Other Thermoplastic Polyetherimides

BPADA has been polymerized with a wide variety of other diamines and other dianhydrides to produce a family of polymers and copolymers. Chief among these is the polymer of BPADA with p-phenylene diamine (PPD), as shown in Eq. (8.6). This PPD resin has a slightly higher T than the MPD resin and also has much better solvent resistance. Removal of the MPD-derived kink from the PEI chain makes the resin much less soluble, but symmetry is not so high as to allow for crystallization under most conditions. The presence of the three flexible links—two ether groups and an isopropylidene linkage—still allows for melt processability. The Tg is raised slightly to 227°C (441°F), and solvent resistance is much improved versus the BPADA-MPD polymer. 

Copolymers of BPADA with PMDA and MPD have been made to jdeld a higher Tg. By incorporating a minor amount of PMDA, as used in Kapton polyimide, the Tg is raised to 234 C (453 F) with a slight reduction in flow due to incorporation of the inflexible PMDA linkage in the polymer backbone [Eq. (8.7)]. Other properties are retained. 

A partial summary of commercial polyetherimide grade names and their suppliers is listed in Table 8.1. Table 8.2 shows properties of some of the commercial, fully amorphous, melt-processable thermoplastic polyimides listed in Table 8.1. They have high heat capabflity and excellent strength [23]. 

TABLE 8.1 Commercially Available PEI Resins and Their Trade Names 

Chemical name in this chapter Commercial trade name Grade Manufacturer 

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The authors suggest, based on this information, that a class of low temperature alloys such as In-Pb, Sn-Zn, Pb-Sn-Ag, Sn-Pb, Sn-Pb-Sb, Sn-Ag, Bi-Pb-Sn-Sb could be used as shielding materials. Other thermoplastics such as polyimide, polyetherimide, polyamideimide, polyphenylene sulfite, and PEEK are possible matrices as well. Recently a product which is a thermoformable EMI-shielding material has been introduced. It is made of solder-like low melting temperature bismuth-tin alloy and a non-woven EVA polymer. At 1 GHz its shielding effectiveness is claimed to be greater than 40 dB [3]. 

Connectors, switches, electric distributors, fuse boxes and other electric fittings need a subtle balance of electrical and mechanical properties, durability, cost and aesthetics. This broad field creates fierce competition not only between engineering thermoplastics and SMC/BMC for the main applications but also with polypropylene and polyethylene or PVC for the lower performance parts and, at the opposite end of the scale, with high-tech plastics such as polyetherketone, polyetherimide, liquid crystal polymers. .. For example, without claiming to be exhaustive ... 

In the electronics industry, one of the most successfiil uses of advanced composites has been in PCBs. General Electric s Ultem polyetherimide is used in transport PCBs, especially aerospace an missile guidance systems. Polysufibnes and other high-performance thermoplastics are being used in multilayer PCBs for mainframes and supercomputers operating at gigahertz frequencies. 

Other engineering thermoplastics have also been examined and found to be effective e.g., polyetherimide [121-124], poly(ether ketones) (PEK) [125,126], poly(phenylene oxide) [127-129], and liquid crystalline polymers [130, 131]. 

Wilson et al. [3] showed that pultrusion is also applicable to other high-performance thermoplastics, in particular, amorphous polyetherimide (PEI). In this case, a wet-impregnation station for impregnating carbon fiber bundles with a PEI solution was put in line with a die system that was designed to consolidate multiple plies of prepreg tape by gradual reduction into rectangular profiles. 

Besides the thermoplastic elastomers based on poly(styrene-6-elastomer- -styrene) block copolymers, five others are of commercial importance polyurethane/elastomer block copolymers, polyester/elastomer block copolymers, polyamide/elastomer block copolymers, polyolefin block copolymers, and polyetherimide/polysiloxane block copolymers. All five have the multiblock A-B-A-B. structure. The morphology of the polyurethane, polyester,... 

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