For products such as coatings, foods, pharmaceuticals, cosmetics and building materials a knowledge of rheological properties offers an instant insight into otherwise hidden attributes that contribute to their processing, handling, stability, texture and performance.
Our customers use our rheology testing lab services to:
- Predict suspension or emulsion stability
- Reformulate with alternative ingredients
- Benchmark against their competitors and reverse engineer to a target or reference formulation
- Understand the impact of processing and filling on the final product
- Predict sensory and texture properties to reduce dependence on sensory panels
On receipt of your samples we will:
- Identify the properties (e.g. viscosity, viscoelasticity, thixotropy and yield) of most relevance to your needs
- Perform expert measurements using validated test methods on world-leading rheometers.
- Present our results to you and provide you with all the Q&A support you need to fully exploit our analyses.
Get a rapid rheology profile of your products or those of your competitors
Rheology measurement methods
Start with a Rheology Snapshot….
For a super-quick insight into overall rheology properties a rheology snapshot is typically the best starting point and very often delivers the required actionable insights for our clients to move ahead with their formulation or process choices. The rheology snapshot consists of a structure and flow profile and covers:
- Viscosity measurements performed across a range of shear rates. Viscosity results are typically reported in units of Pascal seconds (Pa.s) or centiPoise (cP)
- Oscillatory stress or strain sweeps to obtain storage modulus (G’), loss modulus (G”) yield stress (strength) and phase angle.
The results are easy to understand and interpret.
…then choose a deeper rheological analysis…
Various options exist to then reveal further insights into your materials.
Thixotropic materials are those that show a time-dependent viscosity change following either the application or the cessation of shearing. Thixotropic liquids typically include suspensions and emulsions, where the breakdown and subsequent recovery of colloidal structures is not instantaneous but takes time to progress to a new equilibrium state. The most commonly required output of a thixotropy measurement is a quantification of “thixotropic recovery rate”, the time taken for viscosity to rebuild to an acceptable level after shear is removed. This determines, for example, the ability for a coating or ink to maintain position following application or the ability for an adhesive to “grab” and maintain contact whilst a cure proceeds. “Thixotropic breakdown rate” is also of interest in situations such as pump or process start-up, where assembled structured is to be disruopted to initiate flow, and the application of products to the skin, where a protracted thixotropic breakdown can result in poor spreadability.
Viscoelasticity analyses can predict behaviours that lead to handling and appearance properties, lubricity, stringing and tailing, film-formation and potential pumping issues. Small angle oscillatory shearing, also known as dynamic rheological profiling delivers storage (or elastic) modulus (G’) and loss (or viscous) modulus G”, phase angle and/or tan delta measurements. Normal stress measured under shearing can predict the extensional rheologies that lead to long, stretchy textures and processing and filling problems.
This special case of viscosity predicts the mobility of suspended particles or emulsified droplets when a material is in an almost at-rest condition. The measurement takes place at incredibly low rotational rates (as low as one revolution in three months!) but only takes half an hour or so to perform. Zero-shear viscosity measurements are repoorted in Pascal seconds (Pa.s) or Poise (P)
Temperature profiling and cycling
For materials that undergo phase changes such as melts and crystallisations, oscillatory temperature sweeps can provide excellent thermorheological fingerprints that are excellent for benchmarking and second sourcing waxes and hydrocarbon-based products. For starch slurries that gelatinize or thermoset adhesives and resins that undergo gelation and curing oscillatory temperature sweeps or isothermal time sweeps enable the easy identification of key points such as viscosity minima, cure times and gel points. Furthermore the influence of storage temperature cycles can be investigated with cyclic oscillatory “swing” tests.
Creep and recovery
Creep testing delivers strain or compliance measurements as a function of time under very low stresses. Creep testing is often employed as a means for obtaining zero-shear viscosity but can also provide rapid indications of the propensity for materials to sag or slump following deposition and application.