Heat conductive thermosets for the injection molding process

Nowadays, heat conductive polymers show potential for new applications in different areas especially to dissipate heat in electronic devices. The processing by injection molding is particularly suitable for an efficient large-volume production of multifunctional components such as required for automotive and electronic industry. A thermosetting polymer matrix exhibits the potential to reach a high filling degree due to generally low viscosities of resins. The purpose of this study was the development of a heat conductive thermoset which is processible by injection molding. Therefore, a molding compound consisting of an appropriate resin, functional fillers and a reinforcing material had to be compounded. In this study, low-cost ceramic fillers and glass fibers as reinforcement were filled into an epoxy resin by compounding the materials with a twin screw extruder in order to reach an electrically insulating composite with high thermal conductivity. The epoxy resin Epoxidur^® from Raschig GmbH was chosen as the appropriate matrix material due to a low viscosity and slow curing speed. A filling degree totally up to 60 vol.-% was realized. The flow and curing behavior of the material was investigated with a kneading test. The material was processed to tensile bars by injection molding and the mechanical properties of the material were investigated by tensile and bending tests. Due to shear forces and the high filling degree of the abrasive ceramic filler the glass fiber (GF) length decreased during the compounding. The thermal properties of the material were also investigated by measuring the heat conductivity of the material.