Know About Anti-static ESD Plastic

Plastic products are widely used in various fields such as household appliances, transportation, electronics and electrics because of their excellent insulating properties. However, this high insulating properties and often make it in the application, due to friction peeling and generate, accumulation of electric charge, to the production and application of many hidden dangers.

The materials can be categorized according to the surface resistivity:

Insulating materials: 10^12~10^15 ohm/sq

Antistatic Material: 10^10~10^12 ohm/sq

Static dissipative materials: 10^6~10^12 ohm/sq

Conductive materials: ≤ 10^5 ohm/sq

How to eliminate static electricity accumulated on the surface of plastic products as well as to prevent its surface from generating static electricity has been a popular direction in the field of polymer materials research.

The amount of static electricity generated by plastics can be expressed in terms of their surface resistivity or volume resistivity. Different types of plastic products often show different surface resistivity and volume resistivity. Generally speaking, the larger the surface resistivity or volume resistivity, the easier it is for plastic products to accumulate electricity, and the more significant the electrostatic hazard.

The order of charge is:

(positively charged) polyurethane, nylon, acetate, Polypropylene, polyester, polyacrylonitrile, polyvinyl chloride, vinyl chloride-acrylonitrile copolymer, Polyethylene, Polytetrafluoroethylene (negatively charged).

Electrostatic hazards

(1) Electrocution

In general, static electricity does not cause direct harm to the person, but electrocution can occur, because very little static charge, it is enough to form a very high static voltage.

For example, in the production of motion picture film, the static voltage generated can sometimes be as high as several thousand volts, making it easy for people to be electrocuted. Generally produce electrocution static voltage of 8000V.

(2) Discharge

When the static voltage is greater than 500V, a spark discharge can occur, if there are flammable substances in the environment at this time, it often leads to major fires and explosions, such as some mine explosions and fires, is due to the plastic products produced by electrostatic sparks.

(3) electrostatic attraction and repulsion and the problems arising from the role of the electrostatic force

For example, in the manufacturing process of plastic film, due to electrostatic attraction, making the film adheres to the machinery, not easy to detach. Another example, due to electrostatic attraction, plastic products will adsorb dust in the air, affecting the beauty of the products; film production process due to static electricity and affect the clarity of the film and the sound quality of the record and so on.

Anti-static methods

(1) Use conductive devices to eliminate static electricity during the processing of plastic products.

(2) Increase the air humidity in the environment of processing and use of plastic products, which is conducive to inhibit the generation of static charge and promote the leakage of charge.

(3) The use of blending with structural conductive polymer materials or through graft copolymerization to change the structure of the polymer, so that it carries a greater number of polar groups or ionized groups, reducing the resistivity and increasing the electrical conductivity.

(4) The use of strong oxidizing agent oxidation or corona discharge treatment of the surface of plastic products to improve the surface conductivity of the material.

(5) Apply conductive coating on the surface of the product or composite layer of conductive film.

(6) Add conductive fillers in plastics, such as graphite, carbon black, metal or metal oxide powder, etc., through the mixing of conductive fillers dispersed into the plastic, so that it becomes a composite conductive plastic.

(7) Add antistatic agent, antistatic treatment of the material, so that its surface activation, improve the surface conductivity of the material.

Antistatic Application

Static elimination requires volume resistivity of less than 10^12 Ω-cm or less, but in fact most plastics (except PF, PVA) volume resistivity can not meet the requirements of the elimination of static electricity, they have to be antistatic treatment.

Electromagnetic shielding requirements volume resistivity in 10 ~ 10 ^ 4 Ω - cm. electromagnetic wave interference is essentially noise interference, measured in decibels (dB). Shielding effect is good or bad, can be divided into the following grades: low shielding 10 ~ 30dB; shielding 30 ~ 60dB; good shielding 60 ~ 90dB; high shielding > 90dB. For example, electronic equipment requires shielding up to 35dB or more.

The conductor of electricity requires volume resistivity below 10 Ω-cm.

Antistatic Materials

Whether a plastic product will carry static electricity or the magnitude of static electricity can be evaluated by volume resistivity or electrical conductivity.

Insulator: Volume resistivity >10^12 Ω-cm or conductivity <10^-9S/cm.

Semiconductor: volume resistivity 10^6 to 10^12 Ω-cm or conductivity 2 to 10^-9S/cm.

Conductor: volume resistivity <10^6Ω-cm, or conductivity >2S/cm.

Good conductor: volume resistivity <10Ω-cm

Antistatic plastics require their volume resistivity to fall below 10^12 Ω-cm;

Conductive plastics require their volume resistivity to be less than 10^6 Ω-cm or conductivity >2S/cm.

Anti-static plastics are usually divided into the following types:

1. Conductive plastics: These plastics are usually mixed with conductive agents, such as carbon black or metal powder, during the manufacturing process to increase the conductivity of the plastic. These plastics usually have a high electrical conductivity, which can effectively eliminate or minimize the buildup of static electricity. Common conductive plastics include polypropylene, polyethylene, and Polystyrene

2. Antistatic plastics: these plastics are usually surface after special treatment, so that it has a certain degree of conductivity, thereby reducing the generation or accumulation of static electricity. This treatment includes the surface of the conductive coating, add antistatic agent. Antistatic plastics are commonly used in the need to prevent electrostatic interference but do not require a high degree of conductivity of the occasion, such as electronic product shells, medical equipment and so on.

3. Electrostatic shielding plastic: this type of plastic has a special shielding structure or added shielding materials, can effectively block or reduce the interference of external electromagnetic fields on the internal equipment, but also to reduce the generation or conduction of static electricity. Static shielding plastics are commonly used in electronic products such as shells, electromagnetic shielding cover and other components.

4. Static dissipative plastics: these plastics have the ability to quickly release static electricity to the surrounding environment, thereby reducing the accumulation of static electricity. Static dissipative plastics are usually surface after special treatment or added to be able to quickly release the charge of the compound, such as oxides. They are commonly used in applications that require rapid release of static electricity, such as semiconductor manufacturing equipment and dust explosion hazardous areas.

Anti-static grade

Conductive:

Conductive type antistatic materials typically have very low resistance values, typically below 10 to the 6th power ohm. This means they are able to discharge charges quickly, especially when grounded or connected to a low potential point.

Conductive-type materials are widely used in many high-precision environments, such as wafer production lines, operating rooms, and armories. In these locations, the buildup of static electricity can lead to serious problems such as incorrect instrument readings, miscalculations, and even sparks that cause more serious accidents.

Static Dissipative:

Static dissipative antistatic materials typically have a resistance value between the 6th power of 10 and the 9th power of 10 ohms. These materials dissipate charge slowly, with longer discharge times and lower discharge currents than conductive types.

Static dissipative materials are widely used in areas such as the manufacture of electronic components to ensure that rapid buildup of charge does not occur when electronic components come into contact with storage containers, thereby improving product safety and reliability.

Antistatic type:

Antistatic-type antistatic materials typically have resistance values between the 9th power of 10 and the 11th power of 10 ohms. Despite their higher resistance values relative to conductive and static dissipative types, they still provide excellent antistatic properties.

These materials are suitable for products that are very sensitive to static electricity, such as high-precision instruments and certain electronic components.