Electrets
Electrets (formed of elektr- from "electricity" and -et from "magnet") are dielectric materials that have a quasi-permanent electric charge or dipole polarisation. " An electret generates internal and external electric fields, and is the electrostatic equivalent of a permanent magnet. Oliver Heaviside coined this term in 1885. Materials with electret properties were, however, already studied since the early 18th century. One particular example is the electrophorus, a device consisting of a slab with electret properties and a separate metal plate. The electrophorus was originally invented by Johan Carl Wilcke in Sweden and again by Alessandro Volta in Italy.”
"Electret materials are quite common in nature. Quartz and other forms of silicon dioxide, for example, are naturally occurring electrets. Today, most electrets are made from synthetic polymers, e.g. fluoropolymers, polypropylene, polyethyleneterephthalate, etc. Real-charge electrets contain either positive or negative excess charges or both, while oriented-dipole electrets contain oriented dipoles. The quasi-permanent internal or external electric fields created by electrets can be exploited in various applications."
Recent Journal Articles
Formation and Biodegradation of Polyethylene-based Electret Films
(205-211) International Polymer Processing #2 (2011)
Goldade et al, Belarus, showed that the kinetics of biodestruction of polyethylene films, including starch-filled and inorganic saltfilled ones, alters significantly after such film transfer to electret state. (RDC 5/23/2011)