BTDA 3,3 ,4,4 -benzophenonetetracarboxylic acid dianhydride

During the last several years, a thermoplastic condensation polyimide (PI) was developed at NASA Langley Research Center (49). Prom the reaction between BTDA (3,3, 4,4 -benzophenonetetracarboxylic acid dianhydride) and DABP (3,3 -diamino benzophenone), the polyimide LARC-TPI (Pig. 7) was prepared by Bell et al. (49). Later, St. Clair (50) used LARC-TPI as an adhesive for titanium. The adhesion of titanium and PI has been studied by Nightman et al. (51) with XPS (ESCA) and PT-IR techniques. 

The polyamic acid (Fig. 3.7) precursor was prepared by adding stoichiometric amounts of3,3,4,4-benzophenonetetracarboxylic acid dianhydride (BTDA) anddiami-nodiphenylsulfone (DDS). The solution in NMP was then submitted to either thermal or MW activation with accurate monitoring of the temperature (Scheme 3.14). 

A series of 15 wt % isomeric polyimide precursor resin solutions was prepared by the National Aeronautics and Space Administration Langley Research Center. The polymerization procedure has been described previously (2,3). The poly(amic-acid) resin solutions were made from 3,3, 4,4 -benzophenonetetracarboxylic acid dianhydride (BTDA), 4,4 -oxydiphthalic anhydride (ODPA), diaminobenzophenone (DABP), and methylenedianiline (MDA) monomers. 

Reaction polymerization reactions of isocyanates with suitable monomers can he performed in an extruder or in a RIM machine. In the latter reaction thermosets (cross-hnked polymers) are produced. In an extruder usually linear polymers are manufactured. For example from methylene di-p-phenylene isocyanate (MDI), with some macroglycols and 1,4-hutanediol as extenders, segmented polyurethane elastomers are produced in an extruder (6). However, linear condensation polymers are also produced in a vented extruder. For example from MDI, with macrodicarboxylic acids and dicarboxyhc acids as extenders thermoplastic block copolyamide elastomers are produced. The by-product of the condensation reaction, carbon dioxide, is removed in the vented extruder. The polycondensation process can also be performed in solution. For example, MDI can be added to a solution of dicarboxyhc acids in tetramethylene sulfone, with simultaneous removal of the carbon dioxide. Tetramethylene sulfone is the solvent of choice for solution polymerization of isocyanates (7). In addition to dicarboxyhc acids trimellitic acid anhydride and benzophenonetetracarboxylic acid dianhydride (BTDA) are utilized as monomers for condensation polymers. With these monomers poly(amide imides) and poly(imides) are produced. The diisocyanate-derived commercial polycondensation products are listed in Table 1. 

Figure 11 Reaction of 3,3, 4, 4 -benzophenonetetracarboxylic acid dianhydride (BTDA) 18 with 3,3 -carbonylbisbenzeneamine 19 in the presence of dicyclohexylcarbodiimide (DCC) leading to polyisomide (polyiminolactone) 21 via the intermediate polyamic acid 20. Isoimide-imide conversion predominantly occurs by heating polymer 21 at 300°C, followed by a final excursion at 350-400°C.

Materials. 3,3, 4,4 -Benzophenonetetracarboxylic dianhydride (BTDA), 4,4 -methylenedianiline (MDA), p-aminobenzonitrile (PABN), and p-toluenesulfonic acid monohydrate (PTSA) were of commercial sources and used as received. Graphite fiber used as the reinforcing filler was Hercules HMS grade. 

---