Electrification due to the separation of materials

Electrification due to the contact and separation of materials is an old and familiar phenomenon which has been both a source of interest and a hazard to man and yet has made possible a number of technological advances. The effects of separation electrification are particularly important for those dielectric materials which have a long charge relaxation time. A separation charge of only one electronic charge for every 6 × 10⁴ surface atoms is sufficient to cause air breakdown. Owing to the minute quantity of charge which produces macroscopic effects, progress in controlling separation electrification has been slow. With the increasing availability of instrumentation, measuring techniques, and many synthetic materials, renewed interest and progress toward understanding separation electrification can be expected.