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Thermally conductive | materials


compound producers a number of initial formulations are ready (although there is still space for improve- ment) but the market demand is still relatively low,” Bonacchi says. “Imerys can offer primary synthetic graphite with outstanding through plane thermal conductivity and especially designed primary synthetic or natural graphites for high in-plane thermal conduc- tivity” (see Figure 3). Bonacchi notes that primary synthetic graphite has


the advantage of high purity, making it especially suitable for sensitive materials in which transition metal ions can catalyze polymer degradation. Imerys also offers two grades, C-Therm001 and C-Therm011, that are easy to feed and which he says are able to deliver thermal conductivity at lower loadings than standard graphite. “Although graphite is already an extremely light


additive, for critical applications such as automotive lamps, where weight saving can be of utmost impor- tance, C-Therm can decrease further the compound density,” Bonacchi says. He also says that, during the company’s participation in the European Union-spon- sored four-year NanoMaster Project, which ended last year, Imerys developed a new easy feedable thermally conductive additive called C-Therm301, which provides good thermal conductivity with improved mechanical properties.


The aim of the NanoMaster Project was to develop the knowledge-based processing methods required to up-scale the production of graphene and expanded graphite reinforced thermoplastic masterbatches and compounds and, ultimately, enable its industrial commercialisation in Europe. The work focused on developing processes for large scale rapid production of graphene reinforced plastic intermediate materials for integration into current conventional and additive manufacturing processes.


The project organisers said that while graphene


reinforced polymers have been demonstrated at lab scale in both Europe and the USA, and it has been shown that very low loadings of graphene can have a dramatic impact on the mechanical and physical properties of the polymers it is added to, industrial compounding processes have only so far been devel- oped in the US (where Ovation Polymers offers gra- phene thermoplastic masterbatches and compounds based on graphene from XG Sciences.) Imerys is also promoting extremely large fl ake synthetic graphites, such as KS 150-600SP, which behave very differently from large fl ake natural graphite (Figure 4). “This material forms compounds with very high through-plane thermal conductivity and can be useful for cooling pipe applications or applications in which high


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through plane thermal conductivity is needed,” Bonacchi says. But he does also note that, due to the large particle size, mechanical properties can be reduced.


Improved isotropy Among the major producers of thermally conductive compounds, Lanxess says the Durethan reinforced polyamide 6 compounds that the company introduced at K 2013 conduct heat effi ciently while at the same time being electrically insulating. Their thermal conductivity lies between 1.0 and 2.5 W/mK. The fi rst representa- tives of the line are two easy-fl ow types, Durethan BTC65 H3.0 EF and BTC75 H3.0 EF. Their thermal conductivity is based on reinforcement with 65 and 75% by weight of a mineral, which the company does not


May 2016 | INJECTION WORLD 51


Figure 3: In-plane and through-plane thermal conductivity of injection molded HDPE plaques loaded with different Imerys graphite grades Source: Imerys


Figure 4: Through-plane thermal conductivity versus loading for compression moulded PP homopolyer plaques containing different graphite grades Source: Imerys


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