There are two main reasons to use conductive plastics:
- Conductive plastics prevent ESD (electrostatic discharge)
- Conductive plastics provide EMI (electromagnetic interference) shielding
Rebling is experienced in molding many thermoplastic materials with conductive additives. Usually the base resin (such as polypropylene or PPS) is compounded with stainless steel fibers or carbon powder or fibers to meet a desired resistivity of the material.
Conductive plastics for ESD
Electrostatic discharge can be a problem in sensitive electronic assemblies as well as paper and textile processing applications which generate a lot of static electricity. Traditionally, metal components have been used to prevent the discharge of static electricity. However, in many cases complex shapes are too expensive to machine or impractical to stamp. A conductive plastic solves these issues, while also saving weight.
Conductive plastics for EMI shielding
EMI shielding is important in systems where sensitive electronics can be affected. It is also important in electric vehicle applications where EMI can cause a safety hazard. Again, EMI shielding is traditionally accomplished with metal components. However, molding conductive plastics have the same advantages of lower weight, cost and the ability to make complex shapes. Designing for EMI shielding in electrical systems can be tricky. Rebling recommends extensive EMI testing when using conductive plastics for shielding. With EMI shielding, theory doesn’t always predict success, and the effectiveness of shielding must be proven through testing.
Another option for both ESD protection and EMI shielding is conductive plating. Some plastics can be coated or plated with conductive metals to serve the same goals. Typically this is a more expensive option, but may be more appropriate in certain applications where parts may need to be both conductive and non-conductive.