Rheology and Rheological Measurements

Abstract

This article presents the experimental measurement of the rheological properties of both liquids and solids and the principles on which these measurements are based. The flow properties of a liquid are defined by its resistance to flow, that is, viscosity. This concept is defined and discussed in terms of both theoretical flow models and practical consequences. Temperature, thixotropic and other time‐dependent, and concentration effects are covered for dilute polymer solutions, melts, and dispersed systems. Techniques and viscometers for capillary, rotational, and moving‐body measurements are described. The rheological properties of viscoelastic solids are made up of a combination of permanent deformation and recoverable elastic deformation. Additionally, a number of liquids show elastic and flow behaviors, which are commonly termed as the viscoelastic materials. Some additional techniques have been included beyond those indicated for simple solids and liquids, which are needed for a complete characterization of the mechanical behavior of materials in terms of elasticity and viscoelasticity. Examples of such methods are the dynamic measurement of response to sinusoidal oscillatory motion; the measurement of flow with time after application of stress, that is, creep; and the measurement of the rate and degree of recovery after removal of stress, that is, creep recovery or recoil. A few special topics, including the Weissenberg effect, time–temperature superposition principles (TTSP), and electrorheological measurements, are also discussed. Nonlinear dynamic measurements of the complex fluids in terms of the large amplitude oscillatory shear (LAOS) measurements, including the Fourier transform rheology and Lissajous curves, are discussed.

Rheological properties of high‐pressure treated xanthan gum and guar gum blend solutions: A response surface approach

“…Similar increasing patterns of the G 0 for individual hydrocolloid solutions with concentration have been observed (Ahmed, 2021a(Ahmed, , 2021b(Ahmed, , 2022Ahmed & Ramaswamy, 2004).…”

“…Following our previous work (Ahmed, 2021a(Ahmed, , 2021b(Ahmed, , 2022, sealed pouches containing blended gums were merged into a water medium in a 2 L high-pressure vessel, and the high-pressure treatment was performed (Avure Technologies, WA, USA) at 26 C. The pressure intensities varied from 300 to 600 MPa, with a constant holding time of 15 min. For pressurization, water was used.…”

“…The time-pressure and time-temperature curves were superimposed at a reference pressure and temperature of 300 MPa and 40 C, respectively. More details for the construction of the TTS master curve can be obtained elsewhere (Ahmed, 2021a(Ahmed, , 2021b(Ahmed, , 2023.…”

Three‐dimensional printing and its application to legume proteins: A review

“…Shear stress–shear rate rheograms illustrating various types of flow behaviors (Reference: Ahmed, 2021)…”

“…In small‐amplitude oscillatory measurements, the viscoelasticity of the inks can be described in terms of the elastic modulus ( G ′), viscous modulus ( G ″), phase angle ( δ ), or complex viscosity ( η *). Readers can consult elsewhere for more details about basics of rheology (Ahmed, 2021).…”