Thermally conductive compounds | materials
Today’s more compact and more powerful electronics place new demands on product designers in terms of thermal management. Peter Mapleston takes a look at some of the additives available to enhance the thermal conductivity of polymer compounds
Taking the heat off plastics
Demand for conductive plastics in thermal manage- ment applications continues to rise. There are many examples within LED lighting, automotive, surveillance cameras, IT products, cooling and heating systems where improved thermal transfer materials are required to accommodate increasing temperatures generated by smaller and more powerful electronic components. And understanding among product designers about how plastics can trump metals with greater design flexibility, ease of manufacturing, lower weight and systems cost reduction potential continues to increase.
In line with this, thermally conductive additive options
for plastics compound producers are also expanding. New players are entering the field, and existing suppliers are fine-tuning their offerings. One of the more intriguing new entrants is from Carbodeon. This Finnish company says its nanodiamond materials can have significant effects on the thermal conductivity of thermoplastic compounds when used in small quantities in combination with a conventional thermally conductive filler such as boron nitride, alumina or carbon. Nanodiamonds are synthesised by detonating an
explosive material under controlled conditions to create particles in a very tight and small size range. When coated onto a conventional filler in a pre-treatment
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process - that can be carried out by compounders -they are said to considerably improve the additive-polymer interface, lowering the thermal resistance between the filler particle and the polymer matrix. The nanodia- monds themselves have a thermal conductivity of up to 2,000 W/m.K. “Normally there is a less than perfect interface
between the thermal filler particles and the polymer, resulting in phonon scattering at the interface so that there is a thermal impedance at the barrier,” says CEO Vesa Myllymäki. “By inserting nanodiamond material into these interfaces, there is a much better interface for phonon transfer - this is in part due to the size of the nanodiamond particles and in part due to their surface chemistry, so that the materials wet each other very well.”
The increase in thermal conductivity is typically
between 25% and 100% compared to the use of conventional fillers only (Figure 1). And, because diamond is also electrically dielectric, the Carbodeon technology can also be used to create electrically insulating, thermally conductive compounds for electronics and LED applications. Carbodeon developed the materials with financial
support from the Finnish Funding Agency for Innovation (Tekes). Founded in 2006, the company started to
February 2017 | COMPOUNDING WORLD 45
Main image: Smaller and
more powerful electronic
devices call for plastics that
offer improved thermal
management
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