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

聚合物粘结永磁体是由聚合物基体和嵌入的硬磁填料颗粒组成的复合材料。在传统的聚合物工艺中，例如压制或注射成型，这些化合物可以加工成具有足够机械强度和刚度的磁体。到目前为止，热固性粘结磁体仅通过压制来加工，这严重限制了工艺中的几何自由度和其他功能的集成。通过注射成型制造热固性粘结磁体，可以实现具有增加的功能集成度的复杂部件和磁化结构。此外，由于粘度较低，与热塑性粘结磁体相比，热固性粘结磁体具有更高的耐温性和耐化学物质性。本项目的目的是系统地研究材料成分、工艺影响和组件几何形状以及浇注系统对填充物取向的功能关系，从而影响多极热固性粘结磁体的磁性能。该工艺能够通过使用注塑工艺的可能性来生产具有限定的磁化结构、复杂的薄壁几何形状以及同时高功率密度的磁体。与热塑性基体体系相比，热固性体系仅在注入型腔后才达到其最低粘度，因此在填料取向方面可以预期显著的优点。在这种情况下，颗粒的定向发生在存在最低阻力（空腔中的低粘度）的时刻，从而能够精确地表示磁场，特别是直接在工具接触表面处，这是例如在高精度传感器系统中所需要的。特别地，这种改进的填料取向对于具有小极宽和对极宽的精度的高要求的部件是有利的，而且对于具有对高峰通量密度的要求的部件也是有利的。此外，聚合物粘结磁体在泵系统和高精度传感器系统中的应用可能性将由于热固性系统的高温和耐介质性而扩大。热塑性粘结磁体几乎不提供这种电阻效应，并且仅当应用PPS作为基体材料时。在这个项目的范围内，化合物的成分，以及热固性粘结永磁体的加工和设计的最终准则是派生。此外，应通过系统地改变化合物成分、工艺参数和组件几何形状，并考虑热固性系统的时间和固化行为，检查影响硬磁填料颗粒定向性的变量。

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.