Abstract: A method of preparing polyimide foam produces a foam with excellent flexibility properties. The method of preparing polyimide foam is performed by foaming polyimide percursor which is prepared by employing linear aliphatic diamine and aromatic diamine containing 4 to 12 carbon atoms, at specific weight ration into the esterified reaction mixture prepared by reacting an aromatic carboxylic acid or its anhydride with excess amount of an alcohol compound. The polyimide foam produced by the method described retins superior characteristics of conventional polyimide foams and in addition have excellent flexibility so that it is used widely as adiabatic material, acoustical absorbent and cushion material in the aerospace industry, submarine and express trains etc.

Abstract: This invention relates to melt processable copolymer of etherimideimide/etherimide herein-after identified as PEII/PEI copolymer of following structural formula(I). ##STR1## wherein, R and R' are independently selected from the groups of ##STR2## Ar and Ar' are independently selected from the groups of ##STR3## (wherein, R1 is H or C1-C6 alkyl group,R2 is II or C1-C4 alkyl group, andR3 is --O--, --CO--, --SO--, --SO2--.); andn and m are independently an integer between 5 and 500.