Abstract
Polymer bonded permanent magnets find significant applications in a multitude of electrical and electronic devices. In this study, magnetic particle-loaded epoxy resin formulations were developed for in-situ polymerization and material jetting based additive manufacturing processes. Fundamental material and process issues like particle settling at room temperature and elevated temperature curing, rheology control and geometric stability of the magnetic polymer during the thermal curing process are addressed. Control of particle settling, modifications in rheological behavior and geometric stability were accomplished using an additive that enabled the modification of the formulation behavior at different process conditions. The magnetic particle size and additive loading were found to influence the rheological properties significantly. The synergistic effect of the additive enabled the developing of composites with engineered magnetic filler loading. Morphological characterization using scanning electron microscopy revealed a homogenous particle distribution in composites. It was observed that the influence of temperature was profound on the coercive field and remanent magnetization of the magnetic composites. The characterization of magnetic polymers and composites using rheometry, scanning electron microscopy, X-ray diffraction and superconducting quantum interference device (SQUID) magnetometry analysis enabled the correlating of the behavior observed in different stages of the manufacturing processes. Furthermore, this fundamental research facilitates a pathway to construct robust materials and processes to develop magnetic composites with engineered properties.
Highlights
Permanent magnets are used in a wide range of consumer and industrial applications that involve the conversion of mechanical energy to electrical energy, and vice versa
All the magnetic paste formulations experienced reductions in viscosity with an increase in temperature, yet the formulation modified with the highest amount of rheological additive resulted in a viscosity for low shear rates at the epoxy curing temperature that was over 500 times greater in magnitude compared to the comparable paste without additive
The ability of the material to maintain high viscosity at low shear rates at curing temperatures enabled the control of particle settling, which was validated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses
Summary
Permanent magnets are used in a wide range of consumer and industrial applications that involve the conversion of mechanical energy to electrical energy, and vice versa. Permanent magnets find applications in areas like factory automation, medical devices, household appliances, consumer electronics and automotive systems. Permanent magnets are utilized in electro-mechanical devices such as microwave generators, motors, dynamos, actuators, speakers and magnetic couplings [1,2]. A permanent magnet where the magnetic powder is mixed with a polymeric binder is called a bonded magnet. Utilized magnetic powders include the aforementioned magnetic materials and hybrid mixtures thereof. The properties of the polymer bonded magnets depend on the type of magnetic filler used, the polymer binder and the distribution of the filler [4]
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