Surfactants are a kind of chemical substances that has a wide
variety of applications in different industries and are very important
components of many products that we use daily.
They can be defined as substances that mainly lower the surface tension of a liquid, which is a property that the surface of liquids posses that allows it to resist to external forces. Surface tension allows some insects to run on the surface of water without sinking or a paper clip to float in water, for example. In the same way surfactants also reduce the interfacial tension between two liquids, for example water and oil. These are very important properties that have found many applications in different products like detergents, wetting agents, foaming agents, emulsifiers and dispersants.
In general surfactants are usually organic compounds which contain both hydrophobic (groups that are repelled by water, or does not like water) and hydrophilic groups (groups that are attracted and tend to dissolve in water, or does like water). The hydrophobic part is also known as the tail, whereas the hydrophilic part is known as the head of the molecule. When they are placed in water their hydrophilic groups dissolve while their hydrophobic groups tend to aggregate thus forming different structures in water such as micelles.
Surfactants act as emulsifiers. Emulsifiers are substances capable of dispersing one liquid into another immiscible liquid, for example, oil into water. When you try to mix oil and water they never mixed. Take as an example what happens when you are washing your dishes; only after you place a product containing an emulsifier (like soap) you are able to mix the oil with water thus removing any residual oily products from your dishes. This happens because the oily substance, which is hydrophobic as the tail of the surfactant, gets trapped into the micelles core and, since the micelles are soluble in water, the oily substance can be removed.
Types of surfactants
According to their chemical structure they are classified as anionic, cationic and nonionic surfactants. Anionic surfactants consist of an organic tail with a negative charged head and a small positive atom or molecule, like ammonium. These are the most common types of surfactants.
Cationic surfactants in the other hand posses an organic tail with a positive charge head and a small negative atom or molecule, like chloride. They are more expensive to produce and therefore they have limited uses.
Unlike Anionic or cationic surfactants, nonionic ones do not ionize in water because their hydrophilic part consists of non dissociable molecules like alcohols, phenol, et cetera. This ones constitute about 45% of the overall industrial production.
The last type are the amphoteric ones, which consist of a molecule that exhibit both anionic and cationic dissociation.
Some surfactants and their applications
Probably the best known surfactant is sodium dodecyl sulfate (SDS), also known as sodium lauryl sulfate (SLS). This molecule is an anionic surfactant used in many cleaning and hygienic products. Is consider a very effective substance in any task that requires the removal of oily residues. You can find it in engine degreasers, floor cleaners, car wash soaps, toothpastes, shampoos, shaving foams and bubble bath formulations.
Another common one is sodium laureth sulfate or sodium lauryl ether sulfate (SLES). SLES is inexpensive and very effective as foaming agent, a material that facilitates the formation of foam. It has been used also in many cosmetic products for their cleansing and emulsifying properties.
A substance derived from coconut oil has also been used as surfactant. Cocamidopropyil betaine is use in shampoos, soaps and many cosmetics mainly to reduce the irritation that other purely ionic surfactants can cause as this is an amphoteric molecule. It is also an antiseptic making it use suitable for a range of personal sanitary products.
They can be defined as substances that mainly lower the surface tension of a liquid, which is a property that the surface of liquids posses that allows it to resist to external forces. Surface tension allows some insects to run on the surface of water without sinking or a paper clip to float in water, for example. In the same way surfactants also reduce the interfacial tension between two liquids, for example water and oil. These are very important properties that have found many applications in different products like detergents, wetting agents, foaming agents, emulsifiers and dispersants.
In general surfactants are usually organic compounds which contain both hydrophobic (groups that are repelled by water, or does not like water) and hydrophilic groups (groups that are attracted and tend to dissolve in water, or does like water). The hydrophobic part is also known as the tail, whereas the hydrophilic part is known as the head of the molecule. When they are placed in water their hydrophilic groups dissolve while their hydrophobic groups tend to aggregate thus forming different structures in water such as micelles.
Surfactants act as emulsifiers. Emulsifiers are substances capable of dispersing one liquid into another immiscible liquid, for example, oil into water. When you try to mix oil and water they never mixed. Take as an example what happens when you are washing your dishes; only after you place a product containing an emulsifier (like soap) you are able to mix the oil with water thus removing any residual oily products from your dishes. This happens because the oily substance, which is hydrophobic as the tail of the surfactant, gets trapped into the micelles core and, since the micelles are soluble in water, the oily substance can be removed.
Types of surfactants
According to their chemical structure they are classified as anionic, cationic and nonionic surfactants. Anionic surfactants consist of an organic tail with a negative charged head and a small positive atom or molecule, like ammonium. These are the most common types of surfactants.
Cationic surfactants in the other hand posses an organic tail with a positive charge head and a small negative atom or molecule, like chloride. They are more expensive to produce and therefore they have limited uses.
Unlike Anionic or cationic surfactants, nonionic ones do not ionize in water because their hydrophilic part consists of non dissociable molecules like alcohols, phenol, et cetera. This ones constitute about 45% of the overall industrial production.
The last type are the amphoteric ones, which consist of a molecule that exhibit both anionic and cationic dissociation.
Some surfactants and their applications
Probably the best known surfactant is sodium dodecyl sulfate (SDS), also known as sodium lauryl sulfate (SLS). This molecule is an anionic surfactant used in many cleaning and hygienic products. Is consider a very effective substance in any task that requires the removal of oily residues. You can find it in engine degreasers, floor cleaners, car wash soaps, toothpastes, shampoos, shaving foams and bubble bath formulations.
Another common one is sodium laureth sulfate or sodium lauryl ether sulfate (SLES). SLES is inexpensive and very effective as foaming agent, a material that facilitates the formation of foam. It has been used also in many cosmetic products for their cleansing and emulsifying properties.
A substance derived from coconut oil has also been used as surfactant. Cocamidopropyil betaine is use in shampoos, soaps and many cosmetics mainly to reduce the irritation that other purely ionic surfactants can cause as this is an amphoteric molecule. It is also an antiseptic making it use suitable for a range of personal sanitary products.
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