Introduction

In the case of polyimides, aromatic polyimides polymerized from aromatic monomers which were insoluble and infusible had always been present. Of all the polyimides, nonthermoplastic polyimides polymerized from pyromellitic dianhydride (PMDA) and bis(4-aminophenyl)ether (ODA) have a long history of roughly 40 years since commercialization under DuPont. The polyimide cannot be melted or injection-molded and therefore has some limitations for complicated design and productivity. In the late 1980s, Mitsui Chemicals, Inc. ^[1] began investigating and developing a thermoplastic polyimide to meet industry needs. As a result of these efforts, a super engineering plastic called Aurum was launched. This material is synthesized from pyromellitic dianhydride and 4 ?-bis (3-aminophenoxy)biphenyl and has a high heat resistance with glass transition temperature T _g = 482 F (250 C). Aurum is an injection-moldable semicrystalline polyimide, but it has a very slow crystallization rate. The part obtained through injection molding is amorphous, not crystalline, although Aurum is a semicrystalline polymer. The postcuring after injection molding enabled crystallization, but control of the tight dimension was not sufficient. In the early 2000s, another new thermoplastic polyimide entered the market, called SuperAurum, an in-mold crystallizable polyimide, which has an excellent HDT of 752 F (400 C) with carbon fiber filler. It is in a crystalline state during injection molding, because of the enhancement of the crystallization rate. SuperAurum has better chemical and mechanical properties. The polymer was completed through...