Rheology & Interfacial Properties of Fluids

Viscoelastic materials display a behaviour that lies between that of liquids and solids. While viscosity measures the resistance to flow, elasticity measures the flexibility due to microstructures that exist within fluids. In nature, materials such as polymers, emulsions and slurries may display both viscosity and elastic properties. Common examples of viscoelastic materials are mayonnaise, ketchup and produced oil-water mixtures produced from oilsands which are significantly different from pure oil and water phases.

Rheology can tell us how easy or difficult is it to flow an oil through a pipeline, or how difficult will it be to separate oil and water phases from emulsions produced from SAGD operations or oilsands processing, information we routinely utilize to improve processes or to develop new ones. Rheology is also an important tool in development of new liquid coatings for machines, equipments and pipelines, and in new foods and beverage development.

By studying interfacial properties of fluids, we develop processes to separate oil and water, or understand why emulsions form in first place. Interfacial properties that can be measured in house are surface tension, interfacial tension, surface charge, drop/particle sizes and size distributions, electrical conductivity, coalescence and flocculation kinetics, interfacial viscosity, surface wettability, contact angles on fibres/powders, and planar surfaces.

We also have the capability to examine/visualize emulsions through high-definition microscopes and determine drop sizes and drop size distributions. For solid materials we have SEM facility which allows for material topography and surface structures to be studied using an electron beam.

To conduct our rheology work we have several pieces of equipment and methods available in our laboratory that we routinely utilize to study emulsions and other liquids and semi-solid soft matter. The equipments and methods are listed below: 

• Equipment to Produce Emulsions: Ultrasonic horns and probes (various sizes), mixers, propellers and impellers (various sizes, geometric types, functionalities and energy efficiencies). Temperature controlled mixing facility.  
• Rheometer: Viscosity and elasticity of liquids and emulsions. Various shearing and temperature capabilities.   
• Microscopes: Light high-definition microscope and electron type (SEM) to study and quantify drops or emulsions or visualize solid surfaces and microstructures at microscale.  
• Acoustic Particle Sizer: Uses a soundwave signature to measure the size of particles and emulsion drops. Utilized especially for dark bitumen that light cannot penetrate. 
• Beckman Coulter Particle Sizer: Measures particles size in slurry. 
• Surface and Interfacial Force Tensiometer: Measures the force that exists between a pure liquid phase and air, or between two immiscible phases (like oil and water).  
• Zeta Potential Meter: Measures the strength of the electrical charge on the oil drops (like oil-water emulsions). 
• Electrical Conductivity Meters: Measure electrical conductivities of oil and water phases. Different probes available for liquid types.  
• Turbiscan and Lumisizer Analyzers: Computer controlled tracking of how fast emulsion drops move and settle out over hours, days, and weeks under different temperatures and environmental conditions (normal-gravity or enhanced gravity conditions). 
• Contact Angle Analyzer: Detects the affinity (wettability) between oil or water drops (or an emulsion) and a surface (all sort of metals, silica, powders etc.). Used to formulate and develop coatings or processes to ensure oil or emulsions will not stick too heavily to surfaces in contact and prevent mechanical issues on equipment and contact surfaces. 
• Turbidity Meter: Laser scanning to determine how turbid or clean an emulsion or a slurry is.  
• Total Organic Carbon Analyzer: Determines the concentration of oil, impurities present in aqueous samples. 
• Karl Fischer: Determines water content in an oil phase.  
• Centrifuges: For separation of oil-water phases. Temperature controlled and various sample sizes can be processed.