Nomex® Electrical Insulation: Wet Resistivity

Nomex® Type 410 has a high electrical resistivity which is maintained even after limited exposure to moisture. This is critical to energizing equipment that has been sitting for long periods of time. In this demonstration, the surface resistivity is tested using a megohm meter. First, the dry Nomex® is tested and shows a full scale reading when the probes are placed on the sample, which indicates the desired insulating properties. After the initial dry test, the Nomex® is briefly soaked in tap water and then partially blotted dry. With the sample still damp, the probes are placed on the sample and the meter still reads full scale, indicating the resistivity is still acceptable. Repeating this test with a non-DuPont aramid, shows that the dry reading yields acceptable results. After the wetting process, the probes are placed on the sample and the reading on the meter shows a lower value than full scale indicating that the sample is conducting electricity between the electrodes. This is a condition which causes equipment failure in real-life applications.