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event review | Conductive Plastics 2016 Above:


Conductive Plastics 2016 attendees heard experts speak on topics from design through to processing


loading on thermal conductivity. HPF The Mineral Engineers, a division of the


Quarzwerke Group, offers Silatherm aluminosilicate mineral fillers for thermal conductivity improvement with electrical insulation. Péter Sebö, Market Develop- ment Manager, explained that achieved conductivity is affected by filler characteristics, compounding param- eters, and part processing variables. The latest Silatherm products are blends of different particle sizes and the company is also investigating combinations of Silatherm with boron nitride.


Design considerations Several speakers at the conference noted that, when replacing metal with conductive plastics, designers must look outside the box of existing specifications. In many cases, specifications for an application will have been written with the properties of metal in mind, rather than what performance is actually needed. Speakers said it is key to consider the application as a whole, rather than just looking at a datasheet. Conductive plastics can not match the thermal


conductivity datasheet value of metals. Plastics can, however, match the heat exchange performance of met- als, said Renaud Maurer, Senior R&D Engineer at PolyOne, who reviewed the use of thermally conductive polymer compounds for moulded interconnect devices (MIDs). An MID is a functional system in which a circuit trace is applied directly onto a heat sink made from a conductive thermoplastic using a direct metallisation process. The MID can replace an assembled printed circuit board mounted on a metallic heat sink for uses such as LEDs and power electronic modules. Maurer showed that, using an innovative design, a polymer- based MID had been developed that offered a 25% increase in heat exchange compared to the original metal alternative. US-based OutLast Technologies, a subsidiary of


CoorsTek Technical Ceramics, is expanding from textile applications into industrial markets with its Conductive LHS [latent heat storage] materials. These thermal-


70 COMPOUNDING WORLD | November 2016 www.compoundingworld.com


management materials delay or reduce the temperature increase of a system by absorbing and storing latent heat during a material phase change. Different materials act at different phase-change temperatures and can be utilised as alternatives to thermally conductive materials for applications such as LED lighting systems and sleeves for lithium ion batteries. In this latter application area, an LHS composite reduces thermal stress and the heat history from cycling, lengthens battery life due to lower battery temperatures, and improves battery-pack safety by preventing thermal runaway, said Outlast Chief Technology Officer Mark Hartmann. Ted Sidoriak, North America Product Manager at


Lehvoss, described a showcase project that redesigned a flashlight, using a thermally conductive PET polymer, with fins to effectively dissipate heat through the housing to the environment. The material’s flow and adhesion properties were important for filling the fins in the mould. Partners in the project included boron nitride supplier 3M, German PCB producer Haeuser- mann and Finnish injection moulder RF Plast.


Thermal measurement Measuring thermal conductivity is not an easy task and results can vary significantly depending on what test is used. Heng Wang, Senior Product Marketing Specialist at TA Instruments-Waters, explained that different types of instruments and test methods are needed to measure thermal properties of different materials, depending on whether they are insulative or conductive. He explained the science behind thermal conductivity measurement using steady-state and flash diffusivity methods and instruments, and noted that the appropri- ate tool also depends on sample shape and tempera- ture range. Sample reproducibility is another concern— if there is more variability, a larger sample will help give


Typical thermal conductivity values of thermally conductive plastics compared to unmodified polymers and metals


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