Selecting the Right Surfactant for Cosmetics

13 May.,2024

 

Selecting the Right Surfactant for Cosmetics

Surfactant Applications and Key Benefits



What are Surfactants?

Whoever said oil and water can’t mix had perhaps never heard of surfactants. A surfactant or a surface-active agent is a compound that lowers the surface tension at the interface of two liquids, a liquid and a gas or a liquid and a solid. It has an amphiphilic molecular structure which means that the molecule is water-loving (hydrophilic) at one end and fat-loving (lipophilic) at the other. The surfactant molecules align themselves such that their hydrophilic groups (heads) are in the water phase whereas the lipophilic end (tails) extend out into the oil or gas (usually air) phase. Surfactants are classified as follows based on the charge of the head group.

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  • Anionic Surfactants:

    The head group has a negative charge
  • Cationic Surfactants:

    The head group has a positive charge
  • Amphoteric Surfactants:

    The head group may simultaneously carry both anionic and cationic hydrophilic groups. Cations or anions are formed depending on ambient conditions such as pH.
  • Non-ionic Surfactants:

    The head group carries no charge





Surfactant Applications in Cosmetics

Detergency

Surfactants are an essential part of all cleansing formulations. Dirt can bind to skin and hair through natural skin oils or oily contaminants picked up from the environment. Surfactants combine oil and water to lift the contaminants off the surface which can then be washed away with water. The choice of a suitable surfactant depends on the preferred chemistry, method of delivery, and desired user experience.

Wetting

Wetting is the ability of a liquid to spread on a solid surface. Products with poor wetting properties tend to ball up on the surface. Surfactants also act as wetting agents, making the product easier to spread while also helping lift oil from the surface for removal. Surfactants are incorporated as wetting agents in the formulation of creams and lotions.

Foaming

Bubbles are formed when air is incorporated into a liquid as a result of working the product on the skin or hair. A small amount of surfactant, added to a product, reduces surface tension between the liquid and air phases thereby reducing the work needed to generate foam. The surfactant also increases the stability of the foam by inhibiting the coalescence of bubbles. Although foaming does not contribute to dirt removal, it is an important part of a pleasing user experience.

Emulsification

Creams and lotions are formulated to deliver beneficial lipid (oily) materials to skin or hair. The lipid material is combined with water and other ingredients to formulate an easy-to-apply product. Surfactants are used as emulsifiers to produce semi-stable oil-in-water (lotions) or water-in-oil emulsions (creams).


Choosing the best surfactants

Surfactants are an essential part of all cleansing formulations. Dirt can bind to skin and hair through natural skin oils or oily contaminants picked up from the environment. Surfactants combine oil and water to lift the contaminants off the surface which can then be washed away with water. The choice of a suitable surfactant depends on the preferred chemistry, method of delivery, and desired user experience.Wetting is the ability of a liquid to spread on a solid surface. Products with poor wetting properties tend to ball up on the surface. Surfactants also act as wetting agents, making the product easier to spread while also helping lift oil from the surface for removal. Surfactants are incorporated as wetting agents in the formulation of creams and lotions.Bubbles are formed when air is incorporated into a liquid as a result of working the product on the skin or hair. A small amount of surfactant, added to a product, reduces surface tension between the liquid and air phases thereby reducing the work needed to generate foam. The surfactant also increases the stability of the foam by inhibiting the coalescence of bubbles. Although foaming does not contribute to dirt removal, it is an important part of a pleasing user experience.Creams and lotions are formulated to deliver beneficial lipid (oily) materials to skin or hair. The lipid material is combined with water and other ingredients to formulate an easy-to-apply product. Surfactants are used as emulsifiers to produce semi-stable oil-in-water (lotions) or water-in-oil emulsions (creams).

Many companies offer a wide range of surfactants to meet the diverse requirements of various types of cosmetic formulations. The different range includes cationic, anionic, amphoteric, and non-ionic surfactants suitable for all major cosmetic applications.



Some important features of high-quality surfactants:

Low irritancy

Harsh surfactants interact with proteins and lipids in the outermost layer of the skin, called the stratum corneum. They may cause this protective barrier to break down leading to redness, irritation, dryness, and itching. Anionic surfactants generally offer the best foaming and cleansing properties for cosmetic applications but they are also the harshest towards human skin.

Narrow Range Ethoxylation:

Narrow-range ethoxylation can obtain alkylene oxide adducts having a narrow distribution of the number of alkylene oxide adduct moles.

Excellent foaming properties

Foams are generally easier to generate and maintain under alkaline conditions. As the pH is lowered, the foam-forming potential of surfactants is reduced. An ideal surfactant gives good foaming properties even in a weak acidic medium. The surfactants should be able to generate stable, fine, rich, and soft foams suited to various applications.

Easily bio-degradable

With the advancement of the cosmetics industry following the sustainable trends, the surfactants should be easily bio-degradable which can help cosmetics manufacturers formulate products that are eco-friendly and sustainable.

Harsh surfactants interact with proteins and lipids in the outermost layer of the skin, called the stratum corneum. They may cause this protective barrier to break down leading to redness, irritation, dryness, and itching. Anionic surfactants generally offer the best foaming and cleansing properties for cosmetic applications but they are also the harshest towards human skin.Narrow-range ethoxylation can obtain alkylene oxide adducts having a narrow distribution of the number of alkylene oxide adduct moles.Foams are generally easier to generate and maintain under alkaline conditions. As the pH is lowered, the foam-forming potential of surfactants is reduced. An ideal surfactant gives good foaming properties even in a weak acidic medium. The surfactants should be able to generate stable, fine, rich, and soft foams suited to various applications.With the advancement of the cosmetics industry following the sustainable trends, the surfactants should be easily bio-degradable which can help cosmetics manufacturers formulate products that are eco-friendly and sustainable.

The other benefits can be low odor, prevention of excessive de-greasing, excellent solubility and detergency, compatibility with other surfactants, non-neutralized products, and compliance with safety and health regulations.

An Easy Guide to Understanding How Surfactants Work | IPC

An Easy Guide to Understanding How Surfactants Work

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What is a Surfactant?

Surfactants are a primary component of cleaning detergents. The word surfactant means surface active agent. As the name implies, surfactants stir up activity on the surface you are cleaning to help trap dirt and remove it from the surface.

Surfactants have a hydrophobic (water-hating) tail and a hydrophilic (water-loving) head. The hydrophobic tail of each surfactant surrounds soils. The hydrophilic head is surrounded by water.

How do surfactants work?

When there are a sufficient amount of surfactant molecules present in a solution they combine together to form structures called 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 of the structure protected from water.

The micelles work as a unit to remove soils.  The hydrophobic tails are attracted to soils and surround them, 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.

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Types of Surfactants

The hydrophilic head of each surfactant is electrically charged. The charge can be negative, positive, or neutral. Depending on the charge of the hydrophilic head, the surfactant is classified as anionic, nonionic, cationic or amphoteric.

Anionic Surfactants

Anionic surfactants have a negative charge on their hydrophilic end. The negative charge helps the surfactant molecules lift and suspend soils in micelles. Because they are able to attack a broad range of soils, anionic surfactants are used frequently in soaps and detergents. Anionic surfactants create a lot of foam when mixed. While anionic surfactants are excellent for lifting and suspending particulate soils, they are not as good at emulsifying oily soils.

Sulfates, sulfonates, and gluconates are examples of anionic surfactants.

Nonionic Surfactants   

Nonionic surfactants are neutral, they do not have any charge on their hydrophilic end. Nonionic surfactants are very good at emulsifying oils and are better than anionic surfactants at removing organic soils. The two are frequently used together to create dual-action, multi-purpose cleaners that can not only lift and suspend particulate soils, but also emulsify oily soils.

Certain nonionic surfactants can be non-foaming or low-foaming. This makes them a good choice as an ingredient in low-foaming detergents.

Nonionic surfactants have a unique property called a cloud point. The cloud point is the temperature at which the nonionic surfactant begins to separate from the cleaning solution, called phase separation. When this occurs, the cleaning solution becomes cloudy. This is considered the temperature for optimal detergency. For low foaming cleaners, optimal detergency is at the cloud point; for foaming cleaners optimal detergency is either just below the cloud point or at the start of the cloud point. The agitation of low foaming cleaners is sufficient to prevent phase separation.

The temperature of the cloud point depends upon the ratio of the hydrophobic and hydrophilic portions of the nonionic surfactant. Some cloud points are at room temperature while others are very high. Some nonionic surfactants don’t have a cloud point because they have a very high ratio of hydrophilic to hydrophobic moieties.

Examples of some common nonionic surfactants include cocamide, ethoxylates, and alkoxylates.

Cationic Surfactants

Cationic surfactants have a positive charge on their hydrophilic end. The positive charge makes them useful in anti-static products, like fabric softeners. Cationic surfactants can also serve as antimicrobial agents, so they are often used in disinfectants.

Cationic surfactants cannot be used with anionic surfactants. If positively charged cationic surfactants are mixed with negatively charged anionic surfactants, they will fall out of solution and no longer be effective. Cationic and nonionic surfactants, however, are compatible.

Examples of some common cationic surfactants include alkyl ammonium chlorides.

Amphoteric Surfactants

Amphoteric surfactants have a dual charge on their hydrophilic end, both positive and negative. The dual charges cancel each other out creating a net charge of zero, referred to as zwitterionic. The pH of any given solution will determine how the amphoteric surfactants react. In acidic solutions, the amphoteric surfactants become positively charged and behave similarly to cationic surfactants. In alkaline solutions, they develop a negative charge, similar to anionic surfactants.

Amphoteric surfactants are often used in personal care products such as shampoos and cosmetics. Examples of some frequently used amphoteric surfactants are betaines and amino oxides.

How Surfactants are used in Cleaners

Surfactants are a key ingredient in cleaning products. One thing that differentiates cleaning products is how they are made. Cleaners made from a single chemical, targeting a specific type of soil, are referred to as commodity cleaners. Cleaners that are blends of various chemical ingredients designed to work together to remove various types of soils are referred to as formulated cleaners.

Formulated cleaners usually contain four basic elements: surfactants, hydrotropes, builders and carriers. Hydrotropes are chemicals that keep the otherwise incompatible surfactants and builders stable in a solution. The carrier is either water or a solvent. These elements work together to create mechanical actions to remove soils. The end result is a product that can attack dirt on surfaces with a variety of cleaning mechanisms including emulsifying, lifting, dispersing, sequestering, suspending and decomposing soils of various types. The type of surfactants used in a cleaning product largely determines which soils they will be best at removing.

IPC offers a full line of formulated cleaners that among the safest yet most effective solutions on the market. Request a free sample to test our products for your most challenging cleaning applications.

For more information, please visit China Phosphoric Ester.

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