The detergency of surfactants is their fundamental property with the most extensive practical applications. It is closely related to the daily lives of countless households and is also being increasingly adopted across all walks of life and various industrial production sectors.
Surfactants serve as the primary active ingredients in detergents; synthetic detergents would not exist without surfactants. Among all categories of surfactants (SAA), anionic surfactants were the first to be utilized by humans and remain the most widely used type, currently accounting for over 50% of total market demand.
I. Anionic Surfactants
The main types of anionic surfactants used in detergents include fatty acid salts (soaps), alkylbenzene sulfonates (ABS), fatty alcohol sulfates (AS), fatty alcohol polyoxyethylene ether sulfates (AES), α-olefin sulfonates (AOS), fatty alcohol polyoxyethylene ether carboxylates (AEC), and fatty acid methyl ester sulfonates (MES).
1. Soap
The surface-active portion of soap molecules carries a negative charge, with sodium and potassium salts of long-chain fatty acids accounting for approximately 25%. This widely used soap boasts the advantages of abundant raw materials, simple preparation and low cost. Industrially, it is generally produced by saponifying fats such as beef tallow and mutton fat with strong alkalis, followed by salting out to separate glycerol. Its biggest drawback is that when exposed to divalent and trivalent metal ions including Ca2+, Mg2+ and Fe2+ in aqueous solutions, it forms poorly soluble calcium soap or magnesium soap, which eliminates the detergency of soap.
2. Alkylbenzene Sulfonates (ABS)
Sodium alkylbenzene sulfonate (R-C6H6-SONa) is a vital anionic surfactant. It features good water solubility and almost complete ionization. Its calcium and magnesium salts have relatively high water solubility, granting it excellent hard water resistance. Among alkylbenzene sulfonates, linear alkylbenzene sulfonate (LAS) stands out for its low cost, powerful detergency, easy biodegradability and environmental friendliness. To date, no other surfactant used as detergent active ingredients can rival LAS in technical performance and economic benefits, earning it the reputation as the backbone of the global synthetic detergent industry. It is mainly applied in industrial and household detergents. Representative products include sodium dodecyl benzene sulfonate with outstanding washing performance, and sodium octadecyl benzene sulfonate, which delivers the strongest detergency within the sodium alkylbenzene sulfonate series.
3. α-Olefin Sulfonates (AOS)
AOS is a high-performance detergent active substance, widely used in hand sanitizers, shampoos, bubble baths, dishwashing detergents, industrial cleaners and laundry powders.
4. Fatty Acid Methyl Ester Sulfonates (MES)
In its molecular structure, R refers to alkyl groups and R’ represents methyl groups. For detergency, alkyl chains of C16 and C18 are optimal, while C14 alkyl chains offer the best hard water resistance. Derived from natural oils and fats, MES is a surfactant with remarkable washing capacity and strong calcium soap dispersing power. It exhibits excellent compatibility with zeolites, making it ideal for phosphate-free laundry powder manufacturing. Its calcium soap dispersing capacity far exceeds that of LAS, facilitating the production and application of compound soap and soap-based laundry powders.
5. Fatty Alcohol Sulfates (AS) and Fatty Alcohol Ether Sulfates (AES)
AS follows the general formula ROSO₃Na; chains with R = C14~C16 deliver favorable detergency. AES has the general formula RO(C2H4O)nSO₃Na, with R = C14~C15 and n = 1–2 providing optimal washing performance. Both AS and AES feature excellent biodegradability, strong detergency and superior foaming ability, making them suitable for high-foam detergent formulations. They are applicable to mild-care or wool detergents, and are extensively utilized in bubble baths, hair shampoos, cosmetics, hand dishwashing liquids, vegetable cleaners and household detergents.
Nonionic surfactants exhibit excellent detergency against oily soils and strong anti-redeposition performance for synthetic fibers. They also possess outstanding resistance to hard water and high-concentration electrolytes. The most prominent advantage of polyoxyethylene nonionic surfactants lies in the adjustable structure of their hydrophobic and hydrophilic moieties. By modifying the ethylene oxide (EO) unit count, they can be tailored for various substrates to deliver optimal detergency.
1. Polyoxyethylene Alkyl Alcohol Ethers
General formula: RO(C2H4O)nH, where R represents alkyl groups ranging from C12 to C18 and n is adjustable. These compounds feature superior washing activity reflected in the following aspects: a low critical micelle concentration (cmc), which enables strong detergency even at low concentrations, powerful cleaning capacity, and anti-soil redeposition properties when laundering synthetic fibers. Additionally, they deliver favorable low-temperature washing performance. They appear as white to pale yellow pastes at ambient temperature, dissolve in water, and provide emulsifying, cleaning and wetting capabilities. They are widely applied in household detergents, industrial cleaners and metal degreasers.
2. Polyoxyethylene Alkylphenol Ethers
In their molecular formula, R mainly refers to octyl, nonyl and dodecyl groups, with an adjustable n value. They are distinguished by remarkable oil and grease removal capacity. Typical commercial products include OP series, OPE series and SOPE series. They boast strong acid and alkali resistance as well as hard water tolerance, with combined detergency, wetting and emulsifying functions for metal processing fluids and industrial cleaning agents.
3. Alkyl Polyglucosides (APG)
Alkyl polyglucosides are recognized as a new generation of world-class nonionic surfactants.
Advantages of APG:
High interfacial activity and extremely low surface tension;
No cloud point and stable performance at high temperatures;
Excellent detergency, abundant foaming power, superior wetting/emulsifying capacity and dispersion stability;
Non-toxicity, mild skin irritation and superior biodegradability compared with all existing surfactant categories (core strengths and characteristics).
For the above merits, APG has gained exceptional popularity across numerous sectors including detergent manufacturing, cosmetics, food processing and pharmaceutical production. Moreover, its easy-rinsing and streak-free properties make it particularly suitable for dishwashing liquids and bottle cleaners.
Main application scenarios of APG in detergent formulations are listed below:
Bath and hair care detergents: Formulations based on APG are mild and non-irritating to skin, generating rich, fine foam and delivering anti-static effects during shampooing. End products are mostly liquid and can also be processed into soap bars.
Dishwashing liquids: APG-based dishwashing liquids offer stable foaming performance, gentle skin compatibility, smooth hand feel after use, easy rinsing and zero residual marks.
Laundry detergents: APG delivers outstanding detergency in laundry formulations, suitable for cleaning all types of fabrics such as cotton, wool and polyester. It effectively removes mud and oil stains while imparting fabric softness, anti-static and anti-shrink properties. It can also be formulated into laundry detergents that maintain powerful cleaning efficiency in hard water.
Hard-surface cleaners: Beyond dish cleaning, APG can be formulated for cleaning other hard surfaces. As an active ingredient, it can be compounded into detergents for strongly acidic environments, where it additionally inhibits oxidation and acid corrosion of ferrous metals.
Their molecular structure carries both positive and negative electrical charges. Due to this unique structural feature, they demonstrate the following application characteristics: low toxicity, mild irritation to skin and eyes, excellent biodegradability and compatibility with other surfactants, as well as favorable wetting, cleaning and foaming performance. Major types applied in detergents are categorized as follows:
1. N-Acyl Amino Acid Surfactants
They serve as core raw materials for shampoos and cleaning agents, with resistance to weak acids and hard water. Representative examples include N-acyl oligopeptide carboxylates and Remipol A (613 detergent, sodium oleoyl peptide carboxylate).
Remipol A is synthesized via the condensation reaction between fatty acid chloride and oligopeptides derived from protein hydrolysis. It features low irritation and low toxicity, making it applicable in cosmetic formulations. It exhibits powerful lime soap dispersing capacity, detergency and emulsifying power. In the textile industry, it functions as a detergent and emulsifier; its weak degreasing performance renders it ideal for washing silk and wool fabrics.
2. Betaine-Type Amphoteric Surfactants
Betaine amphoteric surfactants deliver excellent detergency on cotton fabrics and polyester/cotton blended textiles, with hydroxy sulfobetaines showing particularly prominent advantages during laundering processes.
Take dodecyldimethyl betaine as an example: it exists as a colorless to pale yellow transparent liquid, behaving cationically in acidic media and anionically in alkaline media, and is readily biodegradable. It features outstanding foaming performance and softens hair, making it a primary raw material for mild conditioning shampoos and infant hair care products. Thanks to its strong hard water resistance, it is used to formulate hard-water-compatible detergents, and can also act as a bactericide.
Post time: Jul-02-2026