Properties of Carbopol Solutions as Models for Yield-Stress Fluids

• Published in: Journal of food science Vol. 67; no. 1; pp. 176 - 180
• Main Authors: Curran, S.J., Hayes, R.E., Afacan, A., Williams, M.C., Tanguy, P.A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.2002; Institute of Food Technologists; Wiley Subscription Services, Inc
• Subjects: Biological and medical sciences; Carbopol solutions; Fluids; Food engineering; Food industries; Food products; Food science; Fundamental and applied biological sciences. Psychology; General aspects; pH dependence; Polymers; viscosity; yield-stress fluids; Non Newtonian fluid; Viscosity; Thickening agent; pH; Polymer; Models; Food additive; Rheological properties
• ISSN: 0022-1147; 1750-3841
• DOI: 10.1111/j.1365-2621.2002.tb11379.x

The effect of pH on the non‐Newtonian viscosity (η)of aqueous Carbopol 940 solutions is presented with high resolution (pH increments about 0.4) between pH = 2.8 and 12.7. Aqueous NaOH was used to adjust pH of 1.48 wt % Carbopol solutions. A Contraves viscometer was used to measure steady‐flow shear stress at known shear rate (γ) over the range γ= 8 to 195 s−1. Yield stresses and shear‐thinning η(γ) were observed. Data were fitted with a Herschel‐Bulkley model, whose parameters (including yield stress) were expressed as functions of pH. Comparisons were made of η(γ) to the dynamic viscometric properties η′(ω) and η*(ω) for comparable ranges of γ and frequency (ω): A fairly close match was found between η and η* but η«η′. pH dependence included previously unreported extrema of h(pH) in the range of pH = 6.2 to 6.6. Because of sensitive control of rheological properties with pH, Carbopol solutions can be used to mimic a great range of shear‐thinning and yield‐stress behavior that should make them useful for model studies directed toward process and equipment design and evaluation.