materials | Thermally conductive compounds
Figure 4: Thermal conductivity (in-plane and through-plane shown in red) and price trend (shown as broken line) of 20 vol% boron nitride loaded PA6 with 0, 20 and 30 vol% additions of Silatherm aluminosilicate fillers
Source: HPF
energy systems, and joints and seals. According to Sara Ortega, International Sales and
Marketing at Avanzare, the new material has proven to be more efficient than other alternative materials in the market both in thermosets and thermoplastics.
Figure 5: Mechanical values of 20 vol% boron nitride loaded PA6 with 0, 20 and 30% additions of Silatherm aluminosilicate fillers (two different grades of boron nitride were used, with results depicted by the blue and red bars) Source: HPF
minimal effect on the flow (MFI) and mechanical properties of the host polymer. The av-PLAT-70 material is currently being validated
by potential customers in preindustrial trials for various heat management applications. Avanzare cites dissipation devices and cases for electronic devices and engines, heat transfer pipes for solar and geothermal
50 COMPOUNDING WORLD | February 2017
Hybrid solutions Quarzwerke’s HPF division, which supplies Silatherm aluminosilicate mineral fillers, has been studying the performance of combinations of different types of conductive fillers, working with an independent institute to determine how different ceramic and mineral fillers can be combined to obtain optimised properties. “All of these fillers have their advantages and disadvantages for their own and not every sort of requirement can be solved with only one filler,” according to the company. While boron nitride ceramic filler is well known for its high thermal conductivity, HPF points out that it needs to be used at high addition rates, is not cheap, and gives anisotropic properties (most importantly, there are significant differences in through-plane and in-plane thermal conductivity). “The approach to combine Silatherm with boron nitride was to get the best out of two worlds to achieve higher thermal conductivities, still good mechanical properties and lower the compound price all at once,” says Péter Sebö, Market Development Manager at HPF. Polyamide 6 was used as the carrier resin and was filled with 20% by volume of two types of boron nitride. In a second step, Silatherm was added at a loading of 20% and 30% by volume (Figure 4). It was seen that thermal conductivity increased as more Silatherm was added while the compound price decreased (since the overall density and portion by weight of boron nitride decreased). Sebö points out that an effective balance between
filler content and filler grade is needed because particle size as well as filler content influences thermal conductivity. “With the increase of the particle size and decrease of the specific surface area, the thermal conductivity rises due to the reduction of the
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