was not the whole story. Some findings related to cationic demand, dewatering, fine-particle retention, and flocculation among fibers were best explained in terms of at least partly irreversible complexation interactions between the charged entities. Adjustments in ratios between oppositely charged additives, their sequences of addition, and effects of hydrodynamic shear levels all affected the results. In general, the most promising results were obtained at a cationic starch level of 0.25% to 0.5% based on sheet solids in systems where the cationic starch was used as a pretreatment for NFC.