The washing property of surfactants is their fundamental characteristic with the most practical applications. It is closely related to the daily life of thousands of households and is being increasingly applied in various industries and all kinds of industrial production.
Surfactants are the main active ingredients of detergents. Synthetic detergents would not exist without surfactants. Among all types of SAA, anionic surfactants were the earliest to be used and remain the most widely applied category, currently accounting for more than 50% of the total market demand. Anionic surfactants will continue to hold a dominant position for a period of time in the future.
I. Anionic Surfactants
The main types of anionic surfactants used as detergents include fatty acid salts (soaps), alkylbenzene sulfonates (ABS), fatty alcohol sulfates (AS), fatty alcohol polyoxyethylene ether sulfates (AES), alpha-olefin sulfonates (AOS), fatty alcohol polyoxyethylene ether carboxylates (AEC), and fatty acid methyl ester sulfonates (MES).
1. Soap
The surface-active part of soap molecules carries a negative charge, among which sodium and potassium salts of long-chain fatty acids account for approximately 25%. As the most widely used type of soap, it features abundant raw materials, convenient preparation and low cost. Industrially, it is generally produced by saponifying raw materials such as beef tallow and mutton fat with strong alkali, followed by salting out and separation of glycerol. Its biggest disadvantage is that when encountering divalent and trivalent metal ions such as Ca²⁺, Mg²⁺ and Fe²⁺ in aqueous solution, it will form calcium soap or magnesium soap with extremely low solubility, thus losing the inherent detergency of soap.
2. Alkylbenzene Sulfonates (ABS)
Sodium alkylbenzene sulfonate (R-C₆H₆-SO₃Na) is an important anionic surfactant. It has good solubility in water and is almost completely ionized. Its calcium and magnesium salts are highly soluble in water, endowing it with excellent hard water resistance. Among alkylbenzene sulfonates, linear alkylbenzene sulfonate (LAS) is low-priced, powerful in detergency, readily biodegradable and environmentally friendly. Therefore, up to now, no other surfactant used as detergent active ingredient can rival LAS in technical performance and economic benefits, making it hailed as the mainstay of the synthetic detergent industry worldwide. It is mainly applied in industrial and household detergents. Representative products include sodium dodecylbenzene sulfonate with excellent washing effect, and sodium octadecylbenzene sulfonate which boasts the strongest detergency in the sodium alkylbenzene sulfonate series.
3. Alpha-Olefin Sulfonates (AOS)
AOS is a high-performance detergent active ingredient. It is mainly used in hand sanitizers, shampoos, bubble baths, dishwashing detergents, industrial cleaning agents and laundry detergents.
4. Fatty Acid Methyl Ester Sulfonates (MES)
In its molecular structure, R represents an alkyl group and R’ represents a methyl group. For detergency performance, R with C16 and C18 carbon chains works best, while R with C14 carbon chain delivers the optimal hard water resistance. MES is a surfactant derived from natural oils and fats, possessing excellent washing performance and strong calcium soap dispersing power. It has outstanding compatibility with zeolite and is suitable for the production of phosphorus-free laundry detergents. Its calcium soap dispersing power is much higher than that of LAS, which is conducive to the production and application of compound soap and soap-based laundry detergents.
5. Fatty Alcohol Sulfates (AS) and Fatty Alcohol Ether Sulfates (AES)
The general formula of AS is ROSO₃Na, and AS with R as C14~C16 carbon chains exhibits good detergency. The general formula of AES is RO(C₂H₄O)ₙSO₃Na, and AES with R as C14~C15 carbon chains and n=1–2 shows favorable washing performance. Both AS and AES feature good biodegradability, strong detergency and excellent foaming property, making them suitable for formulating high-foam detergents. They are applicable to easy-care detergents and wool detergents, and are widely used in bubble baths, hair shampoos, cosmetics, hand dishwashing detergents, vegetable detergents and household detergents.
Nonionic surfactants exhibit excellent detergency against oily soils and a strong ability to prevent redeposition on synthetic fibers. They possess high tolerance to hard water and high-concentration electrolytes. The most prominent advantage of polyoxyethylene nonionic surfactants lies in the adjustability of their hydrophobic and hydrophilic moieties. The number of EO units can be regulated to adapt to various substrates and achieve optimal detergency.
1. Polyoxyethylene Alkyl Alcohol Ether
General formula: RO(C₂H₄O)ₙH, where R = C₁₂~C₁₈ and n is adjustable. This type of compound features high washing activity, reflected in the following aspects: a low critical micelle concentration (cmc), which means high detergency can be maintained even at low concentrations, powerful washing capacity, and soil redeposition resistance when cleaning synthetic fibers. It also delivers favorable low-temperature washing performance. It appears as white to pale yellow paste at room temperature and is soluble in water, with emulsifying, cleaning and wetting properties. It is mainly applied in household and industrial detergents as well as metal cleaners.
2. Polyoxyethylene Alkyl Phenol Ether
In the formula, R is mainly octyl, nonyl and dodecyl, with adjustable n value. It is characterized by strong capability to remove oil stains and grease. Typical products include OP series, OPE series and SOPE series. They feature excellent acid and alkali resistance as well as hard water tolerance, and have functions of decontamination, wetting and emulsification, applicable to metal processing and industrial cleaning agents.
3. Alkyl Polyglycoside (APG)
Alkyl polyglycoside is hailed as a new world-class nonionic surfactant.
Advantages of APG:
High interfacial activity and extremely low surface tension;
No cloud point and excellent high-temperature stability;
Outstanding washing performance, strong foaming power, good wetting, emulsifying capacity and dispersion stability;
Superior to all existing types of surfactants in terms of non-toxicity, low skin irritation and biodegradability.
Therefore, it is widely favored by numerous industries including detergent, cosmetics, food processing and pharmaceutical industries. Thanks to its easy rinsing and residue-free characteristics, it is especially suitable for dishwashing detergents and bottle cleaners.
Main application scenarios of APG in detergents are as follows:
Bath and Hair Detergents: Products formulated with APG are mild and non-irritating to the skin with rich and fine foam, and can exert an antistatic effect during shampooing. Most products are liquid and can also be made into soap bars.
Dishwashing Detergents: APG-based dishwashing detergents have good foaming performance, are skin-friendly with comfortable hand feel after use, and are easy to rinse without leaving traces.
Laundry Detergents: APG applied in laundry detergents provides excellent detergency. It can clean various fabrics such as cotton, wool and polyester, effectively removing soil and oil stains. It also endows fabrics with softness, antistatic property and shrinkage resistance, and can be formulated into laundry detergents that maintain superior washing performance even in hard water.
Hard Surface Cleaning: Besides dishwashing, APG can be used for cleaning other hard surfaces. It can be used as an active ingredient to prepare detergents applicable under strong acid conditions, and can prevent ferrous metals from oxidation and acid corrosion.
III. Zwitterionic Surfactants
Their molecular structure carries both positive and negative charges. Due to their special molecular structure, they possess the following characteristics in application: low toxicity and low irritation to the skin and eyes; excellent biodegradability and compatibility; good wetting, detergency and foaming properties. They are classified into the following types when used as detergents.
N-Acyl Amino Acid Type
They are mainly used as base materials for shampoos and cleaning agents, and are resistant to weak acids and hard water. Examples include N-acyl polyamino (polypeptide) carboxylate and Remipon A (Detergent 613, sodium oleoylamino polypeptide carboxylate).
Remipon A is synthesized from the condensation of fatty acyl chloride and polyamino acids obtained by protein hydrolysis. It therefore features low irritation and low toxicity, making it suitable for cosmetic applications. Remipon A exhibits strong lime soap dispersing power, detergency and emulsifying power. It is used as a detergent and emulsifier in the textile industry, and is ideal for washing silk and wool due to its mild degreasing ability.
Zwitterionic betaine surfactants deliver excellent detergency for cotton fabrics and polyester/cotton blended fabrics, with hydroxysulfobetaines offering particularly superior performance during washing. A typical example is Lauryl Dimethyl Betaine.
It is a colorless or pale yellow transparent liquid. It behaves as a cationic surfactant in acidic media and as an anionic surfactant in alkaline media, and is readily biodegradable. It has outstanding foaming performance and can soften hair, making it suitable for formulating mild, hair-conditioning shampoos as well as infant shampoos. With good hard water resistance, it can be used to prepare hard water detergents and also serves as a bactericide.
Post time: May-07-2026