AES (Fatty Alcohol Polyoxyethylene Ether Sulfate) in Personal and Home-Care Cleansing Formulations: An Analysis of Structure, Performance, and Low-Temperature Flowability

1. Introduction

In the production of cleansing products such as shampoos, body washes, hand soaps, and dishwashing detergents, AES is one of the commonly used primary surfactants. During winter production, many factories encounter a practical problem: after AES arrives, it becomes thickened, forms lumps, cannot be poured out, or cannot be pumped. During dilution, it may also easily form local gel blocks, crystalline agglomerates, or non-uniform high-viscosity regions, affecting unloading, charging, and the overall production schedule.

On the surface, this may look like the material has “frozen” at low temperature. However, from the nature of the product itself, the low-temperature problem of standard high-active AES is not simply caused by water freezing. Rather, it is related to viscosity increase, local crystallization, gelation, or solidification in a high-concentration surfactant–water system at low temperatures. The main difference between standard AES and anti-freeze AES is not their cleansing mechanism, but their low-temperature flowability, convenience in storage and transportation, and suitability for production operations.

2. What Is AES: A Type of Alcohol Ether Sulfate Surfactant

In the personal and home-care industry, AES generally refers to fatty alcohol polyoxyethylene ether sulfate surfactants. A common commercial product is sodium fatty alcohol polyoxyethylene ether sulfate. In cosmetics and personal cleansing products, the common ingredient name is SLES, or Sodium Laureth Sulfate, also known as sodium lauryl ether sulfate or sodium fatty alcohol polyoxyethylene ether sulfate.

The typical structure of AES can be represented as:

R—O—(CH₂CH₂O)n—SO₃Na

Structural Unit	Meaning	Main Influence
R	Fatty alcohol alkyl chain, commonly C12–C14	Detergency, emulsification, foam, low-temperature behavior
(CH₂CH₂O)n	EO, or ethylene oxide, adduct chain segment	Water solubility, compatibility, relative mildness
—SO₃Na	Sodium sulfate ester anionic hydrophilic group	Wetting, foaming, cleansing, salt-thickening response

One end of the AES molecule is lipophilic, while the other end is hydrophilic, making it a typical amphiphilic molecule. This structure enables AES to reduce the surface tension of water and to provide detergency, foaming, emulsification, and dispersion in cleansing systems.

Key factors affecting the performance of AES include:

Key Factor	Influence on Formulation
Carbon chain distribution	Affects detergency, foam, solubility, and low-temperature flowability
Average EO addition number	Affects water solubility, compatibility, thickening response, and low-temperature behavior
Active matter content	Affects dosage, cost, viscosity, and storage/transportation state
Sodium chloride and sodium sulfate content	Affects salt thickening, transparency, and the risk of low-temperature crystallization
Unsulfated matter	Affects odor, foam, transparency, and tendency to precipitate
1,4-Dioxane	As a trace impurity that may be introduced from ethoxylated raw materials, it affects quality control and compliance requirements
Water content and solubilizing system	Affects low-temperature flowability, pourability, and pumpability

3. Structure Determines Performance: Why AES Provides Detergency, Foaming, and Emulsification

3.1 The Hydrophobic Alkyl Chain Provides the Basis for Detergency and Emulsification

The fatty alcohol alkyl chain in the AES molecule is the hydrophobic end, which can easily enter grease, sebum, and dirt. When AES is added to water, the molecules arrange themselves between water and oily soil: the hydrophobic chain approaches the oily soil, while the hydrophilic end faces the aqueous phase. This arrangement reduces the interfacial tension between oil soil and water, making the soil easier to wet, detach, emulsify, and disperse. During washing, the oily soil is dispersed into the aqueous phase and then carried away with the water flow. This is also an important reason why AES can be used in shampoos, body washes, dishwashing detergents, and laundry detergents.

3.2 The EO Chain Improves Water Solubility and Formulation Compatibility

An important difference between AES and SLS, or Sodium Lauryl Sulfate, is that AES contains EO chain segments in its molecular structure. The EO chain generally helps improve the water solubility and formulation compatibility of AES. Compared with non-ethoxylated alkyl sulfates, AES is easier to use in the design of cleansing systems with lower irritation potential. However, the mildness of the final product still needs to be confirmed through dosage control, formulation combination, and irritation evaluation. In shampoos, body washes, and hand soaps, AES is often blended with amphoteric surfactants, nonionic surfactants, conditioning agents, and humectants to balance cleansing power, foam, rinsing feel, and skin feel.

3.3 The Sodium Sulfate Ester Head Group Provides Wetting and Foaming Ability

The sodium sulfate ester head group of AES has strong hydrophilicity and an anionic character. It can effectively reduce the surface tension of water, allowing the cleansing liquid to spread more easily over hair, skin, tableware, or fabric surfaces. The foam performance of AES results from the combined effect of a suitable hydrophobic chain, EO chain, and anionic head group. The sodium sulfate ester head group provides strong hydrophilicity and interfacial activity, while a suitable carbon chain helps the molecules arrange at the gas–liquid interface, thereby forming abundant foam.

4. Micelles Determine Formulation Performance: Why AES Can Be Thickened with Salt

After AES reaches a certain concentration in water, it spontaneously forms micelles. Micelles not only participate in detergency, but also affect the viscosity of the system. For shampoos, body washes, and dishwashing detergents, understanding changes in micelle structure is the key to understanding salt thickening and viscosity changes after raw material substitution.

In AES systems, NaCl, or sodium chloride, is commonly used to adjust viscosity. This is because salt changes the electrostatic interactions and arrangement of micelles. Under low-salt conditions, there is strong electrostatic repulsion between the head groups of AES molecules, micelles are relatively small, and the system viscosity is relatively low. After an appropriate amount of salt is added, the ionic strength increases, the electrostatic repulsion between anionic head groups is partially screened, and micelles are more likely to grow and form entangled structures, resulting in increased system viscosity.

However, salt thickening does not mean that “the more salt, the higher the viscosity.” When the salt level continues to increase, the system may pass the optimal salt point. The micelle structure and hydration state may change, causing the viscosity to decrease instead. In some cases, turbidity, precipitation, or phase separation may occur.

Salt Addition Stage	System Change	Formulation Performance
Insufficient salt	Insufficient micelle entanglement	Low viscosity
Appropriate salt level	Micelles grow and form entanglements	Viscosity increases, and the system is relatively stable
Excessive salt	Micelle structure becomes unstable or hydration capacity decreases	Viscosity decreases, with possible turbidity or precipitation

5. Why Standard 70% AES Becomes Hard at Low Temperatures

Common AES products on the market include high-active products at around 70%, as well as liquid products at around 25%–30%. 70% AES offers high transportation efficiency and lower logistics cost per unit of active matter, so it is widely used in personal and home-care production. However, high active content also means less water in the system and a higher surfactant concentration, making low-temperature flowability problems more likely.

Standard 70% AES is a high-concentration surfactant–water system. At low temperatures, the system may undergo the following changes:

Low-Temperature Change	Production Impact
Significant viscosity increase	Slow pouring and difficult pumping
Local crystallization	Particles, hard lumps, or non-uniform appearance
Gelation	Slower dilution, with local gel blocks or non-uniform high-viscosity regions
Solidification	Drum-packaged raw material becomes difficult to remove
Insufficient recovery after freeze–thaw	Changes in appearance, viscosity, or formulation performance

These phenomena directly affect production: unloading time becomes longer, residue at the bottom of drums increases, dosing errors become larger, and dilution time is extended. In severe cases, batch stability may be affected. The winter problem of standard AES is essentially a flowability and phase-state issue of a high-concentration surfactant system at low temperatures.

When addressing these problems, simple heating alone should not be relied upon, and localized high-temperature forced heating should be avoided. In actual operation, mild and uniform treatment should be carried out according to the temperature, addition sequence, and stirring conditions recommended in the product TDS/SDS, while avoiding local overheating. Excessively high temperatures or local overheating may affect the color, odor, pH, or active ingredient stability of the raw material.

6. Anti-Freeze AES Addresses Low-Temperature Flowability

Anti-freeze AES refers to low-temperature-flow AES that has been optimized through formulation composition or production process and still maintains relatively good flowability under specified low-temperature conditions. Its main purpose is to improve pourability, pumpability, unloading efficiency, dilution efficiency, and freeze–thaw recovery at low temperatures. It does not mean that the product will remain completely unchanged in viscosity or will never solidify under all low-temperature conditions.

When selecting anti-freeze AES, the following points should be confirmed: ① whether it can be easily unloaded after low-temperature transportation; ② whether it can still be pumped after low-temperature storage; ③ whether it disperses easily during dilution; ④ whether it returns to a uniform state after freeze–thaw; and ⑤ whether it affects the viscosity, foam, transparency, and odor of the original formulation.

If a factory is located in an area with low winter temperatures, and standard AES has already shown obvious lumping, pumping difficulty, drum-bottom residue, or low dilution efficiency, the value of using anti-freeze AES will be more apparent.

Anti-freeze AES is not a unified standard name. Different manufacturers may use different approaches to improve low-temperature performance. Its low-temperature flowability may result from the combined adjustment of active matter content, water content, inorganic salts, impurity composition such as unsulfated matter, solubilizing systems, and production processes. Common influencing directions include:

Adjustment Direction	Possible Effect
Controlling the ratio of active matter to water	Reduces low-temperature viscosity and improves flowability
Reducing inorganic salt load	Reduces the risk of low-temperature crystallization and abnormal thickening
Controlling unsulfated matter	Reduces precipitation, turbidity, and odor risks
Introducing a suitable solubilizing system	Improves pourability and pumpability
Optimizing the production process	Improves batch stability and low-temperature consistency

7. How to Choose Between Standard Grade and Anti-Freeze Grade

7.1 Situations Where Standard AES Can Continue to Be Used

For factories with stable storage, transportation, and charging conditions, standard 70% AES still offers mature, stable, and economical advantages. Standard AES is suitable for the following situations:

Use Condition	Basis for Judgment
The factory is located in an area with relatively high winter temperatures	Low risk of raw material solidification at low temperatures
The warehouse has heat-insulation conditions	Raw material state is controllable
Mild preheating can be carried out before charging	Short-term viscosity increase can be addressed
Manual charging is the main method	Pumpability requirements are not high
The original formulation is already stable	Raw material substitution variables are not desired
Cost sensitivity is high	The standard grade is usually more cost-effective

7.2 Situations Where Anti-Freeze AES Is Suitable

Anti-freeze AES is more suitable for scenarios with higher low-temperature operation risks and higher production rhythm requirements. Priority should be given to anti-freeze AES in the following situations:

Use Condition	Value of Anti-Freeze AES
Winter production in northern or low-temperature regions	Reduces the risk of low-temperature thickening, crystallization, and unloading difficulty
Difficulty unloading from drums, IBCs, or storage tanks	Improves unloading efficiency and reduces residue
Automated charging system	Improves pumping stability
Standard AES has previously shown lumping or crystallization	Reduces winter operation risk
Dilution time affects production capacity	Improves dispersion and dilution efficiency
High requirements for winter batch stability	Reduces production fluctuations caused by low temperatures

A reasonable way to choose between standard grade and anti-freeze grade is to compare the total cost, including unloading time, charging loss, heating energy consumption, manual handling cost, shutdown risk, and formulation validation cost. If standard AES frequently causes production waiting time, drum-bottom residue, rework, or batch fluctuations in winter, anti-freeze AES may reduce the overall production cost even if its unit price is slightly higher.

The difference between standard AES and anti-freeze AES lies in low-temperature flowability and production suitability. Standard AES is more suitable for production scenarios with stable storage and transportation conditions, higher cost sensitivity, and mature formulations. Anti-freeze AES is more suitable for production scenarios involving low winter temperatures, high pumpability requirements, unloading difficulties, or dilution efficiency that affects production capacity.

8. Representative Chemical Classification Tables for Standard AES and Anti-Freeze AES Selection, Blending Applications, and Formulation Validation

Table 1. Primary Surfactants, Co-Surfactants, and Structure-Related Products

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Core AES primary surfactant	68585-34-2	S304383	Sodium lauryl polyoxyethylene ether sulfate	70%	Used for studies on cleansing, foaming, emulsification, salt thickening, and low-temperature flowability. It is a core reference product for selection and validation of standard and anti-freeze alcohol ether sulfate products.
Fatty alcohol structure-related raw material	112-53-8	D431501	1-Dodecanol	ACS, ≥98%	Used for studies related to the hydrophobic chain structure of alcohol ether sulfates. It can help in understanding the effects of carbon chain length on foam, wetting, emulsification, and low-temperature behavior.
Anionic reference surfactant	151-21-3	S432157	Sodium dodecyl sulfate (SDS)	Anhydrous, ACS, ≥99%	Used for comparative studies between non-ethoxylated sulfates and alcohol ether sulfates in terms of foam, detergency, micellar behavior, and irritation evaluation.
Anionic primary surfactant	68439-57-6	S304377	Sodium alpha-olefin sulfonate	≥92%	Used for studies on blended detergent systems with alcohol ether sulfates. It can be used to evaluate detergency, foam, low-temperature solubility, and the stability of household cleaning formulations.
Anionic household cleaning surfactant	25155-30-0	S592217	Sodium dodecylbenzenesulfonate (SDBS)	Anion Active Matter, 85%	Used for studies on blended systems of alcohol ether sulfates and alkylbenzene sulfonates. It can be used to evaluate detergency, foam, electrolyte response, and the performance of cost-oriented cleansing formulations.
Acid-form anionic surfactant raw material	27176-87-0	D432532	Dodecylbenzenesulfonic acid isopropanol solution (catalyst), solution	70 wt. % in isopropanol	Used for studies on alkylbenzene sulfonate detergent systems. When used as an acid-form raw material, neutralization conditions, pH, and solvent effects should be considered. It can be used as a reference against alcohol ether sulfate systems in terms of detergency, foaming, and electrolyte response.
Mild anionic surfactant	1847-58-1	S305259	Sodium lauryl sulfoacetate	≥97%	Used for studies on mild cleansing blends in alcohol ether sulfate systems. It can be used to evaluate foam richness, rinsing feel, and improvement in the irritation profile of cleansing systems.
Mild anionic surfactant	137-16-6	N432001	Sodium N-lauroyl sarcosinate	Suitable for synthesis	Used for mildness adjustment, fine-foam evaluation, and screening of blended cleansing systems based on alcohol ether sulfates.
Amino acid-based anionic surfactant	29923-31-7	S339866	Sodium lauroyl glutamate	≥95%	Used for mildness adjustment in alcohol ether sulfate systems, development of amino acid-based cleansing formulations, and evaluation of after-wash skin feel.
Amphoteric co-surfactant	61789-40-0	C665446	Cocamidopropyl betaine	Actives content 28%–32% in water	Used for studies on mildness, foam stability, and salt-thickening synergy in alcohol ether sulfate systems. It is a commonly used blending aid in shampoos, body washes, and hand soaps.
Amine oxide co-surfactant	1643-20-5	N755731	N,N-Dimethyldodecylamine N-oxide (DDAO)	BioReagent, ≥99%	Used for studies on foam boosting, foam stabilization, thickening synergy, and detergency performance in alcohol ether sulfate systems. Suitable for validation of dishwashing and household cleaning formulations.
Nonionic glycoside surfactant	58846-77-8	D112862	Decyl glucopyranoside	Biochemical reagent	Used for studies on nonionic blending in alcohol ether sulfate systems. It can be used to evaluate changes in foam, mildness, transparency, and low-temperature stability.
Nonionic glycoside surfactant	110615-47-9	L196324	Lauryl glucoside	≥40%	Used for studies on nonionic blending in alcohol ether sulfate systems. It can be used to evaluate mildness, foam, cleansing power, and the stability of transparent systems.
Nonionic foam-boosting and thickening aid	68603-42-9	C304384	N,N-Bis(2-hydroxyethyl)cocamide	Model: 6501 (1:1)	Used for studies on foam boosting, foam stabilization, and auxiliary thickening in alcohol ether sulfate systems. It can be used to evaluate foam stability, viscosity change, and appearance stability of detergent systems after blending.

Table 2. Products for Low-Temperature Flowability, Salt Thickening, and Rheology Modification

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Electrolyte thickener	7647-14-5	S433744	Sodium chloride	Anhydrous, high-purity, reagent grade, ≥99%	Used for salt-thickening curve testing in alcohol ether sulfate systems. It can be used to evaluate the onset of thickening, peak viscosity, viscosity drop caused by excessive salt, and viscosity recovery after low-temperature exposure.
Inorganic salt indicator and electrolyte	7757-82-6	S639099	Sodium sulfate	Anhydrous, PharmPure™, ChP	Used for studies on inorganic salt content, low-temperature crystallization, and system stability of alcohol ether sulfate raw materials. It can assist in evaluating differences between standard and low-temperature-flow products.
Hydrotrope	1300-72-7	S485589	Sodium xylene sulfonate solution	Mixture of isomers, 40 wt. % in H₂O	Used for solubilization, viscosity reduction, and transparency adjustment in high-surfactant-content systems. Suitable for studies on dilution, low-temperature flowability, and concentrated systems of alcohol ether sulfates.
Low-temperature flow and solubilizing agent	57-55-6	P432968	1,2-Propanediol	Basic-grade reagent, for preparation	Used for solubilization, low-temperature flowability, and freeze–thaw stability studies in cleansing systems. It can be used to evaluate the dilution and storage performance of anti-freeze alcohol ether sulfate systems.
Low-temperature flow and humectant aid	56-81-5	G755728	Glycerol	Anhydrous, UltraBio™, molecular biology grade, ≥99.5% (GC)	Used for humectancy, solubilization, and low-temperature stability studies in cleansing systems. It can be used to evaluate the effects of aqueous-phase composition on the flowability and skin feel of alcohol ether sulfate systems.
Rheology and dispersion modifier	9003-01-4	P661414	Poly(acrylic acid) (PAA)	Viscosity ≤2000 cP (25°C)	Used for studies on rheology, dispersion, and suspension performance in cleansing formulations. It can be used to evaluate the effects of electrolytes and surfactants on system viscosity and stability.
Cellulose rheology modifier	9004-62-0	H434475	2-Hydroxyethyl cellulose (HEC)	Average Mw ~380,000	Used for auxiliary thickening, suspension stability, and thixotropic performance studies in alcohol ether sulfate systems. Suitable for formulation validation of body washes, hand soaps, and cleansing gels.
Polysaccharide rheology modifier	11138-66-2	G104873	Xanthan gum	PharmPure™, USP	Used for suspension, thickening, and low-shear viscosity adjustment in cleansing systems. It can be used to evaluate the rheological stability of blended alcohol ether sulfate systems.

Table 3. Products for pH Adjustment, Chelation Stabilization, and Quality Control

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
pH adjuster	77-92-9	C434176	Citric acid	Anhydrous, PharmPure™, USP, JP, BP, European Pharmacopoeia (Ph. Eur.), fine-granular	Used for pH adjustment and stability studies in alcohol ether sulfate systems. It can be combined with citrate salts to establish a buffer system and evaluate the skin feel of finished products.
Buffer salt	6132-04-3	S434901	Sodium citrate dihydrate	Pharmaceutical grade, PharmPure™	Used for buffering adjustment in alcohol ether sulfate cleansing systems. It can be used to evaluate the effects of pH on foam, viscosity, transparency, and preservative-system stability.
Chelating stabilizer	6381-92-6	E433190	Ethylenediaminetetraacetic acid disodium salt dihydrate	UltraBio™, ultrapure grade, ≥98.5%	Used for metal ion control in alcohol ether sulfate cleansing systems. It can improve transparency, odor stability, preservative-system performance, and storage stability.
Impurity and quality-control related	123-91-1	D431640	1,4-Dioxane	Anhydrous, ≥99.8%	Used for impurity control, method development, and analytical reference studies related to alcohol ether sulfate raw materials. Suitable for raw material quality evaluation.

Note: The products listed above are representative Aladdin products for scientific research and formulation studies. For additional product specifications, grades, and COA information, please search by “product name/CAS/Cat. No.” on the Aladdin website.

References

[1] Cosmetic Ingredient Review Expert Panel. Safety Assessment of Sodium Laureth Sulfate and Related Salts of Sulfated Ethoxylated Alcohols as Used in Cosmetics. International Journal of Toxicology, 2010, 29(Suppl. 3): 151S–161S.

[2] National Center for Biotechnology Information. PubChem Compound Summary: Sodium Laureth Sulfate.

[3] Raghavan S. R., Kaler E. W., et al. Studies on surfactant micelles, salt thickening behavior, and the salt curve in shampoo-type surfactant systems.

[4] BASF. Texapon® N 70 / Texapon® N 70 NA Technical Information, Sodium Laureth Sulfate Technical Data Sheet.

[5] Rosen M. J., Kunjappu J. T. Surfactants and Interfacial Phenomena. Wiley.

[6] Myers D. Surfactant Science and Technology. Wiley.

[7] Tadros T. F. Applied Surfactants: Principles and Applications. Wiley-VCH.

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