A Standard proposed for assessing the electrostatic suitability of materials

The suitability of materials to avoid risks and problems from static electricity has traditionally been assessed by measurement of resistance. This is not suitable for many materials. Corona charge decay provides a very appropriate approach for assessing a wide variety of materials on the basis that if charge can dissipate over the surface in a short time compared to the time taken to separate rubbing surfaces then there will be no influence from retained charge on items nearby.Materials such as the fabrics for cleanroom garments (that are basically polyester with some pattern of conductive thread) often fail resistance and also charge decay testing—notably where the conductive threads are ‘core conductive’. However, if the capacitance experienced by surface charge to the threads is high then the surface voltage can be suppressed so that no significant surface voltages arise and little risk can arise.The Standard proposed combines corona charge decay measurement with measurement of the influence of the capacitance experienced by surface charge. This covers many aspects, but not all, of the electrostatic risks and problems from materials.