Polyamide-imide

Polyamide-imides are either thermosetting or thermoplastic, amorphous polymers that have exceptional mechanical, thermal and chemical resistant properties.

[citation needed] Polyamide-imide polymers can be processed into a wide variety of forms, from injection or compression molded parts and ingots, to coatings, films, fibers and adhesives.

The earliest route to polyamide-imides is the condensation of an aromatic diamine, such as methylene dianiline (MDA) and trimellitic acid chloride (TMAC).

In the commercial preparation of polyamideimides, the polymerization is carried out in a dipolar, aprotic solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAC), dimethylformamide (DMF), or dimethylsulfoxide (DMSO) at temperatures between 20–60 °C.

Further thermal treatment of the polyamideimide polymer increases molecular weight and causes the amic acid groups to form imides with the evolution of water.

The magnet wire enamel is made by dissolving the PAI powder in a strong, aprotic solvent such as N-methyl pyrrolidone.

Diluents and other additives can be added to provide the correct viscosity for application to the copper or aluminum conductor.

Application is typically done by drawing the conductor through a bath of enamel and then through a die to control coating thickness.

During this treatment, commonly referred to a postcure, the molecular weight increases through chain extension and the polymer gets much stronger and more chemically resistant.

Before processing the resin, drying is required to avoid brittle parts, foaming, and other molding problems.

The high temperature and chemical resistance of polyamide-imides make them in principle suitable for membrane based gas separations.

Although not currently used in any major industrial separation, polyamide-imides could be used for these types of processes where chemical and mechanical stability are required.