Polyetherimide (PEI) - PEI is considered an advanced thermoplastic which has both ether links and imide groups in its polymer chain. Polyether imide has gained rapid acceptance as a high temperature engineering thermoplastic material competitive with the polysulfones, polyphenylene sulfides, and polyketones. Polyether imide exhibits high tensile strength without the use of reinforcement, flame resistance, very low smoke emission, and excellent hydrolytic stability. Because of PEIs high stability, its range of processing is wider than many other thermoplastics.

In 1982 General Electric introduced the first polyetherimide (PEI) under the trade name Ultem. They discovered that the presence of the ether linkages was sufficient to allow the material to be melt processible, while retaining many of the key characteristics of polyimides.