Measurement of tribo and corona charging features of materials for assessment of risks from static electricity

Many of the risks from static electricity arise in relation to the maximum surface voltage that may arise when materials are rubbed. This paper describes a new approach for assessing risks in terms of the "capacitance loading" experienced by static charge retained on materials. This involves simultaneous fast-response measurements of the quantity of charge transferred and the initial peak voltage generated. The quantity of charge transferred divided by the initial peak voltage allows calculation of the "capacitance loading." If this is large, then only low surface voltages will occur with practical quantities of charge transfer, and static problems are unlikely to arise from charge retained on the material itself. This approach provides a necessary addition to assessment of materials by the charge decay time when charge decay times are long. Studies show that decay times need to be quite short, 0.2 s, to avoid local high peak surface voltages.