ADDITIVES | THERMALLY CONDUCTIVE


Figure 2: Comparison of thermal conductivity of PA6 compounds containing various Silatherm grades (filler loading 65% by weight) Source: HPF/Quarzwerke


(especially in thermosets), by Al2 O3 when abrasion


is not decisive, or by combinations with high performance fillers such as BN when low addition rates are important. “Nabaltec and other raw material suppliers work intensively on solutions for higher conductivity which are processable and affordable,” he says.


Figure 3: Comparison of abrasive properties of PA6 compounds containing various Silatherm grades (filler loading 65% by weight) Source: HPF/Quarzwerke


discussed results of tests with various TC additives in thermoplastics. It demonstrated how abrasion is higher when particles are smaller, but smaller particles lead to more issues with viscosity and filling levels. “To overcome this abrasion problem, we combined BN and AOH [aluminium oxide hydrox- ide],” he says, pointing out that AOH has sufficient high temperature stability to be used in compound- ing of polymers such as polyamides. Of all the additive systems tested, this combination achieved the highest TC, at moderate filling levels (36% vol) and caused no abrasion (Figure 1, page 21). Ihmels concludes that for many applications


where moderate thermal conductivity is required can be served either by ATH at high loadings


22 COMPOUNDING WORLD | April 2018


Colour counts HPF, which is a division of Quarzwerke, produces aluminosilicate TC additives under the Silatherm brand. At the AMI conference, Péter Sebö, Head of Marketing & Market Development, discussed development work the company has been en- gaged in relating to products for white and colourable compounds. Silatherm 1466 is brighter than the company’s standard Silatherm 1360 but has the same – or in some cases better – technical characteristics due to a slightly different chemical composition. “We can go even lower with the grain size,” Sebö says (D50 for the 1466 grade is three microns versus five microns). “This allows better overall properties of the end compound and the customer can realise white or colourable compounds.” Sebö says HPF has quite a wide range of


minerals that it can play with when it comes to making a TC blend. One of its latest results from this blending capability is Silatherm VP X, an experimental grade, which has a high degree of whiteness and very good technical properties as well as good isotropic thermal conductivity (Figures 2 and 3). “With Silatherm Advance, we already had an interesting white grade, but with the


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