Surfactants are highly versatile products in the chemical industry, used across various sectors from household detergents to drilling muds, and from food products to pharmaceuticals. The term "surfactant" is derived from "surface active agent." These molecules are amphiphilic, meaning they have both hydrophobic and hydrophilic parts, and they naturally align at the air-water interface. In this alignment, the hydrophobic part extends into the air while the hydrophilic part remains in the water, leading to a reduction in surface or interfacial tension.

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Surfactants are classified based on their head group

Surfactants are amphiphilic molecules with distinct hydrophobic and hydrophilic components. The hydrophobic tail can be a hydrocarbon, fluorocarbon, or siloxane. Surfactants are generally categorized based on their polar head groups, as the hydrophobic tails are usually similar.

Anionic surfactants are surfactants with a negatively charged head group, making them highly effective at removing dirt and grease. They are widely used in household cleaning products such as laundry detergents, dishwashing liquids, and shampoos due to their excellent foaming and cleaning properties. Anionic surfactants are also utilized in industrial applications, including textile processing and emulsification in agriculture. Common examples of anionic surfactants include Sodium Lauryl Sulfate (SLS) and Sodium Laureth Sulfate (SLES), both known for their ability to create rich lathers and effectively break down oils and fats.

Cationic surfactants possess a positively charged head group, which gives them unique properties such as antimicrobial activity and the ability to bind to negatively charged surfaces. These surfactants are commonly used in fabric softeners, hair conditioners, and antistatic agents due to their conditioning effects and ability to reduce static cling. In addition, cationic surfactants are utilized in disinfectants and sanitizers because of their effectiveness in killing bacteria and viruses. Examples of cationic surfactants include benzalkonium chloride and cetyltrimethylammonium bromide, both of which are frequently used in personal care and cleaning products.

Non-ionic surfactants are characterized by their lack of electrical charge in the head group, which makes them particularly useful in applications where compatibility with various substances is important. They are commonly used in stabilizing emulsions, such as oil-in-water and water-in-oil emulsions, and are prevalent in cosmetic products designed for sensitive skin, baby care, and everyday skin care. Additionally, non-ionic surfactants are used in household cleaning products like laundry detergents, toilet bowl cleaners, and dishwashing detergents due to their resistance to water hardness. Examples of non-ionic surfactants include Tween 20 and Triton X-100.

Zwitterionic surfactants contain both positive and negative charges within the same molecule, allowing them to exhibit unique properties such as high solubility and low irritation potential. These surfactants are particularly useful in personal care products like shampoos and body washes, where mildness and compatibility with the skin are important. They are also employed in the formulation of pharmaceuticals and cosmetics due to their ability to stabilize proteins and emulsions. Examples of zwitterionic surfactants include cocamidopropyl betaine and sulfobetaine, both of which are valued for their gentle cleansing and foaming capabilities.

Surfactants absorb at interfaces

Due to their amphiphilic nature, surfactants are absorbed in the air-water or oil-water interface. At these interfaces, surfactants align such that the hydrophobic part is in the air (or oil) and the hydrophilic part is in the water.

Focusing on the air-water interface, the strong cohesive forces between water molecules result in high surface tension. When surfactants are absorbed, they disrupt these interactions. The intermolecular forces between surfactant and water molecules are weaker than those between water molecules, leading to a reduction in surface tension. At high surfactant concentrations, micelles form, with the concentration at which this occurs known as the critical micelle concentration.

The primary function of surfactants is to reduce surface and interfacial tension and stabilize interfaces. Without surfactants, tasks like washing laundry would be challenging, and products like mayonnaise and ice cream might not exist. Therefore, optimizing surfactants for various applications is crucial, with surface and interfacial tension measurements playing a key role in this process.

If you would like to read more about how surfactants are utilized in the industry, please download the overview below.

If you look at a cleaning product label from a company who refuse to disclose their ingredients (the bad guys), you’ll often see something like this.

Aside from not actually telling you anything of note, the labels will always refer to Anionic and Nonionic Surfactants.

Even for me, this means very little.

What the heck are Anionic or Nonionic surfactants?

The purpose of this article is to demystify all of that, and explain exactly what these labels are referring to.

What are surfactants?

It can be difficult to remove greasy stains with water, so manufacturers add surfactants to cleaning products.

Surfactants are essentially cleaning agents.  Soap is an example, although these days manufacturers tend to use synthetic detergents.

They are actually very smart chemicals that have two opposing ends.  One end of the chemical is soluble in water and the other in fat.  Hence, a surfactant can help mix oils and waters (which would normally sit on top of one another).  When you have a liquid sitting on top of oil, there’s a lot of surface tension.  Surfactants, by mixing the two, can reduce this surface tension, helping to wash away oily and water-based stains.

The chemistry of surfactants is complex, and most cleaning products use a blend of carefully chosen surfactants (e.g. fabric softeners require different surfactants to handwashes). Surfactants are categorized by the ‘chemical charge’ of their water-soluble end:

1. Ionic (surfactants that have a charge)

An ionic surfactant is one that has an electric charge.

There are three types of ionic surfactant:

• Anionic (negatively charged)
• Cationic (positive charge)
• Amphoteric (contains a positive and negative charge)

Anionic surfactants are commonly found in laundry detergents, handwashes, kitchen cleaners, body washes.  They are the most widely used and versatile surfactants.  They are the most effective at removing oily residue.  But, as the most potent surfactants, also cause skin irritation.

Contact us to discuss your requirements of Anionic Surfactant. Our experienced sales team can help you identify the options that best suit your needs.

Additional reading:
Calcium Carbide Powder - Nanorh

The most popular and widely used surfactants, anionic surfactants can be found in almost every cleaning product. It’s estimated that 45% of the $46 billion global surfactant market is made from anionic alone [1]. The most popular anionic surfactants are [2]:

• Sodium lauryl sulfate (SLS)
• Sodium laureth sulfate (SLES)
• Ammonium lauryl sulfate (ALS)
• Ammonium laureth sulfate (ALES)
• Sodium stearate
• Potassium cocoate

Anionic surfactants can be produced from a range of raw fats and oils, including soybean, palm, tallow, and coconut. This has led to the development of milder anionic surfactants such as ‘potassium cocoate’, which reduces skin irritation and palm oil consumption while improving ecological sustainability (although are more expensive) [3].

The other two ionic surfactants are used much less frequently.

Cationic surfactants are commonly found in fabric softeners and disinfectants.  They are less commonly found in household products, but cationic surfactants are more effective at killing microorganisms, and so are used as disinfectants.

Amphoteric surfactants are most commonly found in shampoos and body washes.  These are the least potent surfactants and are found in personal care products designed for sensitive skin.  They are also good foaming agents, so are also used in handwashes.

2. Nonionic (no charge)

Nonionic surfactants contain no charge.  They are commonly found in laundry and dishwasher detergents.  They are the second most widely used surfactants after anionic.  These molecules have no charge and so they are less likely to form a ‘soap scum’ in hard water. They are generally less effective than anionic, but for some people cause less skin irritation.

If anionic are the most popular surfactants, nonionic are a close second, widely used in a range of cleaning, personal care, and disinfectant products as well as industrial processes. The most common anionic surfactants are:

• Cocamide monoethanolamine (Cocamide MEA)
• Cocamide diethanolamine (Cocamide DEA)
• Fatty alcohol ethoxylates
• Amine oxides
• Sulfoxides

In areas with hard water (high mineral content), nonionic surfactants are more heavily marketed, as they are less likely to form a soap scum [4]. The nonionic surfactants are less likely to cause skin irritation, but this is associated with a less potent cleaning ability.

Most cleaning products blend anionic and nonionic surfactants to balance cleaning potential with the risk of skin irritation.

How can I tell if an ingredient is anionic or nonionic?

In most countries, there is no legal requirement for cleaning products to specify which surfactants they use (including the US and EU).  It’s a bad situation, that led to the formation of this site.  We will only review products that have full ingredient disclosure.  Otherwise, it’s impossible to know what kind of surfactant is giving you an itch, a rash or much worse.

Here’s what I mean.  The following are examples of common cleaning product labels – showing the extent of the available information in mainstream laundry detergents.

Tide Original Scent HE Turbo Clean Liquid Laundry Detergent (US)

• ‘Biodegradable surfactants (anionic and nonionic)’

Persil Non-Bio Laundry Liquid (UK)

• ‘15-30% Anionic surfactants. 5-15% Nonionic surfactants. Soap <5%’

Ecover Ökologisches Woll- und Feinwaschmittel (Germany)

• ‘5-15% Anionic surfactants, <5% Nonionic surfactants, Soap’

With the provided information it’s easy to tell the blend and type of ingredients, but impossible to determine the specific chemicals.

That said, even if the ingredients were all listed, there is no straightforward way to identify between an ‘anionic’ or ‘nonionic’ surfactant, without research e.g. ‘potassium cocoate’ is anionic, ‘glyceryl cocoate’ is nonionic.

Summary

Surfactants are used in cleaning products to reduce surface tension, helping to wash away oil and grease. There are four main categories of surfactant, ionic (anionic, cationic, and amphoteric) and nonionic. Anionic are the most widely used and potent, but they are associated with skin irritation. Nonionic are also found in many household products, and their main advantage is to not form ‘soap scum’ in hard water.

Very few cleaning products list their surfactants and are not currently compelled to do so by law in either the US or EU.

Instead, ingredient label list the overall blend of surfactants, making it impossible to avoid particularly harsh or allergenic ingredients.

So stick with us for now.  There is change afoot with legislation, but in the meantime, we will only review products that have full ingredient disclosure.  We will give our opinion on these ingredients, and we will tell you how well they clean.

That’s why we’re here!

References

[1] Grand View Research, Inc. (). Surfactants Market Analysis by Product, by Application, and Segment Forecasts To . www.grandviewresearch.com

[2] Falbe, J. (). Surfactants in consumer products: Theory, Technology and Application. Springer Science & Business Media.

[3] Pedrazzani, R., Ceretti, E., Zerbini, I., Casale, R., Gozio, E., Bertanza, G., & Feretti, D. (). Biodegradability, toxicity and mutagenicity of detergents: integrated experimental evaluations. Ecotoxicology and Environmental Safety, 84, 274-281.

[4] Mukhopadhyay, P. (). Cleansers and their role in various dermatological disorders. Indian Journal of Dermatology, 56(1), 2.

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