Thermo-processable polyimides with high thermo-oxidative stability as derived from oxydiphthalic anhydride and bisphenol A type dianhydride

Two series of homopolyimides based on oxydiphthalic anhydride and bisphenol A bisether-4-diphthalic anhydride were synthesized with 12 kinds of aromat ic diamines. Several thermo-processable homopolyimides were the focus of fu rther investigation. The structure-property relationships of these homopoly imides were examined as functions of the glass transition temperature (T-g) , melting point (T-m), thermal decomposition temperature (T-d), and melt-fl owability. The effects of the chemical and higher-order structures on these properties were discussed in this work to obtain an indication for the mol ecular design of high-performance thermoprocessable polyimides. A series of thermoplastic copolyimides were prepared to achieve higher T-g and T-d wit hout sacrificing thermo-processability. The copolyimides investigated exhib ited a comparable or lower melt viscosity, higher T-g and T-d, and higher l ong-term thermo-oxidative stability than those of ULTEM type polyimides. On e of them exhibited a low melt viscosity (4700 poise at 400 degrees C), a h igh T-g (224 degrees C), and excellent thermo-oxidative stability.