Emulsions are dispersions of two immiscible liquids. They are of interest in many important practical applications in the food, cosmetic, oil production, agriculture, chemical, oil & gas, pharmaceuticals and several other process industries.

There are two types of emulsions: Oil-in-water (O/W) type, where oil forms the dispersed (droplets) phase and water forms the continuous phase; and water-in-oil (W/O) type, where water forms the dispersed (droplets) phase and oil forms the continuous phase. Without an effective interfacial stabilizer, emulsions are unstable systems and they readily separate out into oil and water phases as the mechanical agitation is stopped.

One of the most important of emulsions is their inherent instability. Though the dispersed drops are small, gravity exerts a measurable force on them and overtime they coalesce to form larger drops which tend to either settle to the bottom or rise to the top of the mixture. This process ultimately causes the internal and external phases to separate into the two original components. Depending on how the emulsion is formulated and the physical environment to which it is exposed, this separation may take minutes, months, or millennia.

• An emulsion is a type of colloid formed by combining two liquids that normally don’t mix.
• In an emulsion, one liquid contains a dispersion of the other liquid.
• The process of mixing liquids to form an emulsion is called emulsification.
• Even though the liquids that form them may be clear, emulsions appear cloudy or colored because light is scattered by the suspended particles in the mixture.
• Safety and environmental friendliness ensured by using water as a solvent
• Viscosity can be easily adjusted
• Suitability for gluing and coating applications derived from emulsion’s property of forming a film when dried
• Excellent miscibility with pigments, solvents, additives, etc

An emulsion is prepared by shaking strongly the mixture of the two liquids or by passing the mixture through a colloid mill known as the homogenizer. The emulsions thus prepared from the pure liquids are usually not stable and the two liquids separate out on standing. To get a stable emulsion, small quantities of certain other substances are added during preparation. The substances thus added to stabilize the emulsions are called emulsifiers or emulsifying agents. The substances commonly used as emulsifying agents are soaps of various kinds, long chain sulphonic acids or lyophilic colloids like proteins, gum, and agar.

Emulsions may be prepared by several methods, depending upon the nature of the components and the equipment. On a small scale, as in the laboratory or pharmacy, emulsions may be prepared using a dry Wedgwood or porcelain mortar and pestle or a mechanical blender or mixer. On a large scale, large mixing tanks may be used to form the emulsion through the action of a high-speed impeller.

• The viscosity of emulsions varies depending on the temperature.
• As the temperature decreases, the viscosity increases.
• By adding water, the viscosity can be adjusted to a lower viscosity
• To increase the viscosity, emulsion thickeners may be used

Viscosity measurement is an extremely useful technique for quality control.

• During homogenization, many emulsions will undergo a substantial viscosity increase as the droplet size is reduced. The amount of this increase will, therefore, be a good indicator of emulsion quality.
• Concentration of the emulsion bears strong correlation with the emulsion viscosity, hence the viscosity information can be effectively used to predict concentrations with pre-defined or user-defined models.
• During the mixing process, characterizing the viscosity – inline can be useful in determining the emulsion stability, desired end point of the mixing/blending system and to ensure continuity. If need arises, adjustments to stirring intensity, rotational speed, equipment may be made depending on the measured viscosity data and its interpretations.
• Emulsions are complex systems with a wide range of applications and commercial uses. Accurate characterization of emulsions with the viscosity data is critical to ensure emulsion stability and performance.

Viscosity measurement obtained with an inline viscometer can provide an excellent QC benchmark and ensure QA/QC of the process and end-product. Please read our application note.

Rheonics density meters and viscosity meters are available as probes and flow-through systems for installation in blending skids, storage tanks, loading terminal, process lines and in transport vessels. All Rheonics products are designed to withstand harshest process environments, high temperature, high level of shock, vibrations, abrasives & chemicals.

High stability and insensitive to mounting conditions: Any configuration possible

Rheonics SRV and SRD use unique patented co-axial resonator, in which two ends of the sensors twist in opposite directions, cancelling out reaction torques on their mounting and hence making them completely insensitive to mounting conditions and flow rates. Sensor element sits directly in the fluid, with no special housing or protective cage requirements.

Instant accurate readouts on production quality – Complete system overview and predictive control

Rheonics’ RheoPulse software is powerful, intuitive and convenient to use. Real-time process fluid can be monitored on the integrated IPC or an external computer. Multiple sensors spread across the plant are managed from a single dashboard. No effect of pressure pulsation from pumping on sensor operation or measurement accuracy. No effect of vibration.

Inline measurements, no bypass line is needed

Directly install the sensor in your process stream to do real time viscosity (and density) measurements. No bypass line is required: the sensor can be immersed in-line; flow rate and vibrations do not affect the measurement stability and accuracy.