Rheometry laboratory

The rheometry laboratory is equipped for the preparation of fluids and for measuring the properties of non-Newtonian fluids.

We are able to perform almost all types of rheological shear tests (viscosity, G’ and G”, normal forces, yield stress, creep, stress relaxation, etc.) in viscoplastic and viscoelastic liquids, in the range between -50 °C and 600°C, including in the nano-N.m range. In addition to the most varied geometries and other accessories, microscopy, “light scattering”, pressure cells and geometries to measure interfacial rheology are available. The laboratory is also equipped with an extensional rheometer, which allows obtaining the extensional viscosity of viscous fluids.

 

Main available equipment:

  • Rotational rheometers

Rheometers are instruments used to evaluate the rheological properties of materials through the shear stress-strain relationship in permanent, oscillatory or transient regimes. Such equipment has a variety of accessories, such as geometries (cone-plate, parallel plates and concentric cylinders) that allow the investigation of a wide range of materials and microscope.

They feature a heating and cooling control system for performing tests over a wide temperature range (-30°C to 200°C) and solvent retention systems to prevent sample evaporation. We have a controlled strain rate rheometer, namely the ARES-G2 from TA Instruments. The others are of controlled stress, in which the sample is deformed from the application of a controlled shear stress and the rheological properties of the material are calculated by analyzing the angular deflection (deformation) resulting from the stress. The models available in our laboratory are:

  • Mars III (Haake)
  • DHR-3, AR-G2, ARES-G2 (TA Instruments)
  • MCR301, MCR501 (Anton Paar)

Our rheometers are equipped with state-of-the-art accessories designed for better measurement of rheological properties, resembling real operating conditions. Some accessories are listed below.

  • Microscope for the rheometer

The DHR MMA (Modular Microscope Accessory) is an auxiliary accessory of the TA Instruments DHR-3 rheometer, whose function is to visualize the movement of the fluid concomitantly with the performance of rotational and oscillatory rheological measurements in the rheometer. The high-resolution camera allows the visualization of images in the quality of a commercial optical microscope, making it possible to use objectives of up to 100x.

For the Anton Paar MCR301 and MCR501 rheometers we have a Rheo-microscopy accessory. Furthermore, it can operate in a wide range of temperatures, from -20°C to 300°C, in which phenomena of crystallization or melting of polymers can be observed. Our rheometer can also be used together with other optical tools available, such as SALS (small-angle light scattering).

  • Counter-rotating motor for the rheometer:

The microscope for the TA rheometer has a counter-rotation tool that allows it to be rotated in the opposite direction to the upper plate, allowing the visualization point to be changed in the vertical plane due to changes in the distribution of velocities. Since the stagnation plane is fixed, the fluid can be stationary in relation to the chamber, fixing a point in the structure, which allows evaluating particles or drops (emulsion) individually. This tool is useful in investigating the droplet breaking phenomenon, for example.

  • Accessories for interfacial rheology measurements:

The DHR-3, ARES-G2 and MCRs rheometers are equipped with accessories specialized in obtaining interfacial measurements. The options are the Double Wall Ring (DWR), Du Nouy Ring and bicone interfacial system for measuring viscous and viscoelastic properties through contact with the fluid-fluid interface. In addition, we have a Langmuir Trough that can be associated with such rheometers to investigate the effect of surface pressure on interfacial rheological properties.

  • High pressure cell:

The high pressure cell is used with the Haake Mars III rotational rheometer, highly effective equipment for measuring the rheological properties of various materials. Pressure measurements can reach up to 600 bar. Pressurization can be done with hydraulic mechanisms or with the help of both inert and combustible gases. To reach the required pressures and control them, the Teledyne ISCO 260D double syringe pump is used. Through this system, it is possible to approach the real characteristics of materials subjected to pressure in industrial processes, such as paraffin deposition processes and hydrate formation in oil production lines.

  • Extensional rheometer:

The CABER (Capillary Breakup Extensional Rheometer) rheometer is used to measure the extensional properties of a material under extension. Extensional properties are obtained by monitoring the evolution of a filament given a certain stretching stress as a function of time. Viscoelastic fluids in flow processes through nozzles (coating with pressure inks), injection molding (printing) and drop formation can be evaluated using this equipment.