Rheology: viscosity and flow behaviour


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Rheology: viscosity and flow behaviour

In Alfatestlab we are experts in rheological characterization. We can support you to study the viscosity and viscoelastic properties of a wide range of fluids, semi-solid materials and dispersions: gels and hydrogels, body creams, toothpastes, oils, paints, inks, polymeric dispersions, bitumen, plastic materials, mayonnaises, jams, honey, etc.

From very low viscosity liquids up to solid materials, we can offer several types of measurements that will help understanding how and why these materials behave in some way. Discover here after!

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In Alfatestlab we provide rheology testing services to support formulation, process development and quality control processes. From very low viscosity liquids up to solid materials, we can offer several properties measurements  such as viscosity, viscoelasticity, structure and thixotropy that will help understanding how the results relate to how these materials perform:

  • Will my cream flow giving an easy spreadability feeling to the end user?
  • Will my dispersion separate in 2 phases?
  • Will my sealant be brittle and snaps under stress and deformation?
  • How this new ingredient will impact the performances of my formulations?
  • Why the mouth feel of these icecreams differ from each other?
  • Will my formulation behave just the same after production and packaging?
  • What is the difference of my product respect to this competitor?

These and many other questions can find an answer using the right rheology test.  

Most formulators, looking for some specific mechanical behavior for their products, should be aware of rheology. Good skillness and hands sensitivity are the right “tools” to get the right product, but to precisely measure these properties and ensure reproducible production a bit more of technology is needed: rheology is the right one and Alfatestlab is here to help. The following rheology tests list is what Alfatestlab can offer you:

  • Flow curve for viscous products: simple viscosity measurement (using a viscometer) can provide information on how the product will flow. Typical viscosity measurement at single flow rate is right to compare easy and stable production processes, but clear limitations must be considered anyway. The flow curve, i.e. the measurement of viscosity in a wide range of shear rates provides much better understanding of the flowability of your sample.
  • Yield stress: this analysis determines the minimum shear stress to be applied to make your material to start flowing. For some products or processes, yield stress is a must, for others this property should be limited. A stand up product must have a yield stress, while a self leveling material should not show any yield stess.
  • Creep and stress relaxation: this is probably the easiest tests to evaluate the visco-elastic properties of a material. The “semi-solid” materials, usually so called out of the rheology science, shows solid-elastic as well as liquid-viscous properties. Those two properties (expressed in numbers as Viscous and Elastic modulus) will change in function of the stress or deformation they are subject to. A complete understanding of your material behavior, in different situations, would require these analysis.
  • Oscillation: the amplitude sweep and frequency sweep are used to investigate a material assuming it is not flowing. Visco-elastic materials show very weak, as well as strong and brittle mechanical structures that can be investigated and characterized while they are at rest. Typically, the structure of a cream or gel that should stand up or show “consistency” must present a solid-elastic behavior at rest.

Last but not least, AlfatestLab offers rheology knowledge and support such as:

  • Rheological method definition: which tests to use on your sample/process simulation
  • Rheological method development: definition of the parameters to be used during each test
  • Rheological method validation
  • Rheology Advanced reporting: explanation of tests and data interpretation
  • Rheology training, from basic to custom: our experts are available to provide any type of training you may need, in your own lab or in Alfatestlab. Ask us!

The rheological properties influence many production processes (extrusion of a material, molding, spraying etc.) and the performance of finished products. Viscosity, visco-elastic properties, thixotropy etc. play key roles in the final application and often these characteristics must be different depending on product state, storage or application for instance. In AlfatestLab we are available for the characterization of your sample flow properties, both with classical rotational rheology in cone-plate configurations, flat-plate and coaxial cylinders, as well as with with other rheology techniques.

Contact us to discuss your rheological needs!