Functionalized polymers in general are claiming more and more novel applications for example they can function as a metal replacement. 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.
To functionalize an intrinsic isolating polymer high loadings of conductive fillers, like graphite, carbon blacks, CNTs, metals and/or others, are necessary. The mixtures, the so called compounds expose a significant different behavior in processing and in their properties compared to the neat polymer which will be disclosed in the paper. Thus the paper focusses on the development of electrically and thermally very good conductive thermoplastic compounds for bipolar plates in fuel cells, battery stacks or heat exchange applications. For this purpose fundamental basics about percolation and material science are discussed introductory and the unique very high demands while processing compounds with 80 to 90 wt% of fillers will be described in the paper.
By variation of fillers and filling content a specific adjustment of electric and thermal properties can be realized. For example the thermal conductivity of commercially available unfilled polymers like PP or PA is usually between 0,17 and 0,33 W/mK. During the development at ZBT the values for thermal conductivity of polymer-compounds could be increased to more than 30 W/mK what means that they are up to 100 times higher than the conventional unfilled polymer. Also the electrical conductivity of such materials could be increased to more than 100 S/cm.
Besides the compounding process to produce conductive granulates for further processing by injection molding also novel & innovative direct extrusion of semi-finished products like sheet extrusion or a roll-to-roll process for film extrusion of these conductive materials will be presented.
Fig.: Raw materials, conductive polymer compound, sheet extrusion of highly filled compound
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