Electret production partic carrying relatively high

摘要

Process for manufacturing an electret (defined as an electrified material which has charges of opposite sign on its opposite sides, and in which the electrification extends through the whole volume in contrast to materials in which the charges are only present on the surface) comprising the following steps (1) heating a polyethyleneterephthalate body (I) uniformly to a temp. 80-170 deg.C.; (2) subjecting (I) while at the preferred temp. to an electric field of 0.001-1000 kV/cm for a time of 1 microsecond to 12 hours or more. (3) cooling (I) to -30 deg. to +30 deg.C. whilst in the electric field (4) removing (I) from the field.