COMPOUNDS | ELECTRICALLY CONDUCTIVE
Right: Avient says its latest Stat-TechTPEs are suitable for applications including radar units, sensors and camera systems
belts,” says Matt Mitchell, Director of Global Marketing, Specialty Engineered Materials at Avient.
In addition, Avient says Stat-Tech TPEs offer benefits compared to silicone and thermoset rubber, including simplified manufacturing due to single-step fabrication, greater design freedom, and the ability to use two-component overmould- ing directly onto polymer substrates. Six standard grades are currently available, ranging in hardness levels from 40 – 85 Shore A, but formulations can be customised and include food contact compliant grades.
Below: Cabot produces an extensive range of electrically conductive compounds and master- batches
Storage solutions Increasing demand for clean energy generated by intermittent sources, such as solar panels or wind turbines, means there is a real need for safe and efficient energy storage systems. One of the technologies under development for this is the redox flow cell battery. Similar in some ways to proton exchange membrane (PEM) fuel cells, redox flow batteries are composed of cell stacks, within which one of the main components is the bipolar plate. Often made of thermoplastic or thermoset composites, the bipolar plate requires a high electrical conductivity which, in the case of poly- mer-based solutions, is achieved using a high carbon loading. “For redox flow cell batteries bipolar plate, electrical resistivity needs to be in the range of 1 Ω.cm,” says Jérôme Crépin-Leblond, R&D Group Leader Additives for Conductive Plastic at Imerys. “Such a level of conductivity is not possible to achieve while maintaining sufficient processability with carbon black only. To meet the conductivity target, blends of Timrex synthetic graphite KS44 and Ensaco 250G conductive carbon black can be used with a total loading in the range of 50%. The benefits of using a mix of
medium sized Timrex synthetic graphite and Ensaco conductive carbon black include good processability and high purity.” Crépin-Leblond says conductivity targets for fuel cell bipolar plates are much more challenging, requiring volume resistivity below 0.05 Ω.cm. “To meet such levels, higher loading of graphite is needed, up to 80-85%, either in thermosets or in thermoplastic formulations. Imerys offers a portfo- lio of high-purity graphites with optimised particle size distribution for highly loaded polymer com- posites such as Timrex KS5-75TT. To further improve electrical conductivity, Ensaco 250G conductive carbon black is added at limited loading. By replacing the graphite by up to 7%, it is possible to reduce resistivity by a factor of four and optimise processing during compounding.” Energy storage systems are also an area of
interest at US-based Insight Polymers & Com- pounding, according to AJ Pasquale, Director of Operations at the specialist compounder. “In the past year, we’ve been contacted by several companies interested in novel conductive plastics for energy storage.” Insight Polymers is evaluating additives such as
recycled sub-micron carbon fibres for their perfor- mance in energy storage. “Companies are making big investments in producing conductive carbon- based materials,” says Jeremy Lizotte, Insight Polymers Director of Innovation. “We offer electrically conductive materials based on high temperature, high performance resins. These are proprietary products,” he says. “Electrical conductivity is in the context of what the ultimate device requires, whether it is static conductivity, bulk conductivity, RFI, or the thin film electrodes that seem to be the biggest challenge. We’re always going to have to work with the end-user to customise and match their requirements, and every customer’s needs vary.”
40 COMPOUNDING WORLD | January/February 2024
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www.compoundingworld.com
IMAGE: CABOT CORP
IMAGE: AVIENT
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