Mechanical properties of injection molded NdFeB permanent magnets

Summary form only given. Recent developments in the injection molding of PPS (polyphenylenesulfide) containing NdFeB magnetic powders has enabled the high-volume, cost-effective production of high performance magnets for energy-efficient motors and actuators in automotive applications. This study investigates the mechanical properties of these magnets according to ASTM standards D638-99 and D790-99. Samples with different volume concentrations of NdFeB powders were evaluated at temperatures between -40C and 180C, which cover the range of temperatures expected in automotive applications. At each temperature, four samples were tested and the average of these four data sets were used to represent the properties of the injection molded magnetic material. Test results show significant differences in tensile strength at cryogenic, room, and operating temperatures. The tensile strength ranges from 60 to 80 MPa at 22 and -44C and drops to below 23 MPa at 100 and 180C. Scanning Electron Microscopy was used to examine the fracture surfaces and gain insights on the failure mechanisms. The results of this study can be used for material selection by motor and actuator designs and for further improvement of the injection molding process. Tensile stress-strain curves for PPS injection molded samples with different volume concentration of NdFeB at four temperatures are shown and reveal the increasing compliance of the material with test temperature. SEM pictures of the fracture surface of samples tested at -40 and 180C show the effect of temperature on the fracture pattern of the PPS bond.