Last Updated on March 6, 2023 by Verna Meachum
If you’re anything like me, then the ingredient Behentrimonium Chloride and Cetrimonium Chloride probably doesn’t mean all that much to you.
It’s one of those long, scientific words that seems to get tossed around in hair product descriptions without a whole lot of explanation.
But what does it actually do? And more importantly, what does it do for your hair?
Keep reading to find out!
Overview
Hair conditioners are designed to improve the quality of hair fiber. Their objective is to align hair cuticles, reduce hair surface friction and restore the natural outlook of hair fibers.1
Cationic conditioning agents are the main key ingredient used in almost every conditioning formulation.
Among them, Behentrimonium Chloride and Cetrimonium Chloride are two major and most abundantly used conditioning agents. You can find them in the label INCI listing in almost every type of conditioner.
Besides these two, a wide range of other similar conditioning agents can also be used in a formulation.2
In the summary below, let’s examine their chemistry, their function in a formulation, and their beneficial properties in boosting hair quality.
A list of similar cationic ingredients is also drafted below for a broader understanding.
First, let’s look at the major benefits they impart to hair fibers.
Major Benefits of Using Behentrimonium and Cetrimonium Chlorides
✓ Hair softness
✓ Improve hair surface quality
✓ Aligns hair cuticles
✓ Anti-static agent
✓ Ease in dry and wet combing
✓ Detangles hair fibers
Quaternary Ammonium Salts, Alkyltrimethylammonium Chloride
Behentrimonium chloride and Cetrimonium Chloride belong to the family of Quaternary Ammonium Salts.
“Quaternary Ammonium Salt” is a technical term representing a group of positively organic compounds.
They are also known as Alkyltrimethylammonium Chlorides (For simple illustration can be written as Alkyl – trimethyl – ammonium Chlorides).
Examples of Alkyltrimonium Chlorides
- Cetrimonium Chloride
- Steartrimonium Chloride
- Stearalkonium Chloride
- Behentrimonium Chloride
- Dicetyldimonium Chloride
- Distearyldimonium chloride
There are two characteristic structural features of these molecules:
- Positively charged nitrogen group attached to three methyl carbons
- Long hydrophobic carbon chain
The molecular structure demonstrates a long carbon chain attached to the quaternary nitrogen group carrying a partial positive charge.
The electrostatic charge on the nitrogen group is stabilized by counter ions of chloride forming a quaternary salt.
The nitrogen group has a positive charge that is a vital component of its molecular structure because this conditioner binds itself to negatively charged amino acids of the hair fiber.
The length of the carbon chain attached varies and different versions of Alkyltrimethylammonium chlorides are available to the formulators.
The nature of the hydrophobic carbon chain and its length greatly influences the conditioning performance.
Experimental data suggest that conditioning agents that have longer carbon chains perform better and offer superior hair slip and conditioning.
Cetrimonium chloride contains 16 carbons attached to a chain, while Behentrimonium chloride has 22 carbons attached.
Therefore, Behentrimonium chloride has a longer alkyl carbon length and offers more lubricity and conditioning than Cetrimonium chloride.
Moreover, long carbon chain compounds are water-insoluble due to higher hydrophobicity.
Cetrimonium Chloride is water-soluble while Behentrimonium chloride is a water-insoluble wax.
Conditioning Mechanism
Electrostatic bonding
Hair is a protein fiber having a varying amount of different amino acids that constitutes the whole structure of hair fiber.
Amino acids carry both positive and negative charge points in their molecular structure.
Therefore, they have an electrical tendency to attach to other molecules via electrostatic bonding.
Experimental studies reveal hair isoelectric point to be 3.70. This describes that hair below pH 3.70 carries a positive charge, while the same hair above the 3.70 pH level demonstrates an anionic character having negative charges.
Furthermore, hair proteins undergo degradation via oxidation reactions during everyday grooming, photo-bleaching, and various cosmetic treatments.
This generates negatively charged sites on amino acid residues all over the hair shaft.
During oxidative bleaching and exposure to UV rays, the disulfide bond is broken and cystine amino acid is oxidized to cystic acid.3
Hair becomes extremely negatively charged and highly hydrophilic. That’s why there is a higher negative charge density on damaged hair fibers compared to healthy hair.
Positive charges attract negative charges.
Both Behentrimonium Chloride and Cetrimonium Chloride carry positive charge density over their nitrogen group (as described earlier).
These positively charged conditioning agents get attached to negatively charged amino acid sites over the hair surface via the electrostatic chemical bond.
The long hydrophobic carbon chain is now attached to hair fiber via this chemical bond and thus provide lubricity and conditioning on the hair surface.
The longer the carbon chain length, the higher the conditioning potential and lubricity.
Van Der Waals Interactions
A second chemical interaction between cationic conditioning agent and hair surface is via Van Der Waals forces.
This chemical bonding exists between the long hydrophobic carbon chain and carbon sites of hair proteins.
This is weak bonding, yet it plays a role in hair conditioning.
The longer the carbons chain of alkyltrimethyltrimonium chloride, the stronger the Van Der Waals bonding.
This supports the experimental results for Behentrimonium chloride being a better hair conditioner than Cetrimonium chloride due to its longer carbon chain.
Multifunctional Role in a Formulation
Conditioning agent
Alkyltrimonium Chlorides are the key ingredient in hair conditioning formulation and their main function is to condition hair fibers.
When you examine the ingredients list (INCI listing) for any conditioner, they are usually listed among the first five ingredients. This emphasizes their major role in hair conditioning formulations.
Anti-static agent
These quaternary conditioning agents also work as anti-static agents. No one likes static-y hair!
Static leads to frizzy hair which leads to hair becoming difficult to manage and style.
Posititively charged Behentrimonium chloride and Cetrimonium chloride have the ability to counter this static charge by balancing out the net charge density on hair.
Product Rheology and Viscosity
In addition to their conditioning benefits, these cationic molecules have other functions and roles in a formulation.
Most noticeably, they work as an emulsifier and form oil-in-water emulsions for hair conditioners, deep conditioners, curling creams, etc.
They stabilize emollients, natural oils, butter, and waxes in the water phase system.
They also boost the viscosity of the product and deliver a special sensorial feel during product application.
Takeaway
Both Behentrimonium and Cetrimonium Chlorides are the key ingredients of hair conditioning formulations.
Carrying a positive charge, they form electrostatic chemical bonding with hair amino acids.
They are multifunctional ingredients offering multiple benefits to the hair fiber.
These conditioning agents detangle hair fibers, add slip and lubricity to the hair surface and make it easy to comb.
Related Article
Resources
1. Marsh, J. M.; Gray, J.; Tosti, A., Healthy Hair. Springer International Publishing: 2015.
2. Schueller, R.; Romanowski, P., Conditioning Agents for Hair and Skin. Taylor & Francis: 1999.
3. Zviak, C., The Science of Hair Care. Taylor & Francis: 1986.
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