Paper Number
SC29 

Session
Suspensions, Colloids and Granular Systems

Title
Yield stress and structure recovery of flocculated micro and nanofibrillated cellulose (MNFC) suspensions

Presentation Date and Time
October 11, 2017 (Wednesday) 2:20

Track / Room
Track 3 / Crystal C

Authors (Click on name to view author profile)

1. Facchine, Emily G. (North Carolina State University, Chemical and Biomolecular Engineering)
2. Ghosh, Koushik (Eastman)
3. Vargantwar, Pruthesh (Eastman)
4. Spontak, Richard J. (North Carolina State University, Chemical and Biomolecular Engineering)
5. Rojas, Orlando J. (North Carolina State University, Chemical and Biomolecular Engineering)
6. Khan, Saad A. (North Carolina State University, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Emily G. Facchine¹, Koushik Ghosh², Pruthesh Vargantwar², Richard J. Spontak¹, Orlando J. Rojas¹, and Saad A. Khan^1
1Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC; ²Eastman, Kingsport, TN

Speaker / Presenter 
Facchine, Emily G.

Text of Abstract
Aqueous suspensions of micro and nanofibrillated cellulose (MNFC) are known to exhibit gel-like behavior even at low concentrations. In this work, they were studied to determine their apparent yield stress and structure recovery behavior. Yield stress measurements were found to be highly susceptible to wall slip and shear banding, which can be mitigated somewhat by the use of serrated geometries. Yield stress values obtained by oscillatory and steady shear stress sweep were compared, and the effect of geometry on each method was evaluated. Experimental parameters such as the stress sweep frequency were found to have dramatic effects on the apparent yield behavior. Additionally, the microstructure recovery of the gel-like suspensions after breakdown was evaluated via oscillatory time sweeps under different conditions. These experiments demonstrated that the applied level of stress during structure breakdown has a pronounced effect on the extent of recovery of the gel structure, with a minimum recovery window observed at intermediate stress values in the range of the apparent yield stress. The observations are consistent with the presence of a network structure composed of interconnected flocs.