Method of manufacturing a homopolar electret from a foil

Details Method of manufacturing a homopolar electret from a foil Method of manufacturing a homopolar electret from a foil

1975-03-17

1977-07-26

Lanham, C.W.

Metal working

Method of mechanical manufacture

Electrical device making

307 88ET, 17910041B, 179111E, 361225, B05D 512

Patent

active

040373100

ABSTRACT:
A method of manufacturing a homopolar electret from a foil of a non-polar polymer, preferably TEFLON-FEP or PFA. The polymer foil is formed into an electret by heating it above the transition temperature and below the melting temperature of the polymer under the influence of an electrostatic field of a magnitude such that a homopolar charge is injected into the foil which is greater than the desired value, and the foil then being cooled to room temperature. However, before the transition temperature is reached during cooling, the electrostatic field is switched off so that the charge surplus is thereby removed.
If the foil is disposed between two electrodes, a better result can be obtained by providing the foil with a vacuum-deposited metal layer in contact with the positive electrode during the formation.
The charging time lies between 0.02 secs. and 1 min. and is preferably smaller than 5 secs.

REFERENCES:
patent: 3449094 (1969-06-01), Baxt et al.
patent: 3660736 (1972-05-01), Igarashi et al.
patent: 3885301 (1975-05-01), Murayama

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