Rheological properties

Viscosity and viscoelasticity – from formulation to product use.

Rheology is the study of flow and deformation of materials under applied forces. 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. Rheological properties can be measured from bulk sample deformation using a mechanical rheometer, or on a micro-scale using an optical technique such as Microrheology.

Many commonly-used materials and formulations exhibit complex rheological properties, whose viscosity and viscoelasticity can vary depending upon the external conditions applied, such as stress, strain, timescale and temperature. Internal sample variations can also be key factors, such as protein API concentration and excipient type for biopharmaceuticals.

Rheological properties impact at all stages of material use across multiple industries – from formulation development and stability to processing to product performance. Examples of rheological measurements include:

Viscosity profiling for non-Newtonian shear-dependent behavior to simulate processing or use conditions.
Viscoelastic fingerprinting for material classification to determine extent of solid-like or liquid-like behavior.
Optimizing dispersion stability.
Determination of 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.
Early formulation screening for biopharmaceuticals.