Thermally conductive and electrically insulating boron nitride microparticles (BNMPs) has attracted attention for thermal management applications through reinforcing polymers. However when low filler addition has been considered, achieving a proper percolation network to decrease the thermal resistance is not effective. High density polyethylene (HDPE) and polyetherimide (PEI) as a high performance thermoplastic offers significant advantages for advanced applications. Hence, melt-extrusion of CNTs and BNMPs in HDPE and PEI will be achieved by using a single and twin screw extrusion system at moderately high loadings up to 5, 10, and 15% wt. fractions. BN/HDPE and BN/PEI nanocomposites will be manufactured by compression molding to investigate thermal conductivities by flash analysis. Additionally, BN/PEI filaments will be used in a high performance 3D printer to ınvestigate the possibility of printing specific geometries as heat sinks for electronic applications.