Gelation of crystalline nanocellulose in the presence of hydroxyethyl cellulose

Abstract

In this work, hydroxyethyl cellulose (HEC) was used to induce gelation of electrosterically stabilized cellulose nanocrystal (ECNC) and common cellulose nanocrystal (CNC) suspensions. The main goals were to shift the gelation point to low concentrations of nanoparticles and clarify the role of interactions between ECNCs in contrast to CNCs. The rheological properties of CNC suspensions were investigated in the presence of HEC with or without CaCl2 while ECNC suspensions would be only mixed with HEC since the addition of salt would not alter the viscoelastic properties of the whole system. The structure build‐up kinetics as well as the viscoelastic properties of the suspensions were compared. CaCl2 was used to induce gelation of CNC suspensions at a solid content as low as 0.2 g/g in the presence of HEC. ECNC suspensions were less sensitive to HEC since the best result obtained for inducing gelation was achieved at a concentration of 4 g/g. All the results presented are explained by the adsorption of HEC on the nanoparticles, which was determined by viscometry. High adsorption level of HEC chains imparted CNCs better colloidal stability in the presence of CaCl2 as compared to pristine CNCs, whereas it did not affect the ECNC colloidal stability.

Tailoring cellulose nanocrystals rheological behavior in aqueous suspensions through surface functionalization with polyethyleneimine

“…Both the freeze-drying and calcium chloride methods of PEI determination in supernatant gave similar results with the maximum possible adsorption of PEI being around 200 mg per g of CNC. Similar to the adsorption of hydroxyethyl cellulose onto the CNCs (Lenfant et al, 2017), the adsorption of PEI was also seen to follow the Langmuir model that can be expressed as…”

“…To quantify the adsorption of PEI onto the CNC particles, an isothermal adsorption study involving viscometric analysis similar to a previously reported work (Lenfant et al, 2017) was performed on a CANON-Fenske Ubbelhode viscometer with a capillary diameter of 50 µm. A calibration curve of the relative PEI viscosity and concentration was plotted and fitted with the Kraemer-Huggins equation for intrinsic viscosity.…”

“…This method relies on the assumption that the electrostatic interaction between CNC and PEI would remain unaffected in the presence of salt. While the use of calcium chloride salt has been studied before for the adsorption of hydroxyethyl cellulose onto CNCs (Lenfant et al, 2017), it is difficult to confidently extrapolate it to the adsorption of PEI onto CNCs without strong experimental proof. Thus, a second methodology was also studied, which is based on the fact that the CNC-PEI particles do not re-disperse in water after they have been dried (see the section titled Re-dispersion of freeze-dried particles in water).…”

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

“…For nonionic polymers such as PVA or PEG, negligible enhancement in the viscosity was observed, and this may be attributed to their more flexible chains. In another study, Lenfant et al used hydroxyethyl cellulose to induce gelation of CNCs suspensions (Lenfant et al 1989). This study explained that gelation is by the adsorption of HEC on CNCs and bridging.…”

Preface of the 66th Canadian Chemical Engineering Conference: “Sustainability and Prosperity”

“…This special issue section would have not materialized without the efforts of the contributing authors and the reviewers to ensure, despite their busy schedules, that all accepted papers meet the quality standards of The Canadian Journal of Chemical Engineering . The guest editors are also sincerely thankful to the Editor‐in‐Chief of The Canadian Journal of Chemical Engineering , Prof. João Soares, for his support and guidance, and to his editorial staff for their efforts, in welcoming this series of papers on timely topics.…”