The washing property of surfactants is the fundamental characteristic that gives surfactants their greatest practical applications. It is involved in the daily life of thousands of households and is increasingly applied in all walks of life and various industrial production processes.
Antistatic Effect of Surfactants
Fibers, plastics and other products often generate static electricity due to friction, which impairs their application performance. For example, fiber fabrics with static charges frequently suffer drawbacks such as clinging to the body, static adhesion, and a tendency to absorb dust and get dirty. The adverse impacts of static electricity on plastic products are even more severe. Static-charged plastic products not only readily adsorb dust, which damages the transparency, surface cleanliness and appearance of the products, but also reduces their service performance and value.
To eliminate such static phenomena, the surfactant antistatic method is widely adopted at present. Such surfactants are known as antistatic agents.
Section 1 Static Phenomena and Their Causes
Although there are some discrepancies in the results of the electrification sequence of fibers obtained by different testers, fibers containing amide bonds such as wool, nylon and artificial wool tend to carry positive charges. The electrification status of common plastics is shown in Table 10‑2. The electrification sequence of common substances from positive to negative is listed below:
(+) Polyurethane – Hair – Nylon – Wool – Silk – Viscose fiber – Cotton – Hard rubber – Cellulose acetate fiber – Vinylon – Polypropylene – Polyester – Polyacrylonitrile – Polyvinyl chloride – Vinyl chloride-acrylonitrile copolymer – Polyethylene – Polytetrafluoroethylene (-).
The exact mechanism of static electricity generation is not fully understood, yet there is a consensus that static electricity arises from mobile charges generated between objects when different types of objects rub against each other. The type of charge an object carries is determined by the gain or loss of electrons. An object becomes positively charged when it loses electrons and negatively charged when it gains electrons.
Section 2 Antistatic Agents
There are two main methods to eliminate static electricity:
(1) Physical methods. Since the magnitude of static electricity is affected by temperature and humidity, physical approaches such as adjusting temperature and humidity and corona discharge can be used to remove static electricity on the surface of articles.
(2) Surface chemical methods, namely using surfactants (also called antistatic agents) to conduct surface treatment on fiber and plastic products or blend them into plastics to achieve the purpose of static elimination.
1. Antistatic Agents for Fibers
Required properties of antistatic agents:
(1) Do not alter the hand feel of fibers; (2) Good antistatic performance with low dosage and effectiveness at low temperatures; (3) Good compatibility with resin fibers; (4) Excellent compatibility with other auxiliaries; (5) No foaming and no water stain formation; (6) Non-toxic and non-irritating to skin; (7) Maintain good stability.
Types of antistatic agents
The main types of antistatic agents used for fibers are cationic and amphoteric surfactants.
Mechanism of action of antistatic agents
The antistatic mechanism of surfactants used for fiber antistatic purposes is mainly reflected in two aspects: preventing static generation when fiber fabrics are subjected to friction and facilitating the dissipation of surface charges. The prevention of frictional electrification is closely related to the structure of surfactants, while the dissipation of surface charges is associated with the adsorption capacity and hygroscopicity of surfactants on fiber fabrics.
Cationic surfactants can easily adsorb onto negatively charged fiber surfaces via their own positive charges.
① They can neutralize the surface charges of fibers;
② Cationic surfactants adsorb on fiber surfaces in an orientation where positively charged quaternary ammonium ions attach to the fiber surface and hydrophobic hydrocarbon chains point outwards, forming an oriented adsorption film composed of hydrocarbon chains on the fiber surface. This adsorption film can effectively reduce friction on the fiber surface during friction and weaken frictional electrification.
For synthetic fibers with low polarity and strong hydrophobicity, cationic surfactants adsorb on fiber surfaces through van der Waals forces by their hydrophobic hydrocarbon chains, while polar quaternary ammonium groups face outward. The fiber surface is thus covered with hydrophilic polar groups, which not only improves the conductivity of the fiber surface but also increases its surface humidity, facilitating the dissipation of static electricity generated by friction and delivering antistatic effects.
The adsorption capacity of dioctadecyl ammonium chloride on natural fiber surfaces is significantly higher than that on synthetic fibers, indicating that it achieves better antistatic performance on natural fibers.
Like cationic surfactants, amphoteric surfactants carry positive charges and can adsorb on negatively charged fiber surfaces to neutralize static charges. Their hydrophobic groups also reduce friction. Compared with cationic surfactants, amphoteric surfactants have an additional anionic group in their molecular structure, which enables better moisture retention and charge dissipation. Therefore, amphoteric surfactants are high-performance antistatic agents, albeit at a relatively high price.
Anionic and nonionic surfactants show poor antistatic performance due to their low adsorption capacity on fiber surfaces. The adsorption amount of nonionic surfactants is not affected by the surface charge of fibers and is higher than that of anionic surfactants, yet they have weak effects on static dissipation. Hence their antistatic capacity is far inferior to that of cationic and amphoteric surfactants.
2. Antistatic Agents for Plastics
The antistatic mechanism of surfactants used as plastic antistatic agents is as follows: surfactants adsorb on plastic surfaces by their hydrophobic hydrocarbon chains through van der Waals forces, with polar groups extending outward. An oriented adsorption film of surfactants forms on the plastic surface to provide conductivity, allowing static charges to dissipate efficiently. Meanwhile, the adsorption film can also mitigate friction on plastic surfaces.
Classification of plastic antistatic agents by surfactant type:
(1) Anionic type;
(2) Cationic type;
(3) Amphoteric type;
(4) Nonionic type.
Antistatic agents can be divided into two categories by application method:
(1) Surface-coating antistatic agents;
(2) Compounding antistatic agents.
Post time: Oct-10-2026