Consumers are moving away from ingredients that were once common, making sulfate-free shampoos a major challenge when formulating.
Your formulation team knows about surfactants. But do they truly understand the implications of sulfates beyond lather? What about the growing ethical and health concerns that impact purchasing decisions?
Most brands skim the surface.
Leaders dive into the details.
This article breaks down the chemistry and the controversies. It’s critical information for your next product line.
That’s why your team needs to read it. To lead, not just to clean.
A surfactant, or surface-active agent, is a chemical that helps reduce the surface tension of water, allowing the liquid to more easily absorb into other substances. If the head of the surfactant molecule is hydrophilic and the tail is hydrophobic, it will form small micelles when mixed with water.
In the context of hair products like shampoo, a surfactant allows water to better penetrate the hair’s oils, allowing dirt to be rinsed away more easily.
There are numerous concerns associated with the use of sulfate surfactants in shampoos, shower gels, and other cosmetic products. Evidence suggests they can cause eye and skin irritation with prolonged use. This poses health risks, and since many products containing these ingredients are tested on animals, it also raises ethical issues.
Are sulfates really bad?
What are today’s consumers looking for?
The demand for gentle, biodegradable products suitable for sensitive skin is on the rise. “Sulfate-free” products are becoming increasingly popular.
What alternatives exist to maintain good performance?
Problems in the formulation of sulfate-free shampoos
It is a challenge to find sulfate-free shampoo formulations that deliver the performance and sensory experience customers expect from sulfate-containing products. The most common challenges encountered with sulfate-free formulations are:
Thickened
Sulfate-free surfactants can be difficult to thicken because many of them do not form micelles in the same way as anionic surfactants. They also react poorly to thickeners containing salts. Adjusting the surfactant ratio and/or using a polymer or thickener designed for sulfate-free chassis can be a solution.
Stability of Sulfate-Free Shampoos
Stability can be difficult to achieve because many sulfate-free surfactants will crystallize during stability cycles at cold temperatures. The reaction to salt can also be uneven and cause viscosity issues. Choosing a surfactant with better water solubility and using the best polymer/thickener to stabilize the insoluble material is helpful.
Flow Aesthetics
Sulfate-free surfactants can have a stringy, lumpy rheology/flow due to uneven micelles. This can be addressed by choosing the right thickener/polymer and adjusting usage levels for favorable flow; adjusting surfactant levels and ratios; Ensure that the pH of the final formula matches the recommended pH for the chosen surfactants.
Lack of Clarity
Formulating in certain pH ranges can be challenging, especially for amino-based surfactants. Selecting surfactants with a pH above 5.5 and using a polymer/thickener compatible with the chosen surfactant chassis corrects this problem.
Foam and Sensory Performance
Foam generation of sulfate-free surfactants is poor compared to traditional sulfated surfactants. To improve foam generation, you can choose an amphoteric surfactant or foam enhancer; reduce the levels of oil and/or other foam inhibitors; and add other ingredients that help improve foam.
Some sulfate-free surfactants can be harsh and drying to skin and hair. Choosing a sulfate-free system with performance-enhancing ingredients, such as polymers, esters, and conditioning humectants, will improve foam production. The success and performance of sulfate-free systems depends on the correct combination of rheology modifiers, conditioning agents, and surfactant chassis.
How to thicken sulfate-free shampoos?
While there are several classes of surfactants that are suitable substitutes for sulfated products, the challenge often arises when attempting to increase the viscosity of a sulfate-free system.
This becomes even more difficult when maintaining clarity and achieving viscosity targets without the use of polymeric thickeners is required.
If the use of natural polymers is permitted, the range of available ingredients expands to include gums such as xanthan gum.
However, if specifications are more restrictive, while these requirements would invalidate traditional and popular approaches such as the use of carbomers, cellulose derivatives, or highly ethoxylated materials such as PEG-150 distearate, there are other options available to the formulator.
Those skilled in the art might initially turn to sodium chloride as a thickener, a cost-effective option that can deliver the desired results, depending on the salt sensitivity of the surfactant system. Salt tolerance limits can be easily established by creating a salt curve with the salt contribution of the surfactants included in the totals.
Furthermore, product performance and aesthetics should also be evaluated to determine if the rheological profile is adversely affected to the point of stringiness.
In addition to the selected primary surfactants, the role of secondary surfactants in building viscosity should not be underestimated. Betaines, hydroxysultaines, alkanolamides, and amine oxides are just a few of the chemical classes that have multifunctional benefits, including viscosity enhancement.
Given the current status of mono- and diethanolamines, mono- and diisopropanolamines have proven to be effective substitutes as foam boosters and viscosifiers.
How to choose the best alternative for each formulation?
Increased viscosity
Surfactant ratios also play an important role in maximizing viscosity and should be thoroughly investigated.
Understandably, given tight deadlines, time is not always a luxury the formulator can afford.
Whenever possible, an experimental design should be considered as a tool to identify optimal ratios. Similarly, the order in which surfactants are added can also affect viscosity and should be investigated, as should the system’s response to pH adjustment.
While developing clear, sulfate-free shampoos and body washes without polymeric thickeners may initially seem like a daunting task, there are several formulation and ingredient options available that will allow you to showcase your creative talent.
Some recommended thickener options compatible with systems with sulfate-free and amino acid-based surfactants:
- Hydroxypropyl Starch Phosphate: Natural, easy-to-use, improves the sensory experience and provides good viscosity without affecting foam formation.
- PEG-150 Pentaerythrityl Tetrastearate + PPG-2 Hydroxyethyl Coco/Isostearamide: A reliable combination that provides smooth and stable structures.
- Xanthan Gum or Modified Cellulose Gum (Hydroxyethylcellulose): Natural and compatible ingredients that require proper agitation to avoid clumping.
- Acrylic Copolymers (and derivatives): Offer stability over a wide pH range, ideal if your formula contains acids or active extracts.
- PROBLEND SF 35 by Protécnica Ingeniería: A specialized blend with excellent foaming performance, ensuring effective cleansing while maintaining softness on skin and hair. AKYPO FOAM LM 25: Mild anionic surfactant designed to create a creamy foam with small bubbles and high consistency.
- AMISOFT CS 22: Amino acid-derived surfactant that preserves the integrity of hair and skin during washing, preventing protein denaturation. It promotes sebum-regulating action and effectively reduces pollution and build-up. (Cosmos/Natrue certified)
- AKYPO SUGAR LM 42: An anionic surfactant that maintains all the gentleness and low-irritation properties of nonionic surfactants and has an excellent environmental profile, as it contains 96% renewable carbon. (Cosmos/Natrue certified)
As the disadvantages of SLS and SLES become better understood, new challenges arise that must be addressed when formulating sulfate-free shampoos. Brands are striving to find an alternative ingredient that can effectively thicken their formulas without sacrificing clarity.
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