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 modified 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 transferred 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 empirical 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.

Short communications in the form of Letters to the Editor are intended to provide prompt publication of significant new research results and to permit an exchange of views on papers previously published in the JOURNAL. These communications are not submitted to formal review as are research papers, and the editors do not assume any share of the author's responsibility for the information given or the opinions expressed. When work previously published in the JOURNAL is the subject of critical comment, the authors of the original paper are given an opportunity to submit a reply, which will be published concurrently when possible.In continuing the work on the static electrification of filaments, using the apparatus described by Hersh and Montgomery [ 1 ] , certain interesting results have been obtained.Work by Hersh and Montgomery [1] had shown that for insulators rubbed on insulators, the charge generated appeared to be independent of the velocity of rubbing, except where Teflon was involved. In continuous rubbing experiments, however, grounding but not discharging the filaments before the start of each stroke, we have found that velocity has a considerable effect on the quantity of charge developed with most of the insulators tested. For example, increasing the velocity from 2.52 cm./sec. (5 rubs per minute) to 7.65 cm./sec. (15 rubs per minute), doubled the charge for nylon on acetate and acetate on nylon, and increased the charge by 50% for acetate on polyethylene and polyethylene on acetate.In some experiments with polymer blend fibers (polyacrylonitrile-cellulose acetate in different proportions), unusual effects were noticed, the sign of the charge produced being found to change after a certain number of rubs. Extended experiments with continuous rubbing, both with polymer blend fibers and with cellulose acetate rubbed on nylon, suggest that there is a directional effect related to the drawing of the fibers, which governs the sign and perhaps the quantity of charge developed. It is interesting to note that such reversals of sign have been observed in practical setups where assemblies of fibers are run continuously and the static charge developed is measured.Experiments on the discharging of a nylon filament charged by rubbing have been performed, using the radiations of polonium and radium sources. The polonium source was prepared by plating from a hydrochloric acid solution the contents of very old radon capsules. Thus, neglecting the beta radiation of a slight amount of RaE which might have been present and the weak gamma radiation of the polonium, this source was essentially a pure alpha particle emitter. The radium source contained radium in equilibrium with its decay products and thus emitted appreciable beta and gamma radiations as well as alpha particles. It was observed that complete discharge took place when the filament was exposed to the radium source, but when the polonium source was used, an appreciable portion of the initial charge was not removed. This leads us to conclude that, in certain cases...

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