Static Electricity in Plastics and Its Prevention
Plastics are all polymer materials with surface and volume resistivity greater than 10^12. This gives plastics excellent insulating properties. However, for the same reason, they are highly susceptible to static electricity generation. Plastics and their products are frequently exposed to electromagnetic induction during production, handling, contact, separation, friction, and collisions. This creates factors that contribute to static electricity generation. How to effectively prevent static electricity generation has been a topic of concern and expectation for many years.
The concept of antistatic properties in plastics: When the surface resistivity of plastics and their products is greater than 10^12, static electricity is easily generated; between 8 and 10^12, they have certain antistatic properties; between 6 and 8^12, they have good antistatic properties; between 4 and 6^12, they have optimal antistatic properties; and below 4^12, they exhibit considerable conductivity, classifying them as conductors or semiconductor materials.
Prevention and Control of Static Electricity in Plastics:
1. Adding hygroscopic materials that are harmless to plastics (auxiliaries) reduces their surface resistance. This is called an antistatic agent for plastics. The type of antistatic agent used depends on the type of plastic. Both ionic and non-ionic antistatic agents are hygroscopic; after adding these additives, the materials absorb moisture from the air, reducing surface resistance and achieving antistatic properties.
2. Directly using conductive plastics to process products is the origin of conductive plastics (resins). Currently, most conductive plastics in the domestic market are still black additive-based conductive plastics; light-colored conductive plastics are still under development.
Selection of Conductive Plastics:
1. Antistatic agents are categorized by plastic type, including PVC, PP, PE, ABS, HIPS, etc., with prices ranging from tens of yuan/kg. The addition amount is 1-3%. After addition, the surface resistance is generally between 10⁸ and 10¹⁰, especially in areas with high humidity, where the value is significantly lower. Imported antistatic agents are more effective than domestic ones, achieving a resistance of 10⁸ even in relatively dry areas. Because the mechanism of action of this type of antistatic agent cannot further improve antistatic performance, antistatic masterbatch is added to facilitate manufacturing, as most plastic raw materials are granular. Its main components are: carrier + antistatic agent + other additives, with the carrier typically being LLDPE resin or other resins.
2. Conductive Plastics: Currently, most conductive plastics in China are made by adding nano-grade conductive carbon black to resin. Varieties include PC, PET, PP, PE, ABS, HIPS, PVC, and various plastic alloys, but most are black. Light-colored ones are rare.
3. Light-colored Antistatic Plastics: These are made by adding nano-zinc oxide whiskers to plastics, which can reduce the surface resistance. Currently, they are expensive and rarely used, but are in the trial and promotion stage. The emergence of antistatic plastics has played a very important role in promoting and developing plastic products, and has also ensured the demand for antistatic products, especially for packaging electronic products and plastic products used in applications requiring antistatic properties. Analysis of the current situation shows increasing demand and a very good development trend!
