Using a Novel Expansion-Die in the Field of Injection Molding for Generating Anisotropic Thermal Conductivity

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Using thermally conductive fillers in polymer-based composites allows for the deliberate adjustment of thermal conductivity for the respective area of application. For instance, LED, photovoltaic sys-tems and microprocessors require materials exhibiting a highly anisotropic thermal conductivity combined with a good electrical insulation. In order to meet these requirements high filler contents are usually necessary. Unfortunately, these high filler contents have a highly negative impact on the processability of the respective materials. One way to avoid this issue is the deliberate orientation of the fillers during thermoplastic processing. Another way to allow for good thermal conductivity de-spite a relatively low filler content is the use of Liquid Crystal Polymers (LCP) instead of conven-tional polymers. Due to their chemical structure, LCP show a particularly suitable behavior as a ma-trix material for generating a high thermal conductivity by means of thermoplastic processing tech-niques. The applicant intends to use a novel expansion die in the field of injection molding to pro-duce sheets with highly anisotropic thermal conductivity and an optimized filler content.Within the scope of this research proposal a novel expansion die will be utilized in order to tailor the alignment of the functional fillers as well as of the LCP matrix. For this purpose, the expansion in-jection molding process shall be used which was previously developed at the IKT. This process al-lows an additional expansion stroke of the mold perpendicular to the flow direction. The filler orien-tation and hence the thermal conductivity of the sheets is to be specifically adjusted as a function of the expansion stroke, expansion speed, mold temperature and injection speed. By varying the pro-cessing conditions, the orientation behavior of both components will be investigated with regards to the proceeding shear and elongational deformation processes.