In the project, the incorporation of fillers into the polymer was optimized in the Coperion ZSK twin screw extruder to avoid agglomeration and mechanical degradation of the polymer during installation. (Build: Cuperion)

The work focuses on bipolar panels, which are a key component of fuel cell assemblies. In this case, on those versions that are based on heat-related graphite compounds. Extremely high fill levels previously unknown Process engineering requirements. The Stuttgart company provides the technical know-how for the development of machines for complex production.

What are bipolar panels – and what makes them so important?

Bipolar plates made of graphite polymer composites are ideal for portable applications due to their light weight. It combines properties such as electrical and thermal conductivity and gas tightness with a mechanical loading capacity much higher than pure graphite versions. In addition, they withstand the effects of moisture and acidic media at typical operating temperatures over longer periods of time than metallic alloys.

The Stuttgart-based company combines its expertise in manufacturing plastic composites with limited feedstock to prepare mixtures consisting of a very high percentage of graphite and a small amount of polymer. This is intended to lay the groundwork for future upgrade.

What are the obstacles?

“Our main focus is on two particularly critical factors: the high graphite ratios – the project aims to fill levels above 85% by weight – along with the low bulk density require special devices to feed the mixtures into the extruder and to increase the throughput of the potential mass. We want to incorporate these materials At the same time, we are also optimizing the incorporation of fillers into the polymer to avoid agglomeration and mechanical degradation of the polymer during synthesis,” explains Marcus Fiedler, Process Engineering, Head of the Cuperion Chemical Applications team.

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Coperion also provides its own FET technology

Patented Feed Enhancement Technology (FET) is used as the core technology to improve feed behaviour. It is particularly suitable for fine, non-pressurized fillings. The feeding area of ​​the side feeder is equipped with a gas-permeable porous wall. If there is a vacuum outside, part of the air in the mixture is absorbed. This increases the bulk density and therefore the material capacity in the side feeder.

An improved machine concept for the mixture homogenization process was also developed. At the same time, the company uses 3D digital flow simulation (CFD) for virtual and real optimization of the polymer and filler mixing process. Along with the project, Coperion is also developing a built-in quality tool to record process and product fluctuations, which will enable real-time composite quality regulation in the future.

The project is funded by the Federal Department of Economic Affairs and Energy with the acronym GrabaT (Graphite-Based Bipolar Plate Technologies) under code 03ETB028B.

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