The use of antistatic agents can be divided into two types: external coating method and internal blending method. The external coating method has the advantages of simple operation, low material consumption, low heat resistance requirements of the antistatic agent, and does not affect the molding and processing performance of the product. However, the antistatic effect cannot last. After washing or rubbing, the antistatic agent is coated The layer is easy to fall off, so it is a temporary anti-static treatment. The internal blending method has the advantages of washing resistance, friction resistance, heat resistance, long-lasting antistatic effect, and simple use method.
How to use antistatic agent
1) Cleaning In order to obtain a uniform and dense antistatic agent coating film, the plastic surface must be cleaned before applying the antistatic agent to completely remove surface dust, Grease etc. It can be cleaned with about 1% neutral detergent solution. After cleaning, it needs to be placed in a clean room to dry.
2) Liquid preparation Use water, ethanol or ethyl acetate and other solvents to prepare the antistatic agent into a solution with a concentration of 0.2%~2%. Under the premise of electrostatic effect, it should be as thin as possible, because the solution with high concentration will be sticky and easy to absorb dust.
3) Coating The coating method is selected according to the shape of the product. The commonly used coating methods include direct method, dipping method and spraying method. The direct method is to apply the antistatic agent liquid on the product with tools such as cotton cloth, flannel, brush and roller. It is simple and effective, and is the most widely used. The dipping method is to immerse the product in the antistatic agent solution, which is suitable for small products with complex shapes or large quantities. The spraying method is to spray the antistatic agent liquid on the product with a spray gun, which has the advantages of fast speed, high efficiency and uniform coating film.
4) Drying The coated product should be fully dried to harden the coating layer. , It takes about 3 hours to dry. After drying, it should be placed under natural environmental conditions for 5 hours.
Internal blending method operation requirements
The blending method is to mix the antistatic agent and resin mechanically and then process it to make antistatic products. Commonly used antistatic agents are cationic and zwitterionic.
Antistatic agents are hygroscopic compounds that contain a certain amount of water. In the molding process, the existence of a small amount of water will cause the quality of the product to decline, so the antistatic agent should be fully dried before being added to the resin. It can be dried for 4 hours under hot air at 70 ~ 80C.
The amount of antistatic agent added should be determined according to the performance of the antistatic agent itself, the type of resin, processing conditions, product shape and the degree of antistatic effect. The general adding amount is 0.3% ~3.0%. Thin products require less addition than thick products.
The mechanism of antistatic agent
Different types of antistatic agents not only have different chemical compositions and usage methods, but also have different mechanisms of action.
(1) Mechanism of external coating antistatic agent
This type of antistatic agent is generally used as a solvent or dispersant with water, alcohol or other organic solvents. When the polymer material is impregnated with an antistatic agent, the lipophilic group in the molecule of the antistatic agent will be adsorbed on the surface of the material. After impregnation and drying, on the surface of the polymer material after dehydration, the hydrophilic groups in the antistatic agent molecules are arranged toward the air side, which is easy to absorb environmental moisture, or combine with moisture in the air through hydrogen bonds to form a The monomolecular conductive layer makes the generated static charge leak quickly to achieve the purpose of antistatic.
(2) Mechanism of surfactant internally blended antistatic agent
And in the molding process of polymer materials, if there is a sufficient concentration of antistatic agent, when the mixture is in a molten state, the antistatic agent molecules will be in the resin and The interface between air or resin and metal (machinery or mold) forms the densest orientation arrangement, in which the lipophilic group extends to the inside of the resin, and the hydrophilic group extends to the outside of the resin. After the resin is cured, the hydrophilic groups on the antistatic agent molecules are arranged towards the air side, forming a monomolecular conductive layer.
During processing and use, stretching, rubbing and washing will cause damage to the antistatic agent molecular layer on the surface of the material, and the antistatic performance will also decrease. However, unlike the external coating antistatic agent, after a period of time, the antistatic agent molecules inside the material will continue to migrate to the surface, so that the defect can be restored and the antistatic effect can be displayed again.
Since starting withThe above two types of antistatic agents achieve the purpose of antistatic by absorbing environmental moisture and reducing the surface resistivity of the material, so they are more dependent on environmental humidity. Obviously, the higher the ambient humidity, the stronger the water absorption of the antistatic agent molecules, and the more significant the antistatic performance.
(3) Mechanism of polymer permanent antistatic agent
Permanent polymer antistatic agent is a new type of antistatic agent researched and developed in recent years, which belongs to hydrophilic polymer.
When it is blended with the polymer matrix, on the one hand, due to the strong mobility of its molecular chains, it is easy for protons to move between the molecules, and it conducts and Release the generated static charge;
On the other hand, the antistatic ability is reflected by its special dispersion form. That is, the polymer permanent antistatic agent is mainly distributed in fine layers or tendons on the surface of the product to form a conductive surface layer, and is almost spherical in the center to form a so-called “core-shell structure”. Via leaks static charge.
Because the polymer permanent antistatic agent achieves the antistatic effect by reducing the volume resistivity of the material, it does not completely rely on surface water absorption, so it is more affected by the humidity of the environment Small.
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