Surface resistance lies in the desired range.
A composite material consisting of polycarbonate filled with copper oxide has been found to be suitable as an antistatic material. This material was developed to satisfy a requirement for an antistatic material that has a mass density less than that of aluminum and that exhibits an acceptably low level of outgassing in a vacuum.
Polycarbonate was chosen as the matrix material because it was known to satisfy the low-outgassing requirement. Copper oxide was chosen as the electrically conductive filler material in order to obtain surface resistivity in the desired static-electricity-dissipation range between about 105 and 1011 ohms per square. (Materials with lower surface resistivities are regarded as conductive; materials with surface resistivities greater than about 1012 ohms per square are regarded as insulative and thus not suitable for protecting items sensitive to electrostatic discharge.)
A specimen of the copper oxide-filled carbonate material was subjected to a parallel-bar-contact surface-resistivity test and a static-discharge test at a temperature of 22 °C and relative humidity of 50 percent. The specimen was found to have a surface resistivity of 109 ohms per square on its rough side and 1010 ohms per square on its smooth side. The time for discharging from a potential of 5,000 V to 500 V was measured to be about 0.1 s, and there was no measurable charge left after 5 s. These measured characteristics are well within the acceptable ranges for an antistatic material according to applicable NASA and military standards.
This work was done by Michael Kovich of Lockheed Martin Corp. and George R. Rowland, Jr., of Hernandez Engineering Inc. for Johnson Space Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Materials category. MSC-23356.