Rheology Testing Services performs assays to measure viscosity & viscoelastic properties​​​​​​
Deliverables
Collaboration & Responsiveness
Scientific Rigor & Experience
Flexibility with Rapid Turn-around
Detailed Report
No Bureaucratic Hurdles
Cost Effective Support for Small & Large Projects
Rheology Applications​
Research & Development
Sensory properties
Efficacy & Performance
Process optimization
Manufacturing (QbB, Quality by Design)
In-process control
Batch consistency & Stability
Delivery
Packaging
​Confirm or disprove microstructure equivalence (Q3)
OFTEN REQUESTED ASSAYS
Additional assays listed under "Assays" tab (page top)
Viscosity
Viscosity (resistance to flow) is one component of a detailed rheological profile that supports product development.
Viscosity can be quantified with several approaches, often with a shear rate ramp assay across a wide range of conditions. For example: Honey being a Newtonian material does not appreciably shear thin with increasing shear rate; whereas, mayonnaise (non-Newtonian) does.
Typically, these assays are helpful to generate shear thinning curves, often to efficiently model processes and applications. ​
Yield Stress
Yield stress is often determined by a shear stress ramp assay to quantify the rheological "breakpoint" that leads to flow.
For example: While on a flat surface, a spoonful of yogurt spreads out (flows) over a relatively short time has a much lower yield stress & yield viscosity than peanut butter, which takes much longer to spread out.
​
Yield stress determinations are helpful in the evaluation of pumpability, delivery, sedimentation potential (Stokes' Law) and feel.
Amplitude Sweep
An amplitude sweep is an oscillatory assay for which amplitude (energy input as either strain or stress) increases over time and frequency is held constant.
During this assay, the sample is increasingly deformed to determine its rheological breakpoint (LVER; Linear Viscoelastic Region) which correlates with stability. As described in the next panel, the LVER is important to determine the experimental strain or stress input for frequency-modulated assays.
​
An analogy for amplitude sweep is when molded gelatin is wiggled beyond its LVER, it falls apart.
Frequency Sweep
A frequency sweep is an oscillatory assay during which amplitude (either strain or stress) is held constant and frequency changes over time. This assay is used to measure viscoelastic properties for materials that are not amenable to rotational assays. The measurables for frequency sweep assay is stiffness (G*; complex modulus), solid nature (G'; elastic modulus), liquid nature (G"; viscous modulus), degree of fluidity (phase angle), complex viscosity, and tan delta (G"/G').
To properly perform this assay, it is important to use a strain or stress input within its LVER determined from amplitude sweep. This ensures the sample's rheological integrity is maintained during the assay and hence validity of the results.
​
Silly Putty is an excellent example of changing viscoelastic properties with frequency. When near at rest (low frequency), it slowly spreads like a liquid (G">G'). In contrast, when rolled into a ball and dropped on a table (high frequency), it bounces like a solid (G'>G"). Check out "Learn More" below to see actual plot.