Novel processable aromatic thermoplastic polyimides: Films,adhesives, moldings,and graphite composites

Novel hot-melt type flexible, tough, thermally stable, processable, thermoplastic, aromatic polyimides have been synthesized involving reaction of a keto-ether containing diamine with hinged aromatic dianhydrides followed by thermal and chemical cyclodehydration. Inherent viscosity in DMAC at 35°C of the synthesized polymers ranged 1.02 to 1.4 dl/g (0.5% solution). The polymers showed a glass transition temperature (T_g) of 250°C to 180°C as determined by differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). Thermogravimetric analysis showed polymer stability up to 510°C, in both air and nitrogen atmospheres. All the polymers have shown good melt-flow. Films of 1.5–2.8 ml thickness were made and tested for mechanical properties at room temperature, 177°C and 210°C. The developed films are suitable for adhesion of Ti/Ti specimens and showed a lap shear strength of 5575 psi. Melt-fusion of the polymers gave tough moldings. Graphite cloth composites have been made and tested for mechanical properties.