Polyimide And Related Polymers

Among the heat-resistant resins, polypyromellitic acid diimide (Ⅳ) produced by DuPont company is a representative resin with excellent performance and a wide range of uses. In this company, in addition to fibers (trial products), there are also varieties in various forms such as films (Kapton), molded products (Vespel), insulating paints for electric wires (Pyre ML) and glass fiber reinforced laminates (Pyralin), which have been successfully commercialized.

It is well known that polyimide is made from tetracarboxylic dianhydride such as pyromellitic dianhydride and aromatic diamine through two steps (ring opening plus polymerization and cyclization condensation). In the composition of polyimide, pyromellitic dianhydride and other tetracarboxylic acids are used as tetracarboxylic acid components. For example, from the perspective of insulating paint used for wires, the previous wire manufacturing technology used cresol soluble varnish with convenient operation and favorable cost, but now the following commercially available polyimides are used.

In DuPont, in addition to the above polyimide products, another polyimide NR-150 with improved formability has been put into production. Since these polyimides are soluble in solvents such as dimethylformamide and NMP, they can be used as adhesives for lamination to obtain a heat-resistant laminate (graphite fiber as a reinforcing material) having excellent mechanical properties and substantially no air bubbles. It is expected that polyimide can be used as a general basic material. Polyamide monoimide (Ⅷ) is prepared from trimellitic anhydride acyl chloride and diamine by two-step method or trimellitic anhydride and diisocyanate by one-step method.

In terms of good heat resistance, polyimide is also poor, but it is easy to use, has excellent processability and mechanical properties, so it has been successful. This type and the modified type have been sold in many companies, mainly used as electrical insulating materials such as insulating paint, varnish and film for wires.

This kind of polyamide monoimide resin can be molded if some improvements are made to the normal injection molding machine (Torlon of Amco). The performance of this molded product is different from that of polyimide molded products: tensile, bending and compressive strength are relatively large, and it can be used continuously at 280 ℃, which is one of the biggest characteristics.

The main use of these molded products is expected to be used to manufacture gear, pump components, valves, bearings and other mechanical parts. Polyimide Vespel is formed by a special compression sintering method of powder metallurgy type, which can only obtain a simple round bar shape (it can replace precision mechanical parts that need to be cut twice). The polyamide imide molded products formed by this injection molding have great potential for future development in terms of performance and price.

There are several non typical polyimides, which can be cured by heating (including its oligomer), and have been applied. In the molding of oligomers, heat-resistant products (laminates, molded products, etc.) that are crosslinked and cured and do not generate air bubbles are particularly useful in the molding. A representative example is the preparation of polyamine monoimide (IX) (Kinel and Kerimid of LonePoli) from bismaleimide and diamine via NIichael type addition polymerization.

This resin can be used to prepare solvent based varnish (NMP solvent) with high molecular weight polymer or solvent free varnish with oligomer mixture. Curing occurs due to heating, which is achieved by heating polymerization of maleimide double bonds existing in the terminal group. There are many reports on the Michael type addition polymerization of diamines and their derivatives, dithiol, dialdehyde oxime, diimide, disulfonic acid, etc. with bismaleimide to produce various polyimide derivatives.

Polyimide oligomers with functional groups that may be polymerized introduced into the end groups include the product with 5-norbornenyl 2,3-dicarboxyimide at the end (x, p13n from Ciba Jiaji) [22] and the product with acetylene group at the end (Xi, hr-600 from Gulf oil company), which have been commercialized.