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

jens.liebich@iws.fraunhofer.de

Dipl.-Ing. Thomas Abendroth

phone +49 351 83391-3294

fax +49 351 83391-3300

thomas.abendroth@iws.fraunhofer.de

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

++

+++

++

++

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