Six Factors Affecting Antistatic Performance

Whether using external antistatic agents, or internal antistatic agents for antistatic treatment of materials, environmental relative humidity, temperature and surface concentration and other factors have a certain impact on the antistatic performance, this paper will be introduced in detail.

1. The influence of humidity and temperature

The antistatic effect of plastic treated with antistatic agent is related to its ambient temperature and humidity. The higher the humidity and the higher the temperature, the better the antistatic effect. In fact, at room temperature, the change of temperature has little influence on the antistatic effect, but the increase of temperature has a tendency to increase the antistatic performance, because the migration of antistatic agent molecules increases with the increase of temperature. The change of humidity has great influence on the antistatic effect. After surface treatment with antistatic agent, the leakage of polymer surface charge is not only electron conduction, but also the movement of ion charge. The charge movement is caused by the formation of hydrogen bonds between the hydrophilic groups of the antistatic agent. Because the antistatic agent has hygroscopic property, and can produce ionic groups after hygroscopic, the electrical conductivity of the plastic surface is greatly increased, promoting the play of the antistatic effect. Therefore, the higher the ambient humidity, the better the antistatic effect.

2. The influence of compatibility with resin

The use of surfactants as internal antistatic agents in plastics is mainly the use of this kind of surfactants through internal molecular migration, forming conductive films on the surface. If the compatibility of plastic and the selected antistatic agent is too good, the migration of antistatic agent molecules is difficult due to the force between the two molecules, the surface loss of antistatic agent can not be timely supplemented, difficult to play a good antistatic effect, must add too much antistatic agent, but the addition of too much, will affect the other properties of plastic. If the compatibility is very poor, it often causes processing difficulties. At the same time, a large number of antistatic agents will be precipitated, which not only affects the appearance quality of the products, but also the precipitated antistatic agents will soon be lost, and it is also difficult to maintain a lasting antistatic effect.

Therefore, choosing the appropriate combination of hydrophilic and oil-philic groups, and trying to find the suitable compatibility between antistatic agent and resin, is the first consideration of antistatic agent, especially the internal antistatic agent molecular design.

3. The effect of polymer molecular structure

Among the parameters related to molecular structure, the first light considers the glass transition temperature (Tg). The migration of antistatic agent to plastic surface is mainly through the molecular movement of polymer chain. The glass transition temperature of plastic directly affects the migration rate of antistatic agent molecules. Above the glass transition temperature, the polymer molecules show microbrownian motion, and the antistatic agent is added to the polymer molecules, which migrates to the surface by means of the chain movement of the molecules. Below the vitrification temperature, the polymer molecules are frozen, and the antistatic agent is almost closed between the polymer molecules, which is difficult to migrate to the surface.

4. The influence of the surface concentration of antistatic agent

The distribution of antistatic agent on the surface of plastic products must reach a certain concentration to show the antistatic effect, the concentration is called the critical concentration. The critical concentrations of various antistatic agents vary depending on their own chemical structure, composition, polarity, temperature, and use. For general polymer compounds is about 0.5 x 10-2 mg/cm2. Theoretically speaking, antistatic products only rely on the orientation of the hydrophilic group in the air formed by the single molecule conductive layer on the surface of the product, it will not have significant antistatic effect. Only when the antistatic agent molecule has more than 10 layers of thickness on the surface, it will produce excellent antistatic effect due to the orientation of the hydrophilic group. Of course, the concentration of antistatic agent on the surface is completely dependent on the rate of migration of antistatic agent molecules to the surface.

5. The influence of other additives

Polymer materials in processing, often add some stabilizer, pigment, plasticizer, lubricant, dispersant or flame retardant and other additives. The interaction between these additives and antistatic agents will also have a great influence on the antistatic effect. For example, the anionic stabilizer of metal soap and the antistatic agent can easily compound with each other, which not only reduces the antistatic performance, but also reduces the thermal stability. The lubricant usually migrates to the polymer surface quickly, which inhibits the migration of antistatic agent. This is like covering a layer of lubricating oil on the antistatic agent layer, reducing the surface concentration of antistatic agent, significantly affecting the antistatic effect; In contrast, there are certain lubricants that facilitate the migration of antistatic agents.

6. The impact of processing

The processing method of antistatic products is different, and the dispersion state and migration speed of antistatic agents are different, so the antistatic effect is different. If the polymer is not formed after melting, it is cooled immediately at room temperature lower than its glass transition temperature, antistatic agent is difficult to spread to the surface of the product, thus there is not enough antistatic effect. If the product is cooled at an environment higher than the glass transition temperature, the movement of large molecular chain segments helps the diffusion of the antistatic agent, so that not only the product can show enough antistatic effect, but also the use of friction or water to remove the antistatic agent on the surface, but also can quickly recover its antistatic effect.

In addition, appropriate treatment of the plastic surface, such as partial oxidation of the surface, can produce a polar group, it and antistatic agent interaction often have additive effect, so that the antistatic effect is fully played. For different resins, to achieve the same antistatic effect, the amount of antistatic agent added is different. Therefore, in the design and use of antistatic agents need to consider the above factors, through the experiment to screen the variety of antistatic agents and the best use.