Rheology

Rheology

Rheometers for measuring the rheological properties of Non-NewtonianA non-Newtonian fluid is one that exhibits a viscosity that varies as a function of the applied shear rate or shear stress.non-Newtonian liquids and soft solids - from formulation to product use

Rheology is the study of flow and deformation of materials under applied forces which is routinely measured using a rheometer. The measurement of rheological properties is applicable to all materials from fluids such as dilute solutions of polymers and surfactants through to concentrated protein formulations, to semi-solids such as pastes and creams, to molten or solid polymers as well as asphalt.

Many commonly-used materials and formulations exhibit complex rheological properties, whose viscosity and viscoelasticity can vary depending upon the external conditions applied, such as StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress, StrainStrain describes a deformation of a material, which is loaded mechanically by an external force or stress. Rubber compounds show creep properties, if a static load is applied.strain, timescale and temperature. Internal sample variations such as protein concentration and stability, and formulation type for biopharmaceuticals, are also key factors that determine rheological properties.

Rheological properties impact at all stages of material use across multiple industries – from formulation development and stability to processing and product performance. The type of rheometer required for measuring these properties is often dependent on the relevant shear rates and timescales as well as sample size and viscosity. Examples of rheological measurements include:

• Viscosity profiling for Non-NewtonianA non-Newtonian fluid is one that exhibits a viscosity that varies as a function of the applied shear rate or shear stress.non-Newtonian shear-dependent behavior to simulate processing or in-use conditions
• Viscoelastic fingerprinting for material classification to determine extent of solid-like or liquid-like behavior
• Optimizing and assessing dispersion stability
• Determination of ThixotropyFor most liquids, shear thinning is reversible and the liquids will at some point in time gain their original viscosity when a shearing force is removed.thixotropy of paints and coatings for product application and final finish quality
• Impact of molecular architecture of polymers on viscoelasticity for processing and end-use performance
• Benchmarking food and personal care products for ability to pump or spread
• Full cure profiling for bonding or gelling systems
• Pre-formulation screening for therapeutics, particularly bio-pharmaceuticals