Tensile and heat resistance behavior of modified thermoplastic polyurethane elastomer in anisotropic neodymium-iron-born bonded magnet

The emergence of anisotropic neodymium-iron-boron (NdFeB)-bonded magnets with high energy density and freedom of shape design is effective in minimizing the dimensions and mass of electric motors. However, limitations in mechanical strength and heat resistance at elevated temperatures hinder their further application. To overcome these challenges, we present a novel approach to enhance the tensile strength and heat resistance of the NdFeB-bonded magnet involving the modification of thermoplastic polyurethane (TPU) through the melt-mixing method with a styrene-acrylonitrile-glycidyl methacrylate terpolymer (SAG) modifier and engineered TPU was then employed in fabricating NdFeB-bonded magnets via calendering molding. The microstructure of the magnets exhibited aligned NdFeB particles due to mechanical stress during calendering molding, which results in anisotropy. Interestingly, the magnetic properties of bonded magnets based on modified TPU remain almost the same compared to their unmodified counterparts, showcasing a maximum energy product of around 12 MGOe. The mechanical tests demonstrated a maximum 32.4% increase in the tensile strength of bonded magnets based on modified TPU. A progressive shift to a higher temperature (100 to 120 degrees C) of magnet samples fractured occurs in the heat resistance measurement of the bonded magnets based on modified TPU, meaning improvement in heat resistance of NdFeB bonded magnets. The development of modified TPU to improved thermal behaviors and mechanical properties of anisotropic neodymium-iron-born bonded magnet.image