Title

Polyimide Bonded Magnets: Processing and Properties

Document Type

Article

Publication Date

6-28-2003

Department

Polymers and High Performance Materials

Abstract

We report a new method of polyimide synthesis based on the interaction of dianhydrides with acylated diamines; for preparing a melt processable mixture of prepolymer and rare earth magnetic alloy particles in the form of 75-100 mum particles. This mixture can be easily converted to useful thermoplastic polyimide bonded magnets by heating at 300degreesC. It is shown that the prepolymer based on 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride and the diacetyl derivative of 2,2-bis(4-(4-aminophenoxy)phenyl)sulfone diamine after removing less than 5% by weight of the volatile components can be melted at 220-240degreesC to give a fluid with a viscosity of 10-20 Pas. This low viscosity of the prepolymer facilitates blending it with magnetic particles at relatively high volume fractions (up to 85 vol %) that are not possible using conventional methods. The resulting polyimide-bonded magnets exhibit excellent thermal stability and a high storage modulus of 10 GPa at 400degreesC. Magnetic property measurements showed a greater than or equal to10% increase in energy products over that of typical commercial bonded magnet materials such as the ones containing thermoplastic poly(phenylene sulfide) or polyamide matrices. (C) 2003 Wiley Periodicals, Inc.

Publication Title

Journal of Applied Polymer Science

Volume

88

Issue

14

First Page

3151

Last Page

3158