COMPOUNDS | ELECTRICALLY CONDUCTIVE
equipment on board each, has led to the require- ment for EMI shielding in electronic parts to ensure that neighboring systems do not interfere with one another when sending and receiving electronic signals. EMI shielding requires not only high conductivity but also the ability to miniaturise components, which calls for superior mechanicals. “Cabelec XS6325A conductive concentrate allows nylon compounders to tailor the electrical performance of compounds for ESD or EMI applications,” says Santiague Pierre, Global Application Lead Masterbatch and Conductives, at Cabot Corporation. “This conductive concentrate is so versatile that customers can add glass fibre, plasticiser, flame retardant or impact modifier to create more functionality to their material.” At Imerys Graphite and Carbon, Anna Ellett,
Field Application Engineer Polymers, sees a growing interest in EMI shielding compounds for applica- tions such as 5G technology and automotive driving assistance systems, where factors such as their low weight and high corrosion resistance compared to metal-based systems play an important role. For such applications, the company offers its Ensaco conductive carbon blacks, Timrex synthetic graphites, and specialty high aspect ratio Timrex C-Therm graphites as ways of achieving the
required combination of high electromagnetic signal attenuation, high thermal conductivity and easy processability. Ellett highlights Ensaco’s combination of high
purity, high structure and low surface area, which guarantees low moisture pick-up as well as easy dispersion. She says this makes it possible to reach high levels of electrical conductivity at low load- ings. Meanwhile, Timrex C-Therm graphites, with their extremely high aspect ratios, are designed for applications requiring high electrical and thermal conductivity at low carbon contents. She says a synergistic effect on electrical conductivity can be obtained when blending Timrex C-Therm graphites and Ensaco conductive carbon blacks. “For example, a 50% Ensaco 250G/ 50% C-Therm blend enables reducing volume resistivity by a factor of four compared to a formu- lation with Ensaco as single additive,” she says (Figure 1). This is reflected in superior levels of EMI shielding (Figure 2). At Orion Engineered Carbons, Kevin Milks,
Market Manager for Polymers and Batteries in North America, reflects on the effects of consum- ers’ concerns about fuel prices and climate change on increased demand for electric vehicles (EVs), and the role of conductive polymers to enable aspects of EV technology. Milks says that last year, in his region, there were
indications that more than 50% of car buyers would consider purchasing an EV. The trend has been assisted not only by fuel, climate, and sustainability concerns, but also by the growing availability of EVs, including versions of extremely popular models such as the Ford F-150 truck (the electric F-150 Lightning is set to go on sale this spring). Conductive thermoplastic compounds play a
Figure1: Volume resistivity of PP compounds containing different carbon black blends Source: Imerys Graphite & Carbon
role in improving EV performance but compound- ers face some new challenges. “Thermoplastics polymer compounders are very familiar with converting carbon black and relevant polymers into conductive compounds,” says Vasanth Naray- anan, Orion Polymers Technical Market Manager, “but these EV applications require higher black dosages or higher surface-area blacks to impart electromagnetic interference (EMI) shielding properties.”
Figure 2: Shielding effectiveness of PP compounds containing different carbon black blends Source: Imerys Graphite & Carbon
48 COMPOUNDING WORLD | February 2022
Shielding solutions Shielding to prevent interference with neighbour- ing electronic devices during operation and charging, requires a resistivity of 1 to 500 ohms/ square in plastics covers, Narayanan says. Higher surface area blacks yield lower resistivity at a lower dosage, but higher surface area blacks are more
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