The word surfactant is a shortened form of "surface-active agent". Surfactants serve several different purposes. Primarily, we use them as a detergent, as they lather really well to remove dirt and oil. They’re also used to lower the tension between two liquids, making them much easier to mix and spread; the key property of surfactant molecules is that they are compatible with both water and oil. They’re marvellously multi-purpose! Let’s break down their uses in greater detail.
5 different functions of a surfactant:
- Detergent: Cleansing surfactants (soaps and detergents) draw the oil to the surfactant. When the surfactant is rinsed away while holding onto the oil, the oils are rinsed off with the water.
- Foaming agents: A foaming agent allows the product to remain as a foam, as opposed to collapsing back into liquid form.
- Emulsifiers: An emulsion is a mix of oils and water; emulsifiers keep the formulas from separating out into their oil and water layers, and keep the formula smooth.
- Conditioning agents: Some surfactants are useful as conditioning agents, by remaining on the hair, giving it a smooth feel due to the oily portion of the molecule.
- Solubilizers: Solubilizers are used to make oils soluble (dissolvable) into water so that the ingredients can be mixed and incorporated into water.
So there are lots of reasons that surfactants appear in our formulas. Now how do they work?
Surfactant molecules have two parts to them; a hydrophilic (water-loving) head, and a lipophilic (oil-loving) tail. When enough surfactant molecules are present in a solution they gather together to form micelles. As the micelle forms, the surfactant heads position themselves so they are exposed to water, while the tails are grouped together in the center, protected from water. The micelles work as a unit to remove soils. When they encounter dirt and oil, the micelles open up, with the lipophilic tails pulling in all of the dirt and surrounding it, while the hydrophilic heads pull the surrounded soils off the surface and into the cleaning solution. Then the micelles reform, with the tails suspending the soil in the center of the structure, protected from the water by the heads. The dirt then easily rinses off with water.
Let’s break it down even further. The reason surfactants have so many uses, is that there are actually four different types of surfactants, and each of them has different strengths and weaknesses. They are categorized by the type of charge the head carries. This part gets a little science-y, so I’m going to do my best to explain it simply!
- Anionic surfactants: carry a negative charge. These are most commonly used surfactants, as their ability to foam and lather makes them very good at cleaning, but can be irritating to skin Most of the surfactants that have “sodium” or “ammonium” in the name will be negatively charged.
- Cationic surfactants: carry a positive charge. As these don’t lather as well as anionic surfactants, they aren’t as effective at cleaning, and are more often used as a conditioning agent.
- Amphoteric surfactants: sometimes known as zwitterionic, these carry either a positive or a negative charge, depending on the pH level. At high pH, they become negatively charged, and at low pH they become positively charged. Because of this, they can perform different duties depending on the pH of the formula. They work well as detergents, and are milder than anionics, but don’t foam up as well.
- Nonionic detergents: have no electrical charge. These are the mildest surfactants, and are often used in baby products. Their lack of charge gives them antistatic properties. They are the second most common surfactant, but are often combined with others due to lack of foam.
Surfactants appear in products in many combinations and variations. Certain surfactants need to be paired with an emulsifier in order to form. Some surfactants are paired together, because one boosts properties of the other, making the mixture more effective as a whole.
One thing to note is that surfactants with sulphates often produce better lather and foam than surfactants that don’t. Because we prefer not to use sulphates, we use a blend of sulphate-free surfactants to create the shampoo and conditioner you know and love, with all the foamy goodness you could ever need!
In our products, we use two anionic surfactants, SCI (INCI Sodium Cocoyl Isethionate) and SLSA (INCI Sodium Lauryl Sulfoacetate) and one amphoteric surfactant cocoBetaine (INCI Cocamidopropyl Betaine). As a cationic surfactant, BTMS (INCI Behentrimonium Methosulfate) isn’t used as a detergent so much as a conditioning agent. It appears in every one of our shampoos, and is one of the main ingredients of our conditioners!
No cleaning product is complete without some form of a surfactant. But surfactants aren’t only used for their cleaning properties. They’re also found in things we eat, and our lungs actually produce natural surfactants! If you eat ice cream or mayonnaise, enjoy lotions or creams, wash your dishes or clothes, or condition your hair, you’re using a surfactant! There’s a whole family of surfactants with a wide range of uses.