TECHNOLOGY | THERMALLY CONDUCTIVE COMPOUNDS
Figure 3: Thermal conductivity of carbon black filled PA measured using hot plate method on stacks comprised of samples of different thicknesses. The top image shows the Evonik screening method for evaluating thermal conductivity behaviour using plaques with thickness of 2mm, 4mm and 6mm together to achieve a total thickness in the specimen of 12 mm. The lower image shows thermal conductivity values of 12mm specimens in PA containing conductive black filler that were assembled from 2mm, 4mm and 6mm plaques
Source: Evonik
between the plaques does not necessarily help. Therefore, for hot disk measurement a high thickness specimen is needed to avoid incorrect reading.” Evonik uses laser flash and hot plate methods for measuring thermal conductivity of compounds that contain anisotropic additives. Evonik also offers solid OMS additives that can be applied in-situ with the fillers during compound- ing. These include Tegomer H-Si 6441 P, Tegomer P 121, and the newly developed Tegomer H-Si 6444 P. These additives allow loading levels of fillers to be increased without compromising the mechani- cal properties of the polymer and also improve surface quality and appearance. A further advan- tage of the OMS chemistry is in improving flame retardance in compounds.
In the matrix Huber Engineered Materials commercialised its first products for thermally conductive plastics compounds several years ago. It says that while products in its portfolio, such as aluminium hydroxide (ATH), magnesium hydroxide (MDH) and alumina, all provide good intrinsic thermal conduc- tivities, it has focused its development efforts on further improving the interplay between mineral particles and the polymer matrix. Particle morphol- ogy and packing optimisation, along with state-of- the-art surface modification techniques, has resulted in the development of a complete portfolio of thermal management additives under the TM designation.
44 COMPOUNDING WORLD | August 2021
The company recently supplemented its
Martoxid TM series with the introduction of the Martinal TM and Magnifin TM series. It says the new products close the gap between performance and safety, suggesting a solution for thermally conduc- tive plastics that fulfils the most demanding flame-retardance requirements. For EVs, all three ranges offer solutions for thermally conductive gap fillers and pads, espe- cially for silicones, epoxies, PUs and acrylates, but also for polymer applications. “Martoxid TM and Magnifin TM products not only enhance the thermal conductivity (up to 3 W/m·K) of engineer- ing thermoplastics (for example PA6, PA6,6 and PBT) found in the battery housing, but also provide the highest classifications in flame tests (such as UL-94), even for smallest wall thicknesses,” the company says. Boratherm SG (ATH) and Boratherm SA (spheri- cal alumina) from Sibelco have been specially developed to improve heat dissipation properties in plastics. The materials are thermally conductive and electrically insulative, while particle morphol-
Figure 4: Mineral additives from Huber offer different property balance in finished compounds, including enhanced thermal conductivity Source: Huber Materials
www.compoundingworld.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77
