materials feature | Thermal conductivity
New CoolFX hybrid fi llers from Momentive provide improvements in physical properties while maintaining thermal conductivity at a lower total cost. Graphs show data of various 5 W/m.K formulations
Improved Impact Improved Tensile Strength
Note: Test data. Actual results may vary Target applications include: LED lighting; consumer
electronic devices; aerospace and automotive cooling systems; motor and battery housings; temperature sensors; and heat exchangers. Momentive produces more than 70 standard and
custom grades of boron nitride powders and hybrid fi llers to meet a wide range of application requirements and has more than 50 years of expertise in the synthe- sis and refi nement of such materials. While much of the attention in the thermally
conductives business is currently on boron nitride, it should not be forgotten that graphite remains an excellent solution in the right circumstances. Graphite, rather like BN, is anistropic and fl aky, so processing conditions are important. Graphite increases the electrical conductivity of a thermoplastic as well as its thermal conductivity, which may be an advantage in some applications and a drawback in others. Graphite it is a lower cost option that BN, so is often the preferred option when electrical insulation is not required. Graphite and carbon producer Timcal says that
graphite is an ideal choice in emerging markets such as LED lamp sockets, heat sinks, and geothermal pipes. The company offers primary synthetic graphites, such as Timrex KS44, and also special expanded graphites like Timrex C-Therm 001, for which it has a patent pending on its easy-feeding characteristics.
Compounders take control Numerous polymer suppliers and independent compounding companies have unveiled new thermally conductive thermoplastics in recent months, many of them aimed at the growing LED lighting market. LED lighting systems are now widespread in
applications such as transportation, and indoor and outdoor living areas. Since the lamps create a lot of
18 COMPOUNDING WORLD | February 2014
heat in a very small area, and because they are leading to the creation of totally new designs in lighting, they have requirements for refl ector and heat sinks that in many cases are best met by thermally conductive thermoplastics. High brightness LED lights are much more effi cient
than incandescent bulbs at transforming electrical power into light, but also generate considerable heat. The LEDs are sensitive to high temperatures, so heat sinks are often used to ensure optimal performance over time. Metal heat sinks, typically made of alumini- um, are common. However, aluminium parts are heavier and more costly to manufacture than specialty polymer solutions. Lehvoss North America, a subsidiary of German
compounder Lehmann & Voss, recently unveiled compounds in its Luvocom range targeted for this market. They offer thermal conductivity ranging from 0.6 to 1.5 W/m.K, have low electrical conductivity, and meet mechanical requirements with a tensile strength up to 55 MPa and impact strength up to 29 kJ/m2
also conform to the UL94 V-0 fl ame resistance rating. Luvocom LED compounds are based on PET and PA 6. In its total Luvocom range, Lehmann & Voss has
compounds based on polymers ranging from PP to PEEK, with varying degrees of thermal and electrical conductivity. The range is topped out in terms of conductivity by a PPS-based compound with a thermal conductivity of 28 W/m.K. This does have an electrical resistance of under 103
ohms though. A grade with a
thermal conductivity of 8 W/m.K has a resistance of over 1012
ohms. PolyOne recently announced that Mars Otomotiv, a
global supplier of advanced lighting systems for the transportation industry, has selected its Therma-Tech thermally conductive polymers to replace metal in the heat sink of LED lighting for construction vehicles,
www.compoundingworld.com
. They
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