Thermoanalytical investigation of the role of the solvents in the preparation of polyimide films

Polyamido acid (PAA) synthesized from pyramellitic dianhydride and diaminodiphenyl-ether has been subjected to thermal analysis by a coupled simultaneous technique (TG, DTG, DTA, TVA). It was established that amide solvents—dimethyl formamide, dimethyl acetamide and N-methyl pyrrolidone—profoundly affect the process of transformation of PAA into polyimide (PI) and thermal characteristics of the latter. It was found that the thermal stability of PI depends on conditions of the preparation of PAA films (drying time and film thickness) and on the boiling point of the solvent. The necessity for a combined approach to the evaluation of thermal stability of PI is shown.