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Process-Induced Property Modification and its Numerical Prediction

Thermal conductive plastics are a type of plastics, which are filled with conductive fillers to increase thermal conductivity. They are mainly used to manage the temperature in electronic components or as heat exchangers. In these applications the heat often has to be conducted through the thickness of the thermal conductive plastic part. These parts are typically thin-walled. Unfortunately, literature shows that the through-plane conductivity is low in thin-walled parts. This effect results from a lack of orientation of thermal conductive fillers in thickness direction. Conventional processing techniques like injection molding or extrusion instead orient fillers mainly in flow direction. Low through-plane conductivity in thin-walled parts is an urgent problem, because high filler content has to be used to increase thermal conductivity.

Based on this problem an alternative processing is presented in this work, which increases through-plane conductivity significantly. In this process divergent elongational flows are induced to re-oriented fillers. By using elongational flows the through-plane conductivity increases by the factor of 2–3, when filler content is kept constant or the filler content can be reduced by more than 40 % without decreasing through-plane conductivity. A reduction of filler content is beneficial in case of material costs, be-cause thermal conductive fillers are more expensive than technical plastics.

The key for optimizing thermal conductive plastics is an improved processing, which orients the fillers more efficiently. Thus, the effect of divergent elongational flows on the filler orientation and on the obtained through-plane conductivity is evaluated by using a process simulation approach. To increase the accuracy of simulation, the common Folgar Tucker model is verified on its applicability on platelet-shaped fillers. Moreover, the necessarily model parameters are determined. Experimental validation show good results of the Folgar Tucker model when using filler specific interaction coefficients.

Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Author
 Otto Skrabala

Otto Skrabala
Institut für Kunststofftechnik
Universität Stuttgart

Information

Free keywords: thermal conductive plastics, thermal conductivity, simulation, filler orientation, Folgar Tucker, plateletshaped fillers, extrusion, process depended properties, Phan-Thien, Hatta-Taya
Institute / chair: Institut für Kunststofftechnik der Universität Stuttgart
Language: German
Technical consultant for expert services: Prof. Dr.-Ing. Christian Bonten (Betreuer), Prof. Dr.-Ing. Dietmar Drummer
Publication year: 2016
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de

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