Cellosize

Properties keywords: non-Newtonian, shear thinning, viscous, liquid, colourless

Analogue keywords: silicate melt, bubble suspension

Common names: Hydroxyethyl cellulose (HEC), Natrosol

General Information: Cellosize is a water-soluble polymer.  It comes as a white powder, which dissolves completely and rapidly in water to produce a transparent liquid.  It is manufactured in a variety of viscosity grades, is non-toxic and easy to clean.  It is primarily used as a thickening agent in the pharmaceutical, paint, textile, food and cosmetic industries. 

Properties

Both viscosity grade and solution concentration greatly affect Cellosize viscosity (Figure 1a), however at the same conditions, viscosity is highly reproducible.  Medium to high viscosity grades (10 to 100 Pas at a strain-rate of 1 s-1 and 25°C) are highly shear thinning, that is, their viscosity decreases markedly with strain-rate (Figure 1b, Shields, 2015), but low viscosity grades (approximately 0.1 Pas at 25°C) are almost Newtonian (Dow company Hydroxyethyl Cellulose brochure).  Intermediate viscosity grades can be obtained through blending either the dry powder or liquid solutions (see the Dow company Hydroxyethyl Cellulose brochure for the calculation method).

Figure 1. a) Effect of Cellosize concentration on solution viscosity, from Dow company Hydroxyethyl Cellulose brochure and b) viscosity of Cellosize grade QP52000H against strain-rate, from Shields (2015).

Increasing temperature reduces solution viscosity however solutions can be heated up to 200°C without any decomposition.  Solutions also show no permanent loss of viscosity with shear, even when sheared to high strain-rates.  Surface tension varies between 0.065 and 0.067 N/m depending on viscosity grade.  Density of a 2 wt.% solution of high viscosity grade QP52000H is 1 x 103 kg m-3 (Shields, 2015).

Cellosize is also viscoelastic.  Viscosity shows significant time-dependence by varying from approximately 200 to 5 Pa s with increasing frequency, over the linear viscoelastic region of stress, which ranges from 1 to 10 Pa (Shields 2015).  The refractive index of Cellosize at 20°C is 1.336.

Applications

Hydroxyethyl cellulose is highly useful as a silicate melt analogue as it can replicate a wide range of viscosities.  It is also shear thinning, which more accurately replicates the behaviour of magma containing gas bubbles and solid particles (e.g. Dingwell and Webb, 1989).

Shields (2015) characterized the rheology of Cellosize and found that it conforms to a Cross model rheology and approximates a bubble suspension with 42 vol.% exsolved bubbles.  This makes Cellosize useful for experiments of bubbly liquids where imaging is required, because the visual difficulties associated with using an actual suspension of bubbles are avoided.

It has been used as a magma analogue in studies of the propagation of liquid filled cracks acting as precursors for large volcanic eruptions (de Bremond d’Ars et al., 2001), and in studies of the transport and settling of magmatic sulphides in mafic magma (Menand and Tait, 2001).

Zhang et al. (1997) and Zhang (1998) used hydroxyethyl cellulose to increase the viscosity of water to 5 Pas in their experiments simulating gas-driven eruptions and to observe the effect of viscosity on eruption dynamics.  Furthermore they found that the polymer is useful for multi-component experiments because it does not affect the solubility or diffusivity of carbon dioxide in water.

Limitations and tips for use

Solutions of hydroxyethyl cellulose should be prepared by adding cold water to the required amount of powder and applying continuous agitation for approximately 30 minutes at room temperature, when it will turn clear.  The liquid should then be left to stand to allow entrained air bubbles to rise out of solution. WP types should be sprinkled into vigorously stirred water instead.

Note: for many grades the mixture will become lumpy at concentrations over 2 wt.%.  Furthermore, if preparing high viscosity solutions, be aware that mixtures will flow at very low speeds and bubbles/particles will rise/settle very slowly.

The viscosity achieved can be affected by humidity of the powder, therefore containers should have a tight seal.  Hydroxyethyl cellulose is non-toxic, however inhalation of dust may cause irritation to the upper respiratory tract.

References

de Bremond d’Ars J, Arndt NT, Hallot E (2001) Analog experimental insights into the formation of magmatic sulfide deposits. Earth and Planetary Science Letters 186: 3–4, 371– 381

Dingwell DB, and Webb SL (1989) Structural relaxation in silicate melts and non-Newtonian melt rheology in geological processes. Physics and Chemistry of Minerals 16: 508–516

Dow Company Hydroxyethyl Cellulose Brochure (2015) http://www.dow.com/assets/attachments/industry/building_construction/Cellosize_brochure.pdf

Menand T and Tait SR (2001) A phenomenological model for precursor volcanic eruptions. Nature 411: 678-680

Shields J (2015) Shear deformation of highly viscous magmas: a textural study of strain localisation. PhD thesis, University of Bristol, UK.

Zhang Y, Sturtevant B, and Stolper E (1997) Dynamics of gas-driven eruptions: experimental simulations using CO2-H2O polymer system. Journal of Geophysical Research 102: B2, 3077-3096

Zhang Y (1998) Experimental simulations of gas-driven eruptions: kinetics of bubble growth and effect of geometry. Bulletin of Volcanology