Measurement of Charge Generated by Friction between Metal and Plastics for Prevention of Occupational Accidents due to Static Electricity

Abstract

In order to prevent occupational accidents caused by static electricity, such as explosions and fires at industrial chemical plants, the suppression of spark discharges of an energy larger than the minimum ignition energy of the flammable material is essential. Static electricity is generated by friction between two different materials, for example, a container or pipe-line and pellets of raw material. Some of the generated charges are relaxed as a result of gas discharge in a micro gap between the materials. Our aim is, therefore, to measure the absolute quantity of the initial charge separation during friction and the relaxation rate due to the micro gap discharge. We developed an experimental setup to measure in real time the charge generated during friction between a metal and a plastic material in vacuum and air. In this paper, the static electricity generated during friction between stainless steel and poly-ethylene terephthalate (PET) are measured. It was found that the static electricity in air is almost one order of magnitude smaller than that in a vacuum. The prevention of occupational accidents and improvement in safety were discussed on the basis of a typical model for an industrial situation with the experimental results in this study.