In our previous post, we discussed the application of potting and encapsulating using urethanes and epoxies. When choosing the proper urethane or epoxy for an electrical application, there are some important considerations to keep in mind. In this article, we will discuss those considerations and how they apply to the world of urethanes and epoxies.
Here some examples of electrical applications using urethanes and epoxies:
The 3 most commonly sought after resins for electrical applications can be classified as electrically conductive, electrically insulative, and statically dissipative.
Electrically conductive materials have a low electric resistance and electrons flow easily across the surface or bulk of the material. Charges go to ground or to another conductive object that the material contacts. These materials have a surface resistivity less than 1 x10^5 Ohm/sq or a volume resistivity less than 1 x 10^4 Ohm-cm. Electrically conductive resins are typically filled with metallic or conductive particles.
Electrically insulative materials prevent or limit the flow of electrons across their surface or through their volume. Insulative materials are difficult to ground and have a high electrical resistance. Static charges remain in place on these materials for a very long time. These materials are defined as having a surface resistivity of at least 1 x 10^12 Ohm/sq or a volume resistivity of at least 1 x 10^11 Ohm-cm.
Statically dissipative materials have a surface resistivity equal to or greater than 1 x 10^5 Ohm/sq but less than 1 x 10^12 W/sq. They have a volume resistivity equal to or greater than 1 x 10^4 Ohm-cm but less than 1 x 10^11 Ohm-cm. For these materials, the charges flow to ground more slowly and in a somewhat more controlled manner than with conductive materials.