TECHNICAL INFORMATION

ORMECON - A Conductive Polymer - An Organic Metal

Polymers that conduct electric currents without the addition of conductive (inorganic) substances are known as "intrinsically conductive polymers" (ICP). Polyaniline (PAni) is the first polymer of this kind to achieve unlimited world-wide commercial availability. PAni is the first dispersible ICP and has been developed by Zipperling Kessler & Co. Besides our production in Ahrensburg it is also commercially produced on the basis of a license by Zipperling on a pilot plant by Allied Signal in Buffalo (N.Y., USA). PAni is marketed under the trade name "ORMECONTM".

Physical properties of intrinsically conductive polymers:

PAni is an organic metal. Although its specific conductivity and the temperature dependence of its conductivity are semi-metallic, all other properties, e.g. its thermopower, must be classified as clearly metallic. The conductivity mechanism of polyaniline is of an unmistakeably electronic nature, but is quantum mechanically limited by the very small size of its primary particles (approx. 10 nm), which results in a macroscopically observable reduction in conductivity. On a laboratory scale it is possible to achieve considerably higher conductivities with polyaniline under certain conditions, e.g. 1000 S/cm, but this is not yet possible on a commercial scale.

The specific conductivity of PAni is approx. 5 S/cm. PAni polymer blends may be made with a conductivity between 10-9 and 102 S/cm.

PAni is transparent in thin layers (green).

All intrinsically conductive polymers are absolutely insoluble in any solvents. Neither do they possess a melting point or other softening behaviour. For this reason they cannot be processed in the same way as normal thermoplastic polymers. Zipperling Kessler & Co has therefore developed the dispersible quality ORMECONTM. It can be processed using a variety of dispersion methods.

Chemical properties of intrinsically conductive polymers:

Conductive polymers are essentially different from carbon black. Besides its metallic character, PAni is a redox-active material. In the conductive state, it is green , and may change its colour and its conductivity on exposure to a variety of medias. So it turns yellow under reducing conditions, and blue under oxidizing or basic ones. Both forms are not conductive!

These properties are on the one hand basis for a variety of new applications but may on the other hand also be restrictive.

Polyaniline is a reactive polymer, and as a metal it is nobler than iron or copper. In the electrochemical series it is ranging close to silver.

Polyaniline is a conjugated polymer composed of oxidatively coupled aniline monomers, converted to a polymeric radical cationic salt with an organic acid.

Application fields of intrinsically conductive polymers:

It is recommended that polyaniline should not be used for applications where carbon black or compounds containing carbon black have already proved to be successful. You should rather use and develop the improved properties of this polymer.

The most important properties or combinations of properties are:

  1. reproducible chemical or electrolytic "switching" between differently conducting states of the polymer.

  2. transparency in thin layers

  3. colour and colour change in chemical or electrolytic environment

  4. high specific conductivity at saturation concentration, therefore good shielding against electromagnetic interference (EMI)

As a result of these advantages over carbon black the following applications are already used commercially, are undergoing pre-commercial trials or are at the development stage:

  • Coating of films, semi-finished articles and injection molding products with PAni dispersion paints for getting transparent, permanently antistatic products.

    • the antistatic behaviour is independent from moisture and can be tuned in a wide range

    • there are products available also for printing (e.g. of labels)

    • water borne systems are under development

  • Corrosion protection by passivation

  • "Smart" windows

  • Dispersions of pure polyaniline in organic solvents are mainly being used in research for preparing defined pure PAni coatings

  • Sensors

  • Membranes for gas separation

  • Electrochromic displays

  • For EMI shielding we are performing research in order to increase the conductivity of Pani and ist blends significantly; we have some success in laboritory scale, but are not yet ready for commercial tests.

Scientific literature and additional reading material is available on the individually listed basic properties of polyaniline.

Applications technology information is to be found in these technical data sheets:

ORMECONTM is a registered trademark of Zipperling Kessler & Co., Ahrensburg. CORREPAIR and CORRPASSIV are in the registration process for Zipperling Kessler & Co..

Position: August 1995

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