Thermoset-bonded injection-molded magnets with defined structure of magnetization

• Applicant: Professor Dr.-Ing. Dietmar Drummer
• Subject Area: Plastics Engineering
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 448366335

Polymer-bonded permanent magnets are composite materials consisting of a polymer matrix with em-bedded hard-magnetic filler particles. In conventional polymer processes, such as pressing or injec-tion molding, these compounds can be processed into magnets with sufficient mechanical strength and stiffness. So far, thermoset-bonded magnets are only processed by pressing which severely restricts the geometrical freedom and the integration of other functions within the process. By fabricating thermoset-bonded magnets via injection molding, complex components and magnetization structures with an increased functional integration could be ena-bled. Furthermore thermoset-bonded magnets allow for higher resistance to temperature and chemical substances compared to thermoplastic-bonded magnets due to lower viscosity.The aim of this project is the systematic investigation of the functional relationship of material com-position, process influences and component geometry as well as gating system on the filler orientation and thus, on the magnetic properties of multipolar thermoset-bonded magnets. This process enables the production of magnets with a defined structure of magnetization, complex and thin-walled geometry and, at the same time, high power density by using the possibilities of the injection molding process. In contrast to thermoplastic matrix systems, thermoset systems achieve their lowest viscosity only after the injection into the cavity, so that significant advantages can be expected with respect to filler orientation. In this case, the orientation of the particles takes place at the moment at which the lowest resistance forces (low viscosity in the cavity) are present, enabling a precise representation of the magnetic field especially directly at the tool contact surfaces, as is required, for example in highly accurate sensor systems. In particular, this improved filler orientation would be advantageous for components with a small pole width and high demands for accuracy of the pole width, but also for components with requirements for a high peak flux density. Furthermore, the application possibilities of polymer-bonded magnets in pump systems and highly accurate sensor systems shall be expanded due to high temperature and media resistance of thermoset systems. Thermoplastic-bonded magnets hardly offer this resistance effect, and only when applying PPS as matrix material. Within the scope of this project, final guidelines for the compound composition, as well as for the processing and design of thermoset-bonded permanent magnets are to be derived. Additionally, influencing variables on the orientability of the hard-magnetic filler particles shall be examined by systematically varying the compound composition, process parameters and component geometry, taking into account the time and curing behaviour of thermoset systems.

• DFG Programme: Research Grants
• Major Instrumentation: Spritzgießwerkzeug
• Instrumentation Group: 2100 Gießanlagen (Spritzguß, Strangguß)