Plastic and nonmetallic article shaping or treating: processes – Outside of mold sintering or vitrifying of shaped inorganic... – Including plural heating steps
Patent
1980-01-28
1982-07-20
Lowe, James B.
Plastic and nonmetallic article shaping or treating: processes
Outside of mold sintering or vitrifying of shaped inorganic...
Including plural heating steps
264 22, 310324, 427 12, 427100, 428208, 428209, H04R 1700, H01J 4118, H01J 4122, B29D 724
Patent
active
043407862
ABSTRACT:
A process for making piezo-electric polyvinylidene fluoride (PVDF) film for use, for example, as diaphragms for telephone transmitters, includes the steps of: (a) stretching the melt-extruded film parallel to the extrusion direction with a stretch ratio of about 4 to 1 at about 120.degree. C. to convert it to a .beta. crystalline form; (b) clamping the film between conductive rubber pads to which the polarizing voltage, e.g. 1.3 kv for 12 .mu.m film is applied. While the voltage is thus applied, the film is heated to about 110.degree. C. for 130 mins. and cooled to ambient with the polarizing filed preset; (c) conductive elastomer electrodes are applied to the film in the desired pattern; and (d) the piezo-electric properties are stabilized by heating the foil to about 90.degree. C. for 2 hours.
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