What are emulsions
by NiuShangshen
It is a stable mixture of two immiscible liquids, one of which is uniformly dispersed in the other in the form of small droplets or particles. Emulsions are mixtures of fluids that are immiscible. Usually one fluid is present as small droplets in another phase. There are emulsions of oil in water, called oil-in-water emulsions (abbreviated as O/W), but also emulsions of water in oil (W/O). The droplet phase is called the dispersed phase, the surrounding phase the continuous phase. The interaction of its dispersed and continuous phases greatly influence the material properties of the emulsion. Emulsions can be characterized using a diverse range of analytical techniques. Some examples of common emulsions are:
Milk is an emulsion of milk fat in an aqueous solution containing many different proteins, lactose and salts. In raw milk the fat is present in the form of milk fat globules, which are surrounded by a membrane. When this milk is homogenized in the factory, these globules are broken, and the fat is dispersed into smaller droplets, also stabilized by proteins.
Margarine is an emulsion of water droplets in fat, stabilised by a packing of needle-like crystals of fat inside the continuous fat phase.
Cream is a concentrated emulsion of milk fat in an aqueous phase; the concentration depends on the type of cream.
Ice cream is a very complex product; amongst others it contains droplets of milk fat, but it also contains crystals of sugar, ice crystals and bubbles of air.
Salad dressings are made by emulsifying vegetable oil in an aqueous mixture that contains vinegar. When made at home, this emulsion is rather unstable: the droplets coalesce relatively quickly, so one has to shake it before use. Commercial variants are usually stabilized by other components.
Mayonnaise is a very concentrated emulsion of oil droplets in water, stabilised by proteins from egg yolk. The emulsion is so concentrated (70–80 vol.%) that the oil droplets are squeezed together. This squeezing together causes the nice consistency of mayonnaise.
Egg yolk is an emulsion of egg fat (and cholesterol) in an aqueous solution, stabilised by a mixture of phospholipids.
Food products. Salad dressings, gravies and other sauces, whipped dessert toppings, peanut butter, and ice cream are also examples of emulsions of various edible fats and oils. In addition to affecting the physical form of food products, emulsions impact taste because emulsified oils coat the tongue, imparting “mouth-feel.”
Waterborne paints and coatings are usually emulsions of polymer-based binder particles. They are made by making an emulsion of droplets of monomers in water, after which the monomers are polymerized to form solid particles. When applied, the water and possibly other solvents evaporate, and the binder particles fuse to form a solid layer.
Bitumen, a heavy fraction produced in the refining of petroleum, is usually too viscous to be applied directly. Therefore, bitumen is emulsified in water at high The resulting O/W emulsions have a much lower viscosity, and therefore are easier to apply. When applied (on the road or on a roof), the emulsion breaks, and the bitumen particles fuse into one layer.
Medicines & Drugs. Starch/Gelatin Blend Microparticles are prepared by the water-in-oil emulsion solvent diffusion method. The in vitro drug release content significantly depends on the starch blend ratio and the crosslinker ratio. Starch/gelatin blend microparticles should be a useful controlled release delivery carrier for water-soluble drugs. In the pharmaceutical industry, emulsions are used to make medicines more palatable, to improve effectiveness by controlling dosage of active ingredients, delayed release drugs and to provide improved aesthetics for topical drugs such as ointments.
Oils and hydrocarbons. Two third parts of the worldwide crude oils are produced in an emulsified way; these emulsions are mainly of the water-in-oil type due to the production processes.
Insecticides and pesticides. In the agricultural industry, emulsions are used as delivery vehicles for insecticides, fungicides and pesticides and are applied usually by spraying through mechanical equipment.
In cosmetics, emulsions are the delivery vehicle for many hair and skin conditioning agents. Anionic and non-ionic emulsions are used to deliver various oils and waxes which provide moisturization, smoothness and softness to hair and skin. Other examples are face creams, body lotions, shampoos, shower gels, toothpastes, soaps and fragrances.
Lubricants, slurries, additives, machine oils, polymer emulsions, glues, starch solutions, mineral filler slurries, textile emulsions, submicron emulsions and silicone emulsions.
Battery Materials. Water-based binders for batteries are developed by utilizing advanced polymer technologies, to enable the formation of negative electrodes in lithium-ion secondary batteries and nickel-hydrogen secondary batteries. Compared to conventional battery binders (PVDF), these binders have excellent binding properties, electrolyte resistance and cycle properties.
Polyelectrolyte solutions (Flocculants) for waste water treatment. Polyacrylamides are very high gramme-molecular weight polymers used as flocculants. These polymers are mainly available as a powder or an emulsion. They can be anionic or cationic. Some of these products exist in the form of highly viscous solutions (5,000 to 10,000 centipoises) that can be pumped as supplied with secondary dilution at the feeding pump delivery.
Milk is an emulsion of milk fat in an aqueous solution containing many different proteins, lactose and salts. In raw milk the fat is present in the form of milk fat globules, which are surrounded by a membrane. When this milk is homogenized in the factory, these globules are broken, and the fat is dispersed into smaller droplets, also stabilized by proteins.
Margarine is an emulsion of water droplets in fat, stabilised by a packing of needle-like crystals of fat inside the continuous fat phase.
Cream is a concentrated emulsion of milk fat in an aqueous phase; the concentration depends on the type of cream.
Ice cream is a very complex product; amongst others it contains droplets of milk fat, but it also contains crystals of sugar, ice crystals and bubbles of air.
Salad dressings are made by emulsifying vegetable oil in an aqueous mixture that contains vinegar. When made at home, this emulsion is rather unstable: the droplets coalesce relatively quickly, so one has to shake it before use. Commercial variants are usually stabilized by other components.
Mayonnaise is a very concentrated emulsion of oil droplets in water, stabilised by proteins from egg yolk. The emulsion is so concentrated (70–80 vol.%) that the oil droplets are squeezed together. This squeezing together causes the nice consistency of mayonnaise.
Egg yolk is an emulsion of egg fat (and cholesterol) in an aqueous solution, stabilised by a mixture of phospholipids.
Food products. Salad dressings, gravies and other sauces, whipped dessert toppings, peanut butter, and ice cream are also examples of emulsions of various edible fats and oils. In addition to affecting the physical form of food products, emulsions impact taste because emulsified oils coat the tongue, imparting “mouth-feel.”
Waterborne paints and coatings are usually emulsions of polymer-based binder particles. They are made by making an emulsion of droplets of monomers in water, after which the monomers are polymerized to form solid particles. When applied, the water and possibly other solvents evaporate, and the binder particles fuse to form a solid layer.
Bitumen, a heavy fraction produced in the refining of petroleum, is usually too viscous to be applied directly. Therefore, bitumen is emulsified in water at high The resulting O/W emulsions have a much lower viscosity, and therefore are easier to apply. When applied (on the road or on a roof), the emulsion breaks, and the bitumen particles fuse into one layer.
Medicines & Drugs. Starch/Gelatin Blend Microparticles are prepared by the water-in-oil emulsion solvent diffusion method. The in vitro drug release content significantly depends on the starch blend ratio and the crosslinker ratio. Starch/gelatin blend microparticles should be a useful controlled release delivery carrier for water-soluble drugs. In the pharmaceutical industry, emulsions are used to make medicines more palatable, to improve effectiveness by controlling dosage of active ingredients, delayed release drugs and to provide improved aesthetics for topical drugs such as ointments.
Oils and hydrocarbons. Two third parts of the worldwide crude oils are produced in an emulsified way; these emulsions are mainly of the water-in-oil type due to the production processes.
Insecticides and pesticides. In the agricultural industry, emulsions are used as delivery vehicles for insecticides, fungicides and pesticides and are applied usually by spraying through mechanical equipment.
In cosmetics, emulsions are the delivery vehicle for many hair and skin conditioning agents. Anionic and non-ionic emulsions are used to deliver various oils and waxes which provide moisturization, smoothness and softness to hair and skin. Other examples are face creams, body lotions, shampoos, shower gels, toothpastes, soaps and fragrances.
Lubricants, slurries, additives, machine oils, polymer emulsions, glues, starch solutions, mineral filler slurries, textile emulsions, submicron emulsions and silicone emulsions.
Battery Materials. Water-based binders for batteries are developed by utilizing advanced polymer technologies, to enable the formation of negative electrodes in lithium-ion secondary batteries and nickel-hydrogen secondary batteries. Compared to conventional battery binders (PVDF), these binders have excellent binding properties, electrolyte resistance and cycle properties.
Polyelectrolyte solutions (Flocculants) for waste water treatment. Polyacrylamides are very high gramme-molecular weight polymers used as flocculants. These polymers are mainly available as a powder or an emulsion. They can be anionic or cationic. Some of these products exist in the form of highly viscous solutions (5,000 to 10,000 centipoises) that can be pumped as supplied with secondary dilution at the feeding pump delivery.