As the core cosmetic raw materials in the fields of daily chemicals, textiles, industrial cleaning, etc., surfactants, the two categories of anions and cations, with their different charge characteristics and molecular structure, form a clear distinction in performance and application scenarios.Among them, the cationic surfactants represented by
Cetrimonium chloride and the anionic surfactants represented by OSMFACT ® MY CASD (cetearyl alcohol & sodium lauryl sulfate) are classic products in their respective fields. The characteristics, laws of action and application directions of the two have become an important basis for formula design and raw material selection in the industry.
Cationic surfactant
The core feature of cationic surfactants is that after dissociation in an aqueous solution, the hydrophilic group carries a positive charge. The hydrophilic group is mostly a quaternary ammonium salt group, while the hydrophobic group is mainly a long-chain alkyl group. cetrimonium chloride is a typical representative of this category. With its unique positive charge characteristics, it has become the core raw material of
Skin Conditioning Agents and plays an irreplaceable role in the fields of care, textiles, disinfection, etc.
Judging from the interaction between molecular structure and electric charge, the positively charged hydrophilic groups of cationic surfactants are the core support of their properties. Such groups can easily electrostatic adsorb with various surfaces with negative charges, which is also the key reason for their softness, antistatic, sterilization, color fixing and other functions.Taking cetrimonium chloride as an example, its quaternary ammonium salt structure provides a stable positive charge center, and the long-chain cetyl group, as the hydrophobic part, can be firmly attached to the negative charge interface. When used in the textile field, its positive charge center can be closely combined with the negative charge group on the surface of the fiber, forming a layer of hydrophobic protective film on the surface of the fiber, greatly reducing the coefficient of friction between the fibers, allowing the fabric to obtain a soft and smooth feel, while effectively neutralizing static electricity on the surface of the fiber, and avoiding problems such as pilling and sticky dust in the processing and use of the fabric. It is the core component of
Cationic Softener.
In the field of washing and care, the adsorption properties of cationic surfactants are also outstanding. The surface of the hair will carry negative electricity due to daily friction and cleaning. cetrimonium chloride can be firmly attached to the surface of the hair through electrostatic adsorption, forming a thin and thin conditioning film, which can not only reduce the friction between the hair scales, make dry and frizzy hair smooth and easy to comb, but also lock in the moisture inside the hair and enhance the gloss of the hair. Therefore, it has become an important raw material for conditioning care products such as conditioners and hair masks.In addition, its positive electrical properties can also act on the cell membrane of bacteria, adsorb and destroy the negatively charged cell membrane structure of bacteria, making it inactive. This feature makes cationic surfactants widely used in disinfectants and antibacterial care products.
Judging from the structural stability and compatibility characteristics, the quaternary ammonium salt group of cationic surfactants has a stable structure and can maintain good surface activity in acid and neutral solutions, but there is a strong electrostatic interaction between it and anionic surfactants. When the two are directly combined, an insoluble ionic complex will quickly form, resulting in a complete loss of the surface activity of both parties. Therefore, in conventional formulation design, the two will not be directly mixed, which is an important compatibility principle for the application of cationic surfactants.However, its compatibility with nonionic surfactants is good, and the performance complementarity can be achieved after the combination of the two, further improving the stability and use effect of the product.
In terms of the subdivision of application fields, the core advantages of cationic surfactants are concentrated in the needs of “functional modification”. In addition to washing and conditioning, textile softness, it also plays an important role in printing and dyeing, water treatment, papermaking and other fields.
1. In the field of printing and dyeing, it can be used as a color fixing agent. By combining the positively charged group with the negatively charged group of the dye, the adsorption fastness of the dye on the fiber can be improved, and the phenomenon of fabric fading can be reduced.
2. In the field of water treatment, it can be used as a flocculant to adsorb negatively charged impurities and colloids in the water, condense and precipitate it, and realize water purification.
3. In the field of papermaking, it can be used as a gluing agent to improve the water resistance and physical strength of the paper.
The current research and development and application trend of cationic surfactants is developing towards high efficiency, environmental protection and multi-function.The industry continues to develop low-foaming, easily biodegradable quaternary ammonium salt products to reduce its burden on the environment.
Anionic surfactant
Anionic surfactants are the most widely used and most used surfactant category. Their core feature is that the hydrophilic groups in the aqueous solution carry a negative charge after dissociation. The hydrophilic groups are mainly sulfonate and carboxylate, and the hydrophobic groups are long-chain alkyl groups. MY CASD is a classic representative product of this category.The product is white to yellowish granular, with a conventional specification of 25kg/bag, corresponding to CAS No. 246159-33-1/151-21-3. It combines the strong interfacial activity of sodium lauryl sulfate with the emulsifying and thickening properties of cetearyl alcohol to become the core raw material for cleaning and emulsifying products. It is widely used in daily chemicals, industrial cleaning, oilfield mining and other fields.
Judging from the interaction between molecular structure and electric charge, the negatively charged hydrophilic genes of anionic surfactants can easily bind to the cations in the solution to form stable ion pairs. This interaction law directly determines its micelle formation, aggregation state and core properties.Quantum chemical studies have shown that the polar heads of sulfonate and carboxylate anionic surfactants will form a stable 2:1 ion pair with two oxygen atoms and a single cation.Before binding to the cation, the α-methylene group on the molecule has a significant negative charge and can be classified as part of the polar head. Under the induction of the cation's charge, the α-methylene group will turn into a weak positive charge, narrowing the scope of action of the polar head.At the same time, the hydrophobic tail chain of anionic surfactants will have a weak positive charge, so that the micelle core has a certain polarity, and this polarity is between the alkane oil phase and the aqueous phase. This characteristic enables it to stably form micelles in the aqueous phase system, which provides a structural basis for its emulsification, solubilization, and cleaning capabilities.
The stable formation of micelles allows anionic surfactants to have excellent surface activity and can quickly reduce the surface tension of water. When exposed to hydrophobic pollutants such as oil and dirt, the hydrophobic tail chain will be inserted into the pollutant, while the hydrophilic base remains in the aqueous phase. Through stirring, rubbing and other external forces, the pollutants are wrapped into micelles and dispersed in the water to achieve a cleaning effect.MY CASD uses this principle. The sulfonate group of sodium lauryl sulfate dissociates to bring strong cleaning power and foaming properties, which can quickly peel off oil stains on the surface of the object, while cetearyl alcohol optimizes the product's emulsifying properties and foam stability. At the same time, it reduces the irritation of sodium lauryl sulfate, allowing the product to be cleaned while taking into account the use experience.
In terms of performance, the core advantages of anionic surfactants are concentrated in the three aspects of cleaning, foaming and emulsification, and they have good temperature resistance and alkali resistance, and can still maintain stable surface activity in alkaline and medium and high temperature systems. This feature allows it to show its strength in the industrial field.
1. In the field of daily chemicals, it is the core raw material of cleaning products such as shampoo, shower gel, cleanser, dishwashing detergent, laundry detergent, etc., relying on strong foaming and cleaning power to meet daily cleaning needs.
2. In the field of industrial cleaning, it can be used in metal cleaning, equipment degreasing and other scenarios to effectively remove stubborn oil stains in industrial production.
3. In the field of oilfield extraction, sulfonate anionic surfactants can effectively reduce the interfacial tension of oil and water, improve the recovery rate of crude oil, and become an important additive for tertiary oil recovery.
Judging from the compatibility and application characteristics, the compatibility of anionic surfactants is relatively flexible, and they can be freely combined with nonionic surfactants. After the combination of the two, the emulsifying and solubilizing capabilities of the product can be further improved, and the foam stability and gentleness can be improved. This is also a common collocation method in daily chemical formulas.
The current research and development direction of anionic surfactants mainly revolves around “improving gentleness, reducing irritation, and optimizing performance”.Traditional anionic surfactants such as pure sodium lauryl sulfate, although they have strong cleansing power, are relatively irritating. In the industry, they are combined with cetearyl alcohol, polyols and other substances, or develop new products such as alcohol ether sulfonates and fatty acid methyl ester sulfonates to maintain cleanliness while greatly improving gentleness and adapting to the care needs of special groups such as sensitive skin and infants.
Summary
Although cationic and anionic surfactants are the same as the core categories of surfactants, due to the essential differences in charge characteristics, they have formed very different performance systems and application directions.Cationic surfactants take positive charge as the core, mainly focus on interfacial adsorption and functional modification, and perform well in conditioning, softening, sterilization, and color fixing.Anionic surfactants are based on negative electricity, relying on stable micelle formation capabilities, focusing on core functions such as cleaning, emulsification, and foaming, and becoming the main force of cleaning products in various fields.
The interaction law and compatibility principle of the two provide an important basis for the formulation design of the industry, and through the bridging effect of nonionic surfactants or the phased use, the complementary properties of the two can be realized to meet diversified application needs.At the same time, the in-depth study of the charge interaction and molecular structure of the two also provides theoretical support for the research and development of new types of zwitterionic surfactants.
Hubei Mingya New Material Technology Co., Ltd.
