Relation of Charge to Frictional Work in the Static Electrification of Filaments

Abstract

A study of the generation of electrical charge on fibrous materials was carried out using the apparatus of Hersh and Montgomery, in which a fiber is held fixed in an insulated lower yoke while a second fiber in a grounded upper yoke is rubbed across it under controlled ambient and mechanical conditions. The original apparatus was modi fied to permit measurement of the frictional work of rubbing as well as the charge. Precautions were taken to discharge both fibers with a radioactive source after each measurement.It was found that, at any one velocity, several thousand rubs were required before steady values of charge transferred and frictional work of rubbing were obtained.It was also found that the velocity of rubbing affected strongly both the charge trans ferred and the frictional work of rubbing, the former being found to decrease and the latter to increase with increasing velocity. This has been explained in terms of local heating, plastic junctions, and material transfer which occur during rubbing. An em pirical relationship relating the velocity of rub, the frictional work of rubbing, and the charge transferred was found to hold in the great majority of the cases examined.From the experimental data obtained it was possible to calculate the mechanical energy expended in any one rub and to estimate the resulting electrical energy. Thus for any pair of fibers under a given set of conditions it was possible to calculate the efficiency of the process of converting mechanical energy to triboelectrical energy. At 30° C. and 33% RH, measured efficiencies were very low (0.00-0.42%); at a very low humidity, efficiencies as high as 2.0% were found.The presence of a lubricant on the fiber surfaces during rubbing was found in most cases to cause a decrease in both the charge and frictional work of rubbing.