Exploring the gelation of aqueous cellulose nanocrystals (CNCs)-hydroxyethyl cellulose (HEC) mixtures
Jonathan Stolz, Hale Oğuzlu, Zahra Khalili, Yaman Boluk
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.