STRUCTURE AND PROPERTIES OF NEW POLYIMIDE BONDED MAGNETS WITH ENHANCED BENEFITS

摘要

We report a new method for preparing thermally-stable and processable polyimide (PI)-bonded magnets via the chemical transformation of PI prepolymers (based on diacetyl derivatives of diamines and dianhydrides) filled with magnetic Nd-Fe-B alloy particles (75-100 μm). The prepolymers with amorphous structure, after removing of up to 5% volatile, can be melted at 220+-10°C to give a fluid with a very low viscosity of 15+-5 Pa·s. This low viscosity of the prepolymer facilitates blending it with the magnetic particles at relatively high volume fractions up to 85 vol.%. The resulting Pi-bonded magnets were found to exhibit excellent thermal stability, high storage modulus of 10 GPa at 400°C; and a 10% increase in energy product over that of commercially available bonded magnet materials.