Services
Rheology and Viscosity Testing
We are a rheology and viscosity testing service.
We can study rheology of liquids and soft solids using a variety of individual tests or sequences of tests, detailed below.
Rheology Test Suite
Strain Sweeps · Frequency Sweeps · Time Sweeps · Temperature Sweeps
Strain and frequency sweeps are powerful tools for characterizing fluid systems. Each oscillatory test is an important benchmark for fluid rheology testing. Our preference is to work with strain control rheometers, with separate motors and transducers. In these measurements, the frequency is fixed and the deformation or strain amplitude is progressively increased. These measurements identify fluids and soft solids as being linear or non-linear viscoelastic (VE). In the frequency sweep, the strain is fixed and the frequency range is specified as well as the number of data points per linear or log decade.
Strain sweeps can quantify yield stress behavior and cohesiveness of the dispersion. They are also a prelude to the frequency spectrum. These measurements yield storage (G’) and loss (G”) modulus components and complex viscosity function (n*)
Frequency sweeps give us a fingerprint of the state of the material we are testing.
Best for: Characterizing viscoelastic behavior and estimating yield stress with reproducible results.
Viscosity Test Suite
Step Shear Rate Measurements · Thermal Ramps · Viscosity — Newtonian, non-Newtonian, Thixotropic, Rheopexy, Dilatancy
What do these viscosity terms mean? Is your composition Newtonian or Non-Newtonian? Newtonian fluids exhibit a constant viscosity independent of deformation rate. Fluids that are non-Newtonian exhibit a viscosity function that is dependent on shear rate or shear stress. Non-Newtonian fluids may be structured or simple fluids. These non-Newtonian systems may also exhibit time dependent shear effects such as thixotropy or rheopexy. Pseudoplastic is a class of non-Newtonian fluids that exhibit decreasing viscosity with increasing shear rate. One example is a Power Law fluid.
Some fluids exhibit rheopectic behavior. In these structured systems, the viscosity increases with increasing shear rate occurring over a long or short shear rate range.
Best for: Understanding flow behavior and viscosity for formulation, process scale-up, and specification development.
Yield Stress Determinations
Strain Sweeps · Stress Relaxation
Yield stress — why is it important? It can maintain own shape and form; it relates to solid/liquid transition, infinite (very long!) relaxation time, structured systems, recovery times, and non-Newtonian behavior (typically pseudoplastic after yield). Various measurement methods can be applied, using oscillatory measurements or steady shear vane tools.
Yield sress can easily be measured from strain sweeps or from stress relaxation during step strain tests.
Best for: Structured fluids, gels, and materials where yield behavior and shape retention matter.
Our Technical Bulletins may be helpful in explaining various viscosity behaviors.
Technical Bulletin 01: Newtonian and non-Newtonian Fluids
Technical Bulletin 02: Time Dependent Shear Effects
