Sep. 08, 2025
Chemicals
First, an interface is a boundary surface that exists between two substances with different properties, and interfaces exist between liquids and solids, liquids and liquids, and liquids and gases.
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Surfactants enhance performance by performing functions such as washing, emulsifying, dispersing, wetting, and penetrating at this interface.
Interface = a boundary surface that exists between two substances with different properties
Liquid and solid: cup and coffee, machine and lubricant
Liquid and liquid: water and oil
Liquid and gas: seawater and air, soap bubbles
Examples of roles of surfactants
Cleaning ・・・ Removing dirt
Emulsification ・・・ Dispersion ・・ Making unmixable things easier to mix
Wetting / Penetration ・・・ Makes wetting and soaking easier
Nonionic surfactants are used in the largest quantities among surfactants, and their raw materials, such as ethylene oxide, are stably supplied in large quantities.
Nonionic surfactants are surfactants that have hydroxyl groups (-OH) or ether bonds (-O-) as hydrophilic groups that do not dissociate into ions in water.
However, since hydroxyl groups and ether bonds do not dissociate into ions in water, their hydrophilicity is quite weak, so they alone do not have the power to dissolve large hydrophobic groups in water. Therefore, several of these groups come together in one molecule to exhibit good hydrophilicity. This is very different from anionic and cationic surfactants, where only one hydrophilic group is sufficient to exhibit hydrophilicity.
Polyethylene glycol chains are hydrophilic because water bonds loosely to the oxygen atoms of the ether bonds in the chain.
When an ether bond is hydrogen bonded to a water molecule, the surrounding water molecules see it as a peer, making it easier to dissolve in water. This is why they are hydrophilic.
In aqueous solutions of polyethylene glycol-type nonionic surfactants, water molecules are loosely attached to the ether bond sites by hydrogen bonds. Therefore, as the temperature rises or salts dissolve into the solution, the hydrogen bonds with the water molecules tend to gradually break off.
When an aqueous solution of a polyethylene glycol-type nonionic surfactant is heated and the temperature is gradually increased, the bound water molecules are gradually dislodged accordingly, resulting in a gradual decrease in hydrophilicity, and finally the surfactant is no longer soluble in water and precipitates, turning the initially clear solution into a cloudy emulsion.
Thus, when a clear aqueous solution of polyethylene glycol-type nonionic surfactant is gradually heated, the temperature at which the entire solution suddenly becomes cloudy and the surfactant precipitates as fine droplets is called the cloud point.
If the hydrophobic group materials are the same, the cloud point will also increase as the hydrophilicity increases with an increase in the number of moles of ethylene oxide added, and this cloud point can be used as a value representing the hydrophilicity of the nonionic surfactant.
The cloud point can be understood as an indication of how strong the hydrophilicity of the polyethylene glycol moiety attached to the hydrophobic group is compared to the strength of the hydrophobic group.
The effect of a surfactant is originally derived from the balance between the opposing properties of the hydrophobic and hydrophilic groups, and the cloud point, which indicates the degree of this balance, is the most important value that determines the properties of polyethylene glycol-type nonionic surfactants.
In fact, quality control of this type of surfactant and guidelines for its use are based on the measurement of the cloud point. For example, it is generally accepted that a surfactant with a cloud point near the operating temperature has excellent permeability. However, the presence of salts or alkalis such as sodium hydroxide causes the cloud point to drop dramatically, so in such cases, it is necessary to measure the cloud point under operating conditions to make a judgment.
Among alkylphenol EO adducts, nonylphenol, dodecylphenol, octylphenol, octylcresol, and other EO adducts are known.
Among them, nonylphenol EO adducts have been the mainstay of polyethylene glycol ether-type nonionic surfactants because of their superior detergency, penetration, and emulsifying power.
However, alkylphenols have been found to have endocrine disrupting effects, and the use of alkylphenol EO adducts has been declining as they are being replaced by alternative surfactants.
Natural alcohols have been replaced by synthetic alcohols for some time due to their generally high price volatility, but their use is now increasing due to environmental concerns and other factors. Generally speaking, C12~C14 alcohols are more suitable as surfactant raw materials than C16~C18.
The most typical saturated natural alcohol is palm oil-reduced alcohol (C12~C14), which is obtained by esterifying palm oil with methanol and reducing the resulting methyl palm oil fatty acid.
Unsaturated alcohols include palm oil alcohol and olive oil alcohol, which are obtained in a similar fashion from palm oil and olive oil, respectively. Both are mixtures of oleyl alcohol (CI8 double bond 1) and cetyl alcohol (C16), among others.
Beef fat reducing alcohol (C16~C18) obtained by hydrogenating methyl bovine fatty acid and macko alcohol (C16-C18 double bond 1) obtained by hydrogenating macko whale oil were also used, but are rarely used anymore due to the avoidance of using animal materials and the protection of whale resources. However, it is rarely used anymore due to the avoidance of using animal materials and the protection of whale resources.
It is made through the process of ethylene polymerization by the Ziegler process. It has a chemical structure (linear primary alcohol) identical to that of saturated natural alcohols.
The reaction of olefin with carbon monoxide and hydrogen yields a primary alcohol with one more carbon atom (oxo method). Although there are some special olefins that use branched-chain olefins such as the trimer and tetramer of propylene as the raw material olefin, the most common method uses linear-chain α-olefins, which are mainly linear primary alcohols like natural alcohols, with some branched primary alcohols mixed in.
Since ester bonds are susceptible to hydrolysis, this type of product may decompose into soap when used in strongly alkaline baths. This type of soap is also produced by addition of ethylene oxide as described above, but can also be easily produced by direct esterification of fatty acids with polyethylene glycol.
Polyoxyethylene fatty acid esters are generally inferior to higher alcohols or alkylphenol EO adducts in terms of penetration and detergency. Therefore, they are mainly used as emulsion dispersants, textile oils (for spinning and finishing), or dyeing auxiliaries.
To strengthen its characteristics as an oil-soluble emulsifier, polyethylene glycol is added to fats and oils such as olive oil and an alkali-catalyzed ester exchange reaction is performed to make a mixture of polyethylene glycol monooleate and glycerin monooleate, which is also widely used.
However, most are used as raw materials for blending and are not commercially available.
Ethylene oxide can be added also to higher alkylamines or fatty acid amides in the presence of alkaline catalyst.
Higher alkyl amines react particularly easily with ethylene oxide, so the reaction can be carried out without a catalyst. In such cases, the polyethylene glycol chain grows after the complete addition of two moles of ethylene oxide to the nitrogen atom first. This type of product has properties intermediate between those of nonionic and cationic surfactants and is used as a dyeing aid.
Fatty acid amides are relatively unreactive with ethylene oxide and usually react as in the following equation, but in reality they are a complex mixture of reactants. In the usual synthesis process, exchange reactions occur during the reaction and the ester and amide bonds are interchanged, resulting in the formation of some of the following compounds, which are nonionic surfactants with somewhat cationic properties. This type of surfactant is used for special applications and is used in relatively small quantities.
A compound similar to ethylene oxide is propylene oxide.
Propylene oxide reacts by addition in the same way as ethylene oxide. However, its polymerization product, polypropylene glycol, has a limited water solubility; it is soluble in water up to a molecular weight of several hundred, but insoluble with molecular weight beyond that range. Therefore, polypropylene glycol with a molecular weight of about 1,000 to 2,500 is suitable as a hydrophobic group raw material.
Nonionic surfactants made by adding ethylene oxide to polypropylene glycol were first marketed by the Wyandotte Company in the United States under the trade name "Pluronic" and are therefore called Pluronic-type nonionic surfactants. and are therefore referred to as pluronic nonionic surfactants.
Pluronic-type nonionic surfactants have an unusual shape with hydrophilic groups at both ends with hydrophobic groups in between, as shown in the following formula. Since this type of surfactant has a molecular weight of several thousand, it is much higher in molecular weight than ordinary surfactants (molecular weight of several hundred), so it is sometimes classified as a polymer type surfactant.
Pluronic-type nonionic surfactants are not very promising as penetrating agents due to their molecular weight or molecular shape, but they are used in special applications due to their recognized characteristics as special low-foaming detergents, emulsifying dispersants, viscose additives, and the like.
Nonionic surfactants with hydrophobic groups attached to amino alcohols (e.g., diethanolamine) having -NH2 or >NH groups in addition to -OH groups or to saccharides (e.g., glucose) having 1CHO groups are similar to the polyhydric alcohol type. Therefore, they are collectively referred to as polyhydric alcohol-type nonionic surfactants in this section.
The main hydrophilic group materials of polyhydric alcohol-type nonionic surfactants are listed in the table below. Of these, glycerin, pentaerythritol, sorbitan, and diethanolamine are particularly important. Fatty acids are the most commonly used hydrophobic raw materials.
As shown in the table below, many polyhydric alcohol-type nonionic surfactants are not soluble in water, and most are only hydrophilic enough to be emulsified and dispersed in water. Therefore, they are rarely used as detergents or penetrating agents.
The appearance of polyhydric alcohol esters is similar to that of fats, oils, or fatty acids, and they are light yellow solids. Both glycerol esters and pentaerythritol esters are widely used as emulsifiers or raw materials for textile oils (spinning oil or softener), but there are differences in their detailed properties.
Fatty acid esters of glycerin
Glycerol monolaurate or glycerol monostearate is widely used as an emulsifier in food and cosmetics because of its high safety, and especially the technology to produce high-purity products has been developed. They are also used as oils for textiles, but their characteristics as fabric softeners are limited to relatively specialized applications.
Sorbitol is a sweet-tasting polyhydric alcohol produced by reducing glucose with hydrogen and has six hydroxyl groups.
Since sorbitol has no aldehyde groups in its molecule, it is more stable to heat and oxygen than glucose, and there is no risk of decomposition or coloration when reacting with fatty acids.
Sorbitol esters are suitable for textile softeners, but do not work well as general W/O emulsifiers.
Sorbitan is a polyhydric alcohol with four hydroxyl groups, but various isomers are formed depending on the position of the hydroxyl group that reacts when sorbitol is dehydrated. Therefore, what is commonly called sorbitan is a mixture of various sorbitans, not a compound with a single composition. Sorbitan is further dehydrated and has only two hydroxyl groups. In fact, when sorbitol is dehydrated, the reactions shown above occur in a complex manner to produce a mixture of many compounds. Therefore, these sorbitol dehydration products are sometimes collectively called anhydrosorbitols.
When the esterification reaction of sorbitol is carried out at 230-250°C, intramolecular dehydration (sorbitanation) of sorbitol also occurs at the same time. If the reaction is stopped after an appropriate time, monopalmitate esters of sorbitan can be obtained in one step.
If the reaction is further continued to proceed with intramolecular dehydration, a product consisting mainly of the sorbitan ester can be obtained.
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Featured content:Sorbitan esters have excellent performance as emulsifiers and textile oils.
Sorbitan ester-type nonionic surfactants are so well known that they are called "spun-type nonionic surfactants" since they were first marketed by Atlas Corporation in the United States under the trade name "Span" (Span) in various varieties.
These sorbitan esters are mainly used as emulsifiers, but since they themselves are almost insoluble in water, they are rarely used alone.
Fatty acid esters of polyhydric alcohols and sugars are susceptible to hydrolysis. Instead of these esters, those linked by amide bonds are surfactants that are also resistant to hydrolysis. Many polyhydric alcohol-type nonionic surfactants with amide bonds have been synthesized by combining fatty acids with compounds that have amino and hydroxyl groups.
The most prominent of these polyhydric nonionic surfactants with amide bonds is fatty acid alkanolamide, which is synthesized by the condensation of alkanolamine and fatty acids.
Fatty acid alkanolamides were first marketed by the U.S.-based Ninol Corporation and were therefore also called "Ninol-type detergents. This is the product of dehydration-condensation of 1 mole of lauric acid or palm oil fatty acid with 2 moles of diethanolamine.
Although this formula may seem to leave an extra mole of diethanolamine, the extra diethanolamine is actually loosely bound to the produced lauric acid diethanolamide, making the resulting fatty acid alkanolamide very water soluble.
It is also called 1:2 fatty acid diethanolamide because it is produced at a ratio of 2 moles of diethanolamine to 1 mole of fatty acid.
The detergency-enhancing and foam-stabilizing effects of 1:2 fatty acid alkanolamides described above are caused by their main component, the fatty acid alkanolamide, and have little to do with the second mole of diethanolamine. Therefore, when added as a foam stabilizer to a highly water-soluble detergent, such as sodium dodecylbenzenesulfonate, the extra diethanolamine is unnecessary, as it is added simply to provide water solubility.
From this perspective, 1:1 type fatty acid diethanolamides without the second mole of diethanolamine were produced for compounding. Lauric acid or coconut oil fatty acid is still used as the fatty acid, but it is usually made into a methyl ester to facilitate the reaction.
This one is widely used as a base for detergent formulations because of its high purity and economic efficiency. A 1:1 type alkanolamide is also made from monoethanolamine and monoisopropanolamine and used for similar purposes.
Of the raw materials shown in this table, ethylene oxide is produced inexpensively due to the development of petrochemistry. In addition to those derived from natural products, a wide variety of synthetic higher alcohols have also appeared on the market.
Furthermore, considering the excellent performance and versatility of polyethylene glycol-type nonionic surfactants, this type of product is likely to become increasingly important in the future.
In addition to those listed in the table above, there are also higher alkyl mercaptans (R-SH) as hydrophobic group materials and dipentaerythritol and polyglycene as hydrophilic group materials, but these are omitted in this section.
Reference: "Introduction to Surfactants" by Takehiko Fujimoto, Sanyo Kasei Kogyo ()
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Trying to avoid SLS and other harsh surfactants in your cosmetics? There are many mild, natural surfactants available. Learn about the different types of natural surfactants, with a list of my favorites.
There are many types of surfactants and they are used for many different purposes, but they all share one quality: they help increase the wetting properties of a liquid. Surfactants can be found almost everywhere. You can find them in everything from detergents and shampoos to toothpaste and even conditioners.
(A surfactant,) also called surface-active agent, (is a ) substance such as a detergent that, when added to a liquid, reduces its surface tension, thereby increasing its spreading and wetting properties. (Encyclopaedia Britannica)
Some surfactants are emulsifiers, others are foaming agents (and some may actually do the opposite of those functions). Some act as detergents, while others act as insecticides or fungicides. Some help with solubilizing (small amounts of oils into water, for example) and others help increase viscosity.
Surfactants affect the surface tension of liquids to increase wetting.
Normally, when you spray water on a surface like a window, rather than spread evenly over the surface, the water will bead up. That’s because of the surface tension of the water. The molecules of the water come together in a stable configuration and are attracted to each other. When you are trying to clean that window, though, that beading isn’t helping you. You want the water to spread evenly over the surface to better clean it. You also want something that can grab onto the grease and dirt on whatever surface you are trying to clean.
Surfactants affect the surface tension that is making the water bead up rather than spread out. They have a water-loving head and an fat (oil) loving tail. They come together in structures called micelles.
I already explained a bit about how the micelles in surfactants work in my micellar water recipe, but for those who haven’t read that post, let me give you a quick, simplified explanation. The water-loving heads of the micelles bond with the water while the oil-loving tails on the inside of the micelles bond with the grease and grime. That pulls the grease and grime into the center of the micelles out of contact with the water, making them easier to rinse away.
You’ll also find that hot water helps clean better because the hot water helps melt the fats which makes it easier for them to be brought into the micelles.
There are four main types of surfactants, each behaving somewhat differently, and some with completely different functions. The detergent-like surfactants tend to be the anionic, non-ionic and amphoteric surfactants. Some cationic surfactants are used as emulsifiers and are great for hair conditioners. (I use BTMS, a cationic surfactant, in my hair conditioner recipe.)
These are classified based on the charge of the polar head of the surfactant which can have a positive charge (cationic), a negative charge (anionic), or no charge (non-inonic). Amphoteric surfactants have both a cationic and anionic part attached to the same molecule.
Natural surfactants can be derived from many types of plants. Common sources are coconut or palm, but they can also be derived from other types of fruits and vegetables.
There are many natural surfactants on the market today, and with increased consumer demand, I imagine that many more will be available in time. I have tried many of them, but today I’ll focus on some of my favorites. I like these surfactants because they are gentle, they tend to be easier to find, and they work well together. You can use these in everything from gentle shampoos to shower gels, facial cleanser, and baby washes.
Keep in mind that many of these surfactants are not palm free, so you’ll want to source them from places that allow for sustainable methods of obtaining their materials. I buy surfactants that have been certified sustainable by RSPO (Roundtable on Sustainable Palm Oil) standards.
Another thing to keep in mind is that these surfactants can differ from manufacturer to manufacturer. The names are polymeric and aren’t referring to an exact structure. Some places will use different plants as the origin of elaborating each surfactant, and the way each surfactant cleans, solubilizes, etc. can vary depending on where you buy it from. I’ll be describing these surfactants based on my suppliers, but you’ll want to check on the specifications of the surfactant you are buying if it’s important to you to know what plants have been used to derive them, the pH, the concentration, etc. Use this list as a general guideline!
Along those lines, while mine are listed as ECOCERT approved, that may also be dependent upon the manufacturer of each surfactant.
I’ll be updating this list and adding more surfactants as I use them and learn more about them. For now, though, this should give you a good starting point to understanding what we are going to be working with.
Coco Glucoside is a non-ionic surfactant that is obtained from coconut oil and fruit sugars, but it can also be obtained from either potato or corn. It is a very gentle, foamy cleanser and is completely biodegradable. You can use it in products that you want to have an ECOCERT certification. It has an alkaline pH (around 12) which makes it self-preserving as is, but you will probably have to adjust the final pH of products using it to pull it into a range more suitable for your skin or hair (and you’ll need to add a preservative).
Decyl Glucoside is very similar to coco glucoside (non-ionic and ECOCERT compatible), but it has a shorter chain length. It creates less foam (its foam is less stable) than coco glucoside but it does add more viscosity to a product. It is derived from coconut oil and glucose and is completely biodegradable. It can be used in all sorts of shampoos, gels, baby products, etc.
Lauryl Glucoside is very similar to the other 2 glucosides I’ve mentioned. It has a longer chain length and more viscosity. It takes longer to foam than the other two, but it also has the most stable foam. While it is also a mild cleanser, it isn’t as mild as the other 2 alkyl polyglucosides.
Disodium Laureth Sulfosuccinate is a gentle anionic surfactant that can be used in natural products (ECOCERT). It is a great alternative to SLS for a milder, more natural shampoo (or body wash, etc.). It has larger molecules than some of the other surfactants (like SLS) making it unable to penetrate and irritate the skin in the same way. It cleans and provides foam in products made for people with sensitive skin.
Coco betaine is a coconut based amphoteric surfactant. It’s mild and can help boost foam and increase the viscosity of products made with it. It’s very mild and provides for gentle cleansing. It’s completely biodegradable and has a pH around 6-8. It is also ECOCERT compatible so it can be used in the elaboration of “natural” and “organic” type products.
Sodium coco sulfate is an anionic surfactant that is ECOCERT and BDIH friendly. It has a pH of 10-11 and is derived from coconut oil. It is a water-soluble surfactant that is sold in solid form. It’s usually used in non-soap shampoo bars and/or bar cleaners (syndet bars).
Plantapon SF is a mix of vegetable-based surfactants (coconut, corn, and palm based) that can be used in a variety of gentle cleansing products like shampoos, shower gels, and facial cleansers. It includes sodium cocoamphoacetate, lauryl glucoside, sodium cocoyl glutamate, sodium lauryl glucose carboxylate, and glycerin. It has a pH between 6.5 and 7.5.
Because this is a mix of surfactants, it can be a good choice for those who are just delving into working with surfactants. You can easily mix up formulations without needing to buy a lot of raw materials or doing a lot of work. (I’ll work on getting up some recipes that use this as soon as I can.)
While not as effective as the other more processed surfactants derived from natural sources, those looking for a completely natural alternative may be interested in studying some of these natural surfactants. These plant based cleansers all have natural saponins that are a type of non-ionic surfactant. They can be used alone or combined with the other surfactants for a more effective final product.
The fruits taken from the sapindus trees/shrubs from the lychee family have saponins which are natural non-ionic surfactants. They are usually called either soap nuts or soap berries, and they clean without creating much foam.
You can either throw a cloth bag of them in with your laundry to naturally wash your clothes, or you can steep them in warm water to extract a liquid that can be used for cleaning. Make just enough for what you’ll need and you can freeze the rest.
Liquid yucca extract is a natural non-ionic surfactant that comes from the yucca plant, a desert plant that has natural saponins of its own. While you can add it to your homemade shampoos, yucca extract is also used in gardening to help get nutrients to the roots of other plants by washing away concentrated salts that build up.
Shikakai powder is another plant with natural saponins which are natural non-ionic surfactants. It is normally used in hair care as a very natural “shampoo.” It naturally has a low pH which makes it ideal for hair care. It’s said to be good for all hair types, especially those that are prone to breakage and damage. Like with the other natural surfactants, you can either combine it with other surfactants or use it on its own. To use it on its own, you make a paste by mixing the powder with warm water and running it through your wet hair once it the paste has cooled. You then leave it to act for 10-15 minutes before rinsing it out. It may slightly darken hair.
Soapwort is another plant that has been used for many years as a soap alternative. It can be used to clean the skin, wash your hair, or even as a laundry soap. It’s especially good for delicate fabrics. To use soapwort, you need to make an infusion of the soapwort in water, and then you can use the resulting liquid as a liquid soap alternative.
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