COMPOUNDS | ELECTRICALLY CONDUCTIVE


properties for each application (the company does not disclose which additives it uses). The range of conductivity typically is 106


to 109


Ohm and even conductivity is claimed in all three planes, allowing predictable end-use part performance. Materials are also said to offer high impact strength, allowing use for housings in harsh environments. Further products offering high-strength and stiffness are available based on the use


O N


Above: Several suppliers of conductive additives are targeting applications in FFF 3D printing filaments


of CNTs and selected carbon fibres in combination with additives such as minerals,


according to Thomas Collet, Director Marketing, Business Unit Customised Polymer Materials. “By using these technologies in combination with special fibres (steel and carbon), a portfolio of EMI shielding compounds has been developed,” he says. Production of electrically conductive com- pounds based on polymers ranging from polyole- fins up to high end engineering plastics, and using various conductive additives, is a key strength of specialty custom compounder Witcom, which is a member of the Wittenburg Group. “We are very much accustomed to compound with conductive carbon blacks in our plants in the Netherlands and in China but can also select permanent anti-static additives to produce coloured conductive com- pounds,” says Christine Van Bellingen, Business Development Manager, Conductive Compounds. “Over the last year, we fulfilled several requests to meet stringent ATEX requirements (black or col- oured materials), coupled for instance with high impact, good flame retardancy and UV stability properties, mainly for personal protective equipment


and safe handling of compressed gas,” she says. Witcom expects EMI shielding plastics to gain momentum due to the growth in e-mobility and lightweighting megatrends, according to Van Bellingen. “However, the market indicators tell that the older, traditional EMI shielding plastics solu- tions are not attractive enough to replace metal because they are too expensive or based on non-environmentally friendly additives,” she says. “We have developed cost-effective, non-toxic EMI shielding compounds that can match high attenuation at high frequency (up to 100 dB between 4 to 40 GHz) and medium attenuation at lower frequency (up to 30 dB between 1 kHz and 2 MHz),” she says, adding that those figures are based on PA6 compounds and a sample thickness of 2mm. Compounds can be used to produce light- weight housings that match new e-mobility targets, with shielding effectiveness of 40 to 60 dB.


CLICK ON THE LINKS FOR MORE INFORMATION: � www.cabotcorp.com � www.imerys-graphite-and-carbon.com � www.orioncarbons.com � www.premixgroup.com � www.tisan.com.tr � www.ocsial.com � www.graphmatech.com � www.avanzarematerials.com � www.nanocyl.com � www.carbonx.nl � www.apply-carbon.com � www.lati.com � www.lehvoss.de � https://wittenburggroup.com/witcom/


Fraunhofer composites aim at metals


Fraunhofer ICT is developing electri- cally conductive polymer composites that it hopes could displace metals in some applications where relatively low currents are used. The institute says that the technology could be used to eliminate the use of polymer- metal combinations, which can cause problems in recycling due to the need for disassembly, and avoid the need for cabling in some applications. Two-component injection mould- ing and additive manufacturing methods have been used to produce conductive paths within parts. For each technology, special conductive


60 COMPOUNDING WORLD | February 2022


composites have been developed and appropriate processing param- eters determined. Several demonstration parts have


been produced. One example is a pre-assembled ABS insert with an LED that is mechanically and electrically connected using a printed conductive material (a PC/ABS compound containing carbon nanotubes). A resistivity of 1 ohm.cm was measured in a single conductive layer 200 microns thick. A stack of three layers was printed for connecting the LED with a USB power supply. Another potential area of applica-


tion for conductive composites is redox-flow battery bipolar plates, which separate the electrolyte flow in the individual electrochemical cells and enable the flow of electrical current from one to the next. The electrolytes in redox-flow batteries are highly acidic, so the conductive component is carbon rather than metal-based. Composite parts combine relatively low filler levels, and therefore a relatively low melt viscosity, with a 4-7 S/cm through- plane conductivity said to be well suited to the application. � www.ict.fraunhofer.de


www.compoundingworld.com


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