Polymers are usually poor heat conductors compared to metals due to the lack of free electrons in polymers. For many applications, both a high thermal conductivity and a high thermal diffusivity yield a more economic production process or increase the technical functionality of polymer components. The most effective way to improve the thermal conductivity of polymers is to add suitable fillers. The aim of this master thesis was to economically optimize the production process of polymer components, which are manufactured by blow molding or injection molding. Increasing the thermal conductivity and thermal diffusivity of the used polymer (high density polyethylene, ʎ=0.44Wm-1K-1) by adding an ideal filler system, the required cooling time is diminished. The selection of the fillers has to consider both technical and economic aspects (low material price). Furthermore, the filler content must not exceed 30 Vol.-%. Moreover, the influence of the fillers on the mechanical properties of the polymer had to be investigated. A three-step experimental design was created. Each step was based on the results of the previous one. In a first test series, the influence of the filler content of cristobalite (SiO2) and montmorillonite (layered silicate), the compatibilizer content, and the compatibilizer type on both thermal (thermal conductivity) and mechanical (Young’s modulus, tensile strength) properties was investigated. The results show an intense increase of the thermal conductivity with rising filler content. Neither the compatibilizer content nor the selected compatibilizer types significantly affect the thermal conductivity. Consequently, a filler content of 30 Vol.-% and no compatibilizer were set. In a second test series, 12 different filler types were screened. This included two-phase systems (polymer + filler) and three-phase systems (polymer + filler 1 + filler 2). The thermal (thermal conductivity, thermal diffusivity) and mechanical properties (Young’s Modulus, tensile strength) as well as the properties of the filler itself (Mohs-hardness, density, price) were determined. Three filler types were found to fulfil the requirements best. Those were compounded with high density polyethylene in a third test series. The 3 batches were injection molded to specimens, which were tested for thermal and mechanical performance. Anisotropic fillers were found to improve the thermal conductivity more than isotropic ones, from 0.47Wm-1K-1 to 4.5Wm-1K-1 compared to 0.77Wm-1K-1 to 1.2Wm-1K-1, respectively. However, due to orientation effects in injection molding the anisotropic fillers decreased the cooling time less than expected. In general, with increasing filler content the compounds become stiffer but more brittle.