Exploring the gelation of aqueous cellulose nanocrystals (CNCs)-hydroxyethyl cellulose (HEC) mixtures

Jonathan Stolz,Zahra Khalili,Hale Oguzlu,Yaman Boluk,Hale Oguzlu

doi:10.1007/s00397-021-01285-1

Jonathan Stolz, Zahra Khalili + Show 3 more

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https://doi.org/10.1007/s00397-021-01285-1

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Journal: Rheologica acta	Publication Date: Jul 7, 2021
Citations: 12	License type: open-access

Affiliation: University of Alberta

Abstract

We investigated the gelation and microstructure of cellulose nanocrystals (CNCs) in nonionic hydroxyethyl cellulose (HEC) solutions. Cellulose nanocrystals (CNCs) with a particle length of 90 nm and width of 8 nm currently produced by acid hydrolysis of wood pulp were used in this study. The microstructures of CNCs/polymer suspensions were investigated by performing linear small amplitude oscillatory shear (SAOS) and nonlinear large amplitude oscillatory shear (LAOS), in addition to constructing CNCs phase diagrams and measuring steady-state shear viscosities. Significant viscosity increases at low shear rates coupled with high shear thinning behaviors were observed in CNCs in HEC solutions above the overlapping concentration of HEC. The physical strength of CNCs/HEC solution gels increased with the increase in CNCs concentration and resembled the weakly crosslinked gels according to the scaling of linear dynamic mechanical experiments. According to LAOS analysis, CNCs/HEC mixtures showed type III behavior with intercycle stress softening, while the samples showed stress stiffening in single cycles.Graphical abstract

Highlights

Cellulose nanocrystals (CNCs) whiskers with a particle length of 100–200 nm and a width of 6–10 nm are currently produced in pilot plants by acid hydrolysis of alkaline wood pulp with an expectation of commercialization in the near future (Ngo et al 1989, O’Connor et al 2014)
The gelation of CNCs in HEC250 and HEC720polymer solutions was macroscopically investigated by a tube inversion method
The strain amplitude of each pair of stress–strain and stress–strain rate plots are shown on the right side of the plot resulted in strong shear thinning non-Newtonian behavior by adding CNCs at very low dosages to semi-dilute hydroxyethyl cellulose (HEC) solutions

Summary

Introduction

Cellulose nanocrystals (CNCs) whiskers with a particle length of 100–200 nm and a width of 6–10 nm are currently produced in pilot plants by acid hydrolysis of alkaline wood pulp with an expectation of commercialization in the near future (Ngo et al 1989, O’Connor et al 2014). They form colloidally stable suspensions in water due to the creation of negatively charged sulfate half ester groups on surfaces (Boluk et al 1989a, Shafeiei-Sabet et al 1989, et al.).

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