Processing techniques for highly filled polymers
Mario Gillmann, Zentrum für Brennstoffzellen Technik, Duisburg, Germany
Besides the established use of reinforced polymers regarding lightweight designs, functionalized plastics in general are claiming more and more novel applications and do function as a metal replacement. To functionalize an intrinsic insolating polymer, high loadings of conductive fillers, like graphite, carbon blacks, metals, and/or others, are necessary. The mixtures, the so-called compounds, expose a significantly different behaviour in processing and in their properties compared to the neat polymer which will be disclosed in this talk.
Although many applications like the prevention of static charging and heat sink require lower loads of conductive fillers to reach an acceptable conductivity behavior, there are new challenges in terms of higher conductive plastics. Especially the E&E- market or the so-called “green technologies” require highly engineered polymers for many new needs, e.g., a high level of thermal or electrical conductivity in polymers.
Commonly used processing techniques, e.g., compression and injection moulding, offer the possibility to manufacture semi-finished parts and products with functional structures, but there are limitations regarding the product size respectively quantities. The significant change of the rheological behaviour due to the required high filler loads and the enhanced thermal conductivity cause a reduction of flow lengths and support the development of weld lines, especially in an injection moulding process. Furthermore, it takes a higher effort in tooling and costly compression moulding devices with higher cycle times. Thus, injection and compression moulding are suitable for smaller parts and lower quantities as a consequence of discontinuous processing and the intrinsic behaviour of highly filled compounds. But some applications in the scope of fuel cells and batteries strive to lager dimensions and cost-effective products to reach the market launch.
Hence, the development of new continuous processing techniques like sheet/plate extrusion for highly filled polymers will be discussed. For this purpose, fundamental basics about material science are discussed introductorily and the unique very high demands while processing compounds with 80 to 90 wt% fillers will be described in the talk.