TECHNOLOGY | THERMALLY CONDUCTIVE COMPOUNDS B I
Right: Sibelco developed its Boratherm ATH grades to improve thermal dissipation in polymers
ogy is said to ensure good flowability. According to Sibelco, Boratherm SG is specially designed to offer an ultra-low surface area and large particle sizes, making it well suited for formulations needing good flowability. Boratherm SG-E is a demag- netised ATH option intended for applications with higher demands in terms of electrical insulation. Boratherm SA is a spherical alumina with a narrow particle size distribution. “Almost perfectly spherical particles enable optimal packing, material flow and heat transfer,” says the supplier. Combined with a low specific surface area, Boratherm SA’s particle sphericity also allows for good flowability of the formulated material.
Soft solutions Venator Corporation says it is seeing a significant growth in interest in its Sachtolith HDS for polymer based thermal management solutions. Sachtolith HDS is a soft, white zinc sulphide that can improve the thermal management capabilities of polymer systems without adding electrical conductivity. “Growth in consumer electronics, the popularity of LED lighting systems and the need for batteries with better charging power have resulted in a steady increase in demand for additives that can improve the performance of polymers for some time. However, in the last eighteen months, demand in this area has surged. Since the start of 2020, Venator has seen a sharp rise in enquiries
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about its Sachtolith HDS additive,” the company says. “The inclusion of additives with thermo conductive properties – such as Sachtolith HDS - can make a decisive contribution to the formulation and thermal performance of polyamide, polycarbonate or polyester compounds.
Thermal conductivity is influenced not only by the chemistry of the filler itself, but also by its particle size and shape. Good thermal conductivity requires contact between thermally conductive particles.
In addition, the degree of filling required, and the corresponding mechanical stability of the additive can have an impact on thermal performance.” Venator says Sachtolith HDS has a fine and
narrow particle size distribution that can enable increased thermal conductivity with optimised mechanical properties. The almost spherical structure of the individual particles reduces the anisotropy effects of thermal conductivity, so enlarging the working window in the production of components. Thermal conductivity of around 1.2 W/m·K can be achieved in polymer compounds, a value that lies within the target range of applica- tions such as LED lighting systems. “The use of SachtolithHDS additive enables
formulators to retain all the good manufacturing and mechanical properties of glass fibre reinforced compounds and makes the addition of a separate white pigment obsolete,” the company says. “In addition, the zinc sulphide surface of the pigment immobilises any migration of, for example, copper ion, meaning service life and temperature stability is enhanced accordingly.” Imerys Graphite & Carbon says its Timrex
Figure 5: Through-plane thermal conductivity (measured by laser flash) of PS and graphite-PS compounds produced via internal mixer and compression moulding Source: Imerys Graphite & Carbon
46 COMPOUNDING WORLD | August 2021
natural and synthetic graphites and specialty high aspect ratio Timrex C-Therm grades are able to confer high levels of thermal conductivity to polymers. The company says that targets above 20 W/m·K in-plane and 4 W/m·K through-plane can be achieved using the additives while maintaining good processability of the final compound. “In most resin systems, 20% C-Therm loading is sufficient to reach 1W/m·K through-plane thermal conductivity,” says Anna Ellett, Imerys Graphite & Carbon Field Application Engineer Polymers. Imerys Graphite & Carbon supplies graphite solutions with a wide range of morphology and particle size distribution, which enables the fine-tuning of compound properties. This applies
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