By nature, plastics are not conductive. The non-conductive nature of plastics is often considered to be a useful property when compared with highly conductive materials like metals. However, it is sometimes useful to incorporate some conductive properties into plastic. The number of applications for conductive plastics continues to grow rapidly. Conductive plastics are easier to paint by electrostatic painting, they protect highly sensitive computer chips, keep plastic surfaces dust free, and reduce static in plastic films.
Below are three basic levels of conductive plastics and how they're achieved:
1. Antistatic - Sterate additives
2. Electrostatic Dissipation (ESD) - Carbon black
3. Electromagnetic Interference (EMI) - Carbon nano tubes or metallic powders
For simplicity, I am going to focus on using carbon black to achieve conductivity. For all of the above additives, dispersion will be the most important factor for achieving a high level of conductivity in plastics. The same is true for carbon black. Carbon black becomes conductive when the loading in plastic is high enough to enable overlapping electron structures to transfer electrons between themselves.
The effectiveness of carbon black in conductive plastics is determined by the particle size, porosity, and structure of the carbon black. Below is a chart that will hopefully make this easier to understand.
To achieve the best conductive results, carbon blacks should impose minimal degradation on the mechanical properties and melt rheology of the carrier polymer. Perhaps most difficult is achieving low compound moisture absorption (CMA). Carbon black absorbs moisture from the environment very quickly and this moisture effects the compound properties very quickly. For high end applications such as conductive plastics and pipe masterbatches, low CMA is extremely important.
An additional point of interest is that the conductivity of extruded products is better than products made by the injection molded process. The reason for this is due to the orientation of the carbon black structures during the injection molding process. Severe orientation creates gaps between carbon black molecules that are too big for successful electron transfer, thus reducing the conductivity of the finished part.
For more information on carbon blacks, please visit:
China Synthetic Rubber Corporation -
Modern Dispersions -
Cabot Corporation -