Thermal conductivity | materials feature
Peter Mapleston reviews recent developments in thermally conductive additives and compounds which are improving heat management in LED lamps and a growing range of other applications
Cool things down with conductive compounds
The increasing use of electrical components with high energy density has heightened the need for materials that provide effi cient dissipation of the heat produced. LED lighting, which is growing at a dramatic pace, provides the most obvious example of this trend, but numerous other electronic and electrical components can also benefi t from thermally conductive plastics that can be moulded cost-effectively into shapes that maximise their potential. Heat conductive additives differ widely in price and
performance, so users need to be sure they know what they need. The use of metallic fi bres and powders is quite widespread where a high degree of thermal conductivity is required, but these products also increase electrical conductivity of course, and this may not always be desirable. As a result, a growing number of mineral fi llers, which are natural electrical insulators, are gaining a foothold in the market. A potential downside is that they often need to be used at high addition rates – possibly close to 60% – which can have a signifi cant impact on the mechanical properties of fi nished parts.
Mineral movements HPF - The Mineral Engineers, a division of Quarzwerke, began marketing a range of Silatherm aluminosilicate
www.compoundingworld.com
fi llers two years ago. It says that they generate a signifi cant increase in the thermal conductivity of thermoplastics and thermosets. “The values measured in polyamide show that
through the use of our Silatherm aluminosilicate grades thermal conductivities of up to 2.3 W/mK can be achieved and that the mechanical properties remain at a very good level for these high fi ller proportions,” the company claims. By comparison, unfi lled PA 6 has a thermal conductivity of 0.3 W/mK. Market development manager Klaus Berger says that HPF has very fl exible production that enables it to obtain precise particle sizes and particle size distribu- tion. The larger the grain size, the higher the abrasion during processing. HPF grades have a Mohs hardness of 5-6, which is similar to that of glass fi bres. This compares with 9-10 for aluminium oxide, which is another contender in this market. HPF applies different surface coatings according to
the host polymer. Berger says the strongest demand from compounders is for Silatherm grades compatible with polyamides, but recently there has been a growth in interest from companies producing polypropylene compounds. HPF is currently carrying out trials on grades compatible with PP. Silatherm provides approximately the same level of
February 2015 | COMPOUNDING WORLD 17
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