Satellite dishes consisting of highly-conductive compounds
Application

Highly-conductive compounds

Reduced electrical resistance hinders static charging

Compared to other materials, plastics have several advantages. However, they cannot be taken advantage of in certain application fields due to lacking conductivity.

In particular in potentially explosive areas, when packaging and handling electronic components or also when transferring radio signals, the lacking conductivity may result in failure or considerable functional impairment. The danger of electrostatic charging exists.

If materials charged in this manner discharge via spark formation, they can ignite explosive atmospheres such as solvent/air mixes or dust/air mixes. This type of plastics cannot be used for such applications.

Typical areas of application

Plastic plates in a fuel cell consisting of highly-conductive plastic
Highly-conductive joints minimise electrostatic charges for medical devices such as MRI
Conductive plate consisting of highly-conductive compounds for hindering static charging
Fuel cell consisting of highly conductive compounds produced on a BUSS compounding system
BUSS compounding systems for highly-conductive compounds hinder static charging at fuel gas valves

In order to nonetheless use the advantages of these plastics, special conductive additives are added to them. This increases their conductivity considerably or reduces their electrical resistance considerably.

For example, this measure can reduce the electrical contact resistance of PE from 1016 Ohms to < 104 Ohms. The plastics become electrically conductive. If grounded, electrostatic charging can be safely avoided. In fuel cells, for example, highly conductive compounds are used as material for the bipolar plates.

Further insights into our options for the electronics industry

Benefits

BUSS compounding systems for highly conductive compounds offer the following specific benefits

Mixing in the Co-Kneader is independent of the pressure build-up in the downstream discharge unit, allowing an individual optimization of both process steps. This allows processing at low pressure and temperatures as well as optimum granulation, while temperature control remains guaranteed at all times.

The BUSS Co-Kneader guarantees intense distributive mixing, as the superimposition of rotation and axial movement of the mixing and kneading screw causes flow separations and a large number of shearing surfaces, thereby generating cross-channel mixing.

A large number of mixing cycles is achieved with the BUSS multiple-flight Co-Kkneaders in the compounding machinery. The unique screw geometries enable maximized splitting and recombining of the compounds, with numerous striations and excellent mixing over a very short process length.

The moderate shear rates of the BUSS Co-Kneader guarantee controllable shearing and low temperature profiles and demand considerably less of the structure of fibers and highly-structured fillers such as carbon black than other systems. This results in better mechanical and electrical properties, improved flow characteristics and lower consumption of expensive additives.

The processing of a wide range of formulations with the same screw configuration can be a challenge. The BUSS Co-Kneader technology is meanwhile known for this specific capability, thanks to a processing length that is typically half that of comparable systems, moderate and adaptable shear rates and the large flexibility in screw configuration design.

Compounding requirements

of highly conductive plastics

These specific property profiles are achieved in the compounding step. The processing requirements are very demanding. The conductivity values must be guaranteed both at room temperatures and increased operating values.

The highly-structured carbon black, graphite, carbon nanotubes and carbon fibers must retain their structure and be distributed extremely homogeneously in order to form the required conductive network. The polymers used may be degraded as little as possible. The ability to cross-link the compounds may also be a further requirement.

These requirements which in-part run into each other are mastered well, using sophisticated processes.

The BUSS Co-Kneader has proven itself over a long period when compounding these particularly demanding materials. The moderate and uniform, if necessary also specifically adaptable shear rates and with them precise temperature management of the BUSS Co-Kneader play the central role here: in the melting zone only as much energy as required is dissipated without overburdening the polymer components.

The conductive agents are optimally distributed within the shortest process length due to the high flap-die values. At the end of the process, the fibrous conductive materials are added, separated and wrapped if necessary in order to maintain the maximum fiber lengths and to ensure the corresponding properties in the conductive network. This also enables the achievement optimum property profiles for the narrowest processing windows and highest viscosities.

With the two-stage system of the BUSS Co-Kneader, compounding and the pressure build-up step are strictly decoupled. This enables independent optimization of the process steps. The hinged BUSS Co-Kneader housing assures fast access and high system availability.

The modular and therefore adaptable plant structure and the widely supported BUSS process expertise make the BUSS Co-Kneader a very good choice for compounding demanding highly conductive compounds and provide top investment security.

Typical plant layout

COMPEO compounder for compounding highly conductive compounds

Take a look at our typical plant layout for the production of highly conductive compounds in our COMPEO showroom.

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