Rheological Properties of Polymer Colloid–Cellulose Thickener Systems

Sviderskyi, Valentyn; Melnyk, Liubov; Shendera, Anna; Fleisher, Hanna

doi:10.23939/chcht12.02.207

Cited by 3 publications

(1 citation statement)

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“…1), revealed that the pure MFC suspension exhibited the lowest η 0 (≈11 kPa s), which was increasing with the addition of HEC and increasing of HEC' M W (Fig. 4) in accordance with the polymer theory (Sviderskyi et al 2018). Anyway, this was valid only for 5 w/w% and 10 w/w% of HEC addition, while, with its higher (20 w/w%) content, the η 0 was additionally increased only for the suspension containing the lowest M W HEC (HEC1 of 90.000 g/mol, to ≈27.5 kPa s), while it was decreased for samples prepared with HEC2 and HEC3, among which the suspension containing the highly M W HEC (HEC3 of 1.300.000 g/mol) resulted in the lowest η 0 (≈17.6 kPa s) among all of them.…”

Section: Rotational Tests: Flow Behavioursupporting

confidence: 81%

Influence of hydroxyethyl and carboxymethyl celluloses on the rheology, water retention and surface tension of water-suspended microfibrillated cellulose

Kokol

2022

Cellulose

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Water-soluble polymers have been shown to improve the flow rigidity and water retention ability of highly-branched (flocculated) and polydisperse water-suspended MFC, thereby also modifying and controlling their rheological behaviour. The addition of hydroxyethyl (HEC) and carboxymethyl (CMC) celluloses of different content (5–10–20 w/w%), molecular weights (MW, 90.000–1.300.000 g/mol) and degrees of substitutions (DS, 0.7–1.2) to 1.5 wt% MFC suspension, have thus been studied by evaluating their microstructure (SEM imaging), strength and rheological properties, i.e. the yield stress and flow under rotational (viscosity vs. shear rate) and oscillatory (viscoelastic) regime, using cone-plate measuring geometry at a rather low truncation gap. The pure MFC suspension showed high-viscosity at lower shear stress and shear-thinning behaviour at higher rates, with two yielding zones, indicating a secondary deflocculation of smaller and more stiffly packed fibril structures and their orientation/aligning in the direction of flow. This behaviour was reduced substantially by the addition of high-MW HEC, or almost eliminated completely by medium-MW CMCs with higher DS, yielding suspensions with higher and stability-prolonged zero-shear viscosity, as well as a more linearly decreased and irreversible viscosity profile after the shear load removal at higher shear stresses. The carboxylic groups at CMC additionally decreased the interactions between the fibrils, and subsequently reduced the fibrils’ flocks, or formed larger aggregates with their integrations, while increasing the MFC suspension gel-strength, improving its flow and viscoelastic behaviour through higher water retention ability and surface tension properties, and also its recovery after deformation.

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Section: Rotational Tests: Flow Behavioursupporting

confidence: 81%