Abstract
The linear dynamic viscoelastic properties and non-linear transient rheology of sodium carboxymethylcellulose solutions (Na-CMC) in propylene glycol/water mixtures were investigated. Measurements were carried out for the solutions of Na-CMC with three different degrees of substitution (DS), namely 0.62, 0.79, 1.04, and the similar average molecular weight (Mw ≈ 250,000 g/mol). The strong synergism between the molecules of Na-CMC with DS of 0.62 and 0.79, and propylene glycol has been observed. The occurrence of the overshoot shear stress and the low loss tangent values indicate the physical cross-linking of the polymer chains. The increase of propylene glycol concentration over 80 wt% and sodium carboxymethylcellulose (DS = 0.7) over 1.6 wt% leads to the formation of a physical cross-link network. The absence of overshoot shear stress and terminal behaviour in SAOS flow of the Na-CMC1.04 solutions in the PG/water mixture shows that no intermolecular cross-linking of polymer chains occurred in them.
Highlights
The sodium salt of carboxymethylcellulose (NaCMC) is a water-soluble derivative of cellulose which has found applications in a number of industrial sectors including food, paints, pharmaceuticals and cosmetics (Li et al 2009; Kono et al 2016)
The intensity of the spectra recorded for different solutions depends on the non-linear transient rheology of sodium carboxymethylcellulose solutions (Na-CMC) degrees of substitution (DS) level; it was assumed that hydrogen associates had been formed between OH groups coming from Propylene glycol (PG) and OH groups along the cellulose chain
The study presents results obtained in measurements of small amplitude oscillatory shear flow and transient shear flow performed for sodium carboxymethylcellulose with varying degrees of substitution in a PG/ water mixture
Summary
The sodium salt of carboxymethylcellulose (NaCMC) is a water-soluble derivative of cellulose which has found applications in a number of industrial sectors including food, paints, pharmaceuticals and cosmetics (Li et al 2009; Kono et al 2016). It serves as a viscosity modifier, thickener, emulsion stabilizer, and water-retention agent (Li et al 2009). There have been relatively few reports on the physical cross-linking gel of Na-CMC. The studies investigated the conformation of Na-CMC macromolecules in diluted solutions
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