Mechanical properties of polyphenylene-sulfide (PPS) bonded Nd–Fe–B permanent magnets

Mechanical properties, namely tensile and flexural strengths and elastic modulus, of polyphenylene-sulfide (PPS) bonded Nd–Fe–B magnets have been studied from −40 to 180 °C. The ultimate tensile strength (Sut) of PPS bonded magnets decreases with increasing temperature. The tensile strength of PPS bonded Nd–Fe–B magnets was reduced significantly above 100 °C. At 180 °C, the PPS bonded magnets still exhibit a Sut of 16–18 MPa. For bonded magnets with about 60% volume fraction of Nd–Fe–B powder, the PPS bonded magnet shows about twice the tensile strength and half the ultimate strain compared to that of Nylon bonded magnet. At room temperature, the flexural strength is, in general, comparable to the tensile strength. Dynamic elastic modulus measured using the impact resonance method was in good agreement with the elastic modulus obtained from tensile tests. Scanning Electron Microscopy analyses of the fractured surfaces revealed two distinct failure mechanisms. Debonding along the Nd–Fe–B particle and PPS interface is the main cause for failures at 100 and 180 °C. The fracture of Nd–Fe–B particle was observed on the fracture surface of specimens tested at −40 and 23 °C.