ADDITIVES | THERMALLY CONDUCTIVE
conductivity to polymers. “With these high perfor- mance thermally conductive additives, targets above 20 W/m.K in-plane and 4 W/m.K through- plane can be achieved while maintaining good processability of the final compound,” Ellett says. “In most resin systems, 20% C-Therm loading is sufficient to reach 1W/m.K through-plane thermal conductivity.” C-Therm can also be added to boost the thermal conductivity of standard graphites. “A synergistic effect on thermal conductivity has been observed by blending C-Therm and graphite with a significant increase in in-plane as well as through-plane thermal conductivity,” Ellett says. “For example, substituting as low as 5% graphite with 5% C-Therm enables an increase in thermal conductivity of around 25% in the through plane direction and of around 20% in the in-plane direction [Figures 1 and 2].” According to Imerys, C-Therm can be used to boost thermal conductivity of compounds in combination with other conductive additives, such as conductive minerals, at low loading level to maintain electrical insulation and at higher loading when high thermal conductivity targets need to be achieved.
High expectation “Market expectations are high but still the
requests for thermally conductive plastics com- pounds remain rather low,’ says Christine Van Bellingen, Business Development Manager, Conductive Compounds, at compounding com- pany Witcom Engineering Plastics in The Nether- lands. “Struggling for raw materials supply was probably the major concern in the market, delaying the start of innovative projects requiring thermal conductivity. Sustainability concerns should, however, bring back the interest, knowing that replacing metal for light-weighting will contribute to lower energy consumption and all in all, lower carbon footprint.”
Figures 1 and 2: In-plane (left chart) and through- plane (right chart) thermal conductivity (measured by laser flash instrument) of a graphite-PP compound showing effect of addition of 5% C-Therm high aspect carbon from Imerys. All compounds produced in an internal mixer and compression moulded.
Source: Imerys Graphite & Carbon
48 COMPOUNDING WORLD | August 2022
www.compoundingworld.com
EVs are expected to place renewed focus on
weight reduction. “The minor space available and high weight of EVs will push for new plastics developments involving thermally conductive or EMI shielded thermoplastic compounds, for ECU housings, battery cooling or LED lighting for instance. Getting a better heat dissipation can also help selecting other plastics with lower carbon footprint.”
Another compounder, Tisan Engineering
Plastics in Turkey, says the thermally conductive compounds it has developed are proving them- selves in applications where metals and ceramics are disadvantaged. “Compounds have improved thermal conductivity 50-100 times that of conven- tional plastics,” says Binnaz Coşkunkan, R&D Executive at the firm. It has developed compounds based on polyamides and thermoplastic polyesters. Meanwhile, Radical Materials in the UK pro- duces thermally and electrically conductive compounds branded Konduct. Technical Director Chris Vince says there are many factors that need to be considered when selecting an additive/ polymer system to meet the required performance portfolio. “These include particle geometry/aspect ratio and size, electrical properties and addition rate. Very specific blends of additives can often be tailored to optimise thermal conductivity and cost of the final compound and further modifications can also be made to minimise the effect of the often high additive content on mechanical and processing performance.” Vince says a wide range of polymers can be
offered with enhanced thermal conductivity, with typical values of 1-2W/m.K through-plane and 5-20W/m.K in-plane being achievable. Like Van Bellingen at Witcom, he says the use of such materials in thermal management situation is still not mainstream though and, echoing comments from both her and Tisan’s Coşkunkan, says strong
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