F R A U N H O F E R - I N S T I T U T F Ü R W E R K S T O F F - U N D S T R A H LT E C H N I K I W S
FABRICATION OF ANTISTATIC POLYMER COMPONENTS AND FOILSby integrating carbon nanotubes thin films
info 200-12a
Fraunhofer-Institut für Werkstoff-
und Strahltechnik IWS
Winterbergstraße 28, 01277 Dresden,
Germany
Contact:
Dr. Jens Liebich
phone +49 351 83391-3564
fax +49 351 83391-3300
Dipl.-Ing. Thomas Abendroth
phone +49 351 83391-3294
fax +49 351 83391-3300
www.iws.fraunhofer.de
Motivation
Antistatic or electrically conductive features enable new applications for transparent injection-molded components and polymer foils. Ingeneral, polymers are very good insulators but a sufficient conductivitycan only be achieved by the use ofadditives such as conductive carbonblacks, carbon or metal fibers. The use of additives however, significantlydeteriorates the optical properties of transparent polymers, so that theydo not provide transparency any more.
The procedure, recently developed by Fraunhofer IWS scientists, nowenables to equip polymer surfaces with conductive properties. The
mechanical, chemical and optical characteristics remain largely unchanged in this process.
Antistatic polymer components
To produce an antistatic electricallyconductive polymer component, a less than 100 nm thin carbon nanotube (CNT) coating is depositedon the inner side of the opened mold cavity. A simple post-treatmentremoves disturbing surfactants. During the injection molding processthe polymer compound penetrates the highly porous CNT network andfirmly integrates it into thecomponent’s surface.
Characteristics of CNT thin films
- high transparency (transmission > 90 % in visible light, depending on the applied film thickness)
- high surface conductivity(up to 10-2 S, depending on theapplied film thickness)
- firm embedding of the CNT network into the polymer surface
- high flexibility without losing the conductivity by the networkstructure
Antistatic polymer foils
In order to produce antistatic, respectively electrically conductivepolymer foils, the coating and post-treatment of the CNT films are performed on a temporarysubstrate, e.g. a metal film.Subsequently the coated metal iscalendared with the polymer foil by the use of pressure and increasedtemperatures. Here, the highly porousCNT network is completely integratedinto the polymer surface.
1
Applications
The conductive surface opens up entirely novel application fields forpolymer materials:
- antistatics / avoidance of electrostatic charges
- electrodes for display or lightnings- electrodes for photovoltaics- heatable surfaces- printed electronics- electrostatic lacquer coatings
closeand press
mold
open mold coat andpost-treat
mold
add polymercomponent or
granulate
coatedcomponent
F
F
calendaring separationcoating post-treatment
CNT filmPET foil
temporarysubstrate
F
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Schematic principle of the steps to integrate CNT films in injection molding and roll-to-roll processes
1 Transparent CNT-PET-foil with
antistatic surface in the middle
of the foil
Transmission electron microscope image ofa CNT network
100 nm