Hydroxy Ethyl Cellulose and Exilva micro fibrillated cellulose (MFC) can both be used as rheology modifiers in a variety of industries to prevent sedimentation and settling. In this article, I review the ability of the materials to give a yield stress in a water-based system and, because of that, provide anti-settling and anti-sedimentation behavior. Tune-in on a comparison between these two rheology additives.
Hydroxy Ethyl Cellulose thickeners are made by chemically modifying cellulose with ethylene oxide. This modification transforms cellulose that is insoluble in water, into a water-soluble polymer. Dissolved Hydroxy Ethyl Cellulose polymer thickens the water phase. Also, the polymeric molecules are able to form a reversible three-dimensional (3D) network consisting of hydrogen bonds. The hydroxyl (OH) groups of HEC thickeners can form hydrogen bonds with one another and with other components that are able to form hydrogen bonds. At low shear, a water-based system containing a Hydroxy Ethyl Cellulose thickener has a high viscosity (or even a yield stress). At high shear, the hydrogen bond network breaks down and the viscosity drops.
Exilva micro fibrillated cellulose is a water-based suspension consisting of long and thin cellulose fibers, called fibrils. At low shear, the fibrils entangle with one another, thus forming a strong three-dimensional network with added interactions via hydrogen-bonding.
Both Exilva micro fibrillated cellulose and Hydroxy Ethyl Cellulose can give a yield stress in water-based systems and both additives give a shear-thinning rheology. Interested in the concept of yield stress and anti-settling? Read the details here.
Hydroxy Ethyl Cellulose and Exilva micro fibrillated cellulose: anti-sedimentation and anti-settling behavior in a TiO2 dispersion
The viscoelastic properties of paints and coatings can be improved by adding products like Hydroxy Ethyl Cellulose and Exilva micro fibrillated cellulose. By transferring the yield stress properties of Exilva MFC or HEC additives to the paint, you obtain stability against sedimentation and settling. The composition of water based titanium dioxide (TiO2) pigment dispersions (model formulations), containing a HEC thickener and Exilva MFC respectively, is given in Table 1.
The Hydroxy Ethyl Cellulose product is a commercial state-of-the-art HEC thickener that is used to adjust the rheology of water based paints. The Hydroxy Ethyl Cellulose thickener is supplied as an easy-to-dissolve powder. The micro fibrillated cellulose rheology additive, Exilva F 01-V, is supplied as a suspension of 10 % of MFC in water.
Both technologies are based on a reversible three-dimensional (3D) network that is built-up and broken down, depending on the amount of shear applied. The high efficiency of the Exilva MFC product results from the entanglements of the cellulose fibrils, giving a strong physical network, seen in Figure 1. A higher yield stress gives better anti-sedimentation and anti-settling properties. Below, i have put together an explanation of similarities and differences of the two rheology technologies