What are antistatic agents, and what are their mechanisms and types?

Antistatic agents are additives that can reduce the accumulation of static electricity during the processing and use of plastics and lower the surface resistivity of the material. It is well known that polymer materials generally have excellent electrical insulation properties, but static electricity is easily generated through friction. The static voltage can sometimes reach several thousand or even tens of thousands of volts. The resulting discharge phenomena can cause fires and even endanger life safety. Therefore, it is necessary to eliminate the static electricity on plastic products.

(1) Mechanisms of antistatic agents

The mechanisms by which antistatic agents used by plastic manufacturers reduce or eliminate static electricity on the surface of Plastic Products mainly fall into two categories:

1. Increasing conductivity: Since plastics have excellent electrical insulation, once static electricity is generated, it is difficult to eliminate. Increasing conductivity makes it harder for charge to accumulate. Therefore, many antistatic agents contain hydrophilic groups that increase the moisture absorption of the product surface, forming a conductive film that facilitates the dissipation of static electricity. Additionally, ionic antistatic agents can increase the ion concentration on the product surface, thereby enhancing conductivity. Increasing conductivity accelerates charge dissipation and is a relatively proactive antistatic method.

2. Reducing the amount of static electricity generated by friction: Static electricity arises from friction, produced when other materials rub against the product. The greater the friction, the more static electricity accumulates. To address this, the surface smoothness of the product can be increased to reduce the friction coefficient, thereby decreasing friction. Also, using antistatic agents with a high dielectric constant can increase the dielectric properties between rubbing materials, reducing the static charge produced by friction.

(2) Classification of antistatic agents

1. According to whether the hydrophilic groups in the antistatic agent molecules can ionize, antistatic agents are classified as ionic and nonionic types. Among the ionic types, there are anionic, cationic, and zwitterionic antistatic agents. Ionic antistatic agents are widely used because they can dissipate charge directly through their intrinsic ionic conductivity.

There are many types of anionic antistatic agents, mainly including sulfonates, acidic phosphate esters, and neutral phosphate esters. These are mainly used as oils and finishing agents on fibers and textiles. Common cationic antistatic agents include amine salts, quaternary ammonium salts, and alkyl imidazolines. They possess excellent antistatic properties and are the main types of antistatic agents. Zwitterionic antistatic agents can be used together with anionic and cationic agents and have excellent antistatic performance, with quaternary ammonium inner salts being a major variety.

Nonionic antistatic agents are less effective than ionic types but have good thermal stability and are less prone to aging. The main varieties include polyols, polyol esters, and epoxy ethylene adducts of alkyl amines.