Cotton as an Electret

Abstract

Research to enhance the storage of electrical charge in lint cotton led to imparting electret-like properties to cotton fibers. An electrostatic field introduced stored, oriented charges within a bundle of cotton fibers. The threshold values of temperature, time, and electric field for production of cotton electrets are defined, and specifications for measuring charge-density distribution are presented. The electret nature of the phenomenon is substantiated by findings that cotton fibers exposed to electric fields at elevated temperatures show long-term, charge-retention properties that are enhanced by short-circuiting. These fibers also display a tendency to a charge-polarity reversal after being removed from the electric field. Furthermore, the waxes native to the single fiber seem to be the basis of this new cotton property. These waxes are related to one of the best known electret materials—carnauba wax. A similar effect with analogous characteristics has also been produced in polyester fibers. With both fibers the effect is less than that possessed by ideal electrets.