What are Conductive Carbon Blacks and how might I use them in my products?
One of the more innovative uses for carbon black pigments in the plastics industry is to produce conductive or static dissipative products. Since few plastic resins are inherently conductive, it is necessary to add special fillers to the polymer matrix to give them the desired conductive characteristics.
Carbon blacks have proven to be one of the most versatile functional fillers for plastics. In addition to providing electrical conductivity to the plastic compound, they also provide lasting protection against ultraviolet light degradation. Carbon blacks function as a moderately low cost pigment, producing various shades of black in the final product. In many formulations the masterbatch producer can provide a solution wherein several properties are combined in one product.
The selection of the proper carbon black to use in the production of conductive compounds is based on the desired final properties of the particular compound. It is dependent on the specific properties of the carbon black. including particle size, structure, and purity. The chose carbon black can then be combined with a variety of carrier resins, to produce the finished compound.
Requirements for an Effective Conductive Black Compound include:
• Excellent dispersion.
• Integrity of the carbon black structure or network.
• Consistent particle size.
• Specific resistance—High: <10 ohm-cm, General: 10-100 ohm-cm, Antistatic >1000 ohm-cm.
Conductivity is measured by the surface resistivity (SR) of the conductive film. A better conductivity performance for a particular conductive black compound will permit the design engineer to use the appropriate loading of carbon black to achieve the minimum required surface resistivity for the application.
Conductivity is dependent on:
- The polymer matrix
- The type of conductive black
- The concentration of the conductive black
- The dispersion quality of the compound
- The distribution of the conductive black during extrusion
Increased volume conductivity generally means decreased surface resistance. The graph above illustrates the internal resistance of various substances. To reduce internal resistance of a polymer it is quite common to add a conductive substance such as carbon black. The necessary amount varies, depending upon the desired end properties of the polymer film or molded article.
Ampacet Corporation produces a family of high quality, performance oriented, conductive carbon black compounds and masterbatches. Ampacet can also custom engineer products to meet the specific needs of most applications.