DDM Curing Enhancement for the Epoxy Resin Binder Bonded Nd–Fe–B Magnets

With the development of bonded Nd-Fe-B magnets, modifying epoxy resin (EP) binder has become a key factor to improve the properties of bonded Nd-Fe-B magnets. In this work, the magnetic properties, compressive strength, and microstructure of the bonded Nd-Fe-B magnets with diaminodiphenylmethane (DDM)-cured EP binder were systematically investigated. The results show that adding 20 wt% DDM to EP monomer maintains excellent magnetic properties while obtaining optimal temperature resistance and high compressive strength for magnets. Because the molecular structure of the DDM curing agent contains rigid groups, it can enhance the heat resistance and mechanical properties of the EP binder. In addition, fracture surface morphology observation reveals the bonding mechanism of DDM-EP bonded magnets and confirms the advantageous nature of DDM-EP binder for bonded magnets.