Depolymerization of ODPA/ODA Polyimide in a Fused Silica Capillary Reactor and Batch Autoclave Reactor from 320 to 350 °C in Hot Compressed Water

Depolymerization of polyimide synthesized from 4,4′-oxidiphthalic anhydride and 4,4′-diaminodiphenyl ether monomers (ODPA/ODA PI) in hot compressed water was carried out in a fused silica capillary reactor (FSCR) and batch autoclave reactor system. The phase behavior of ODPA/ODA PI in water during the heating, reaction, and cooling stages of the process in FSCR was observed with an image recording system from under the microscope. The effects of temperature (320–350 °C) and reaction time (30–90 min) on the depolymerization yield and products yields in batch autoclave reactor were investigated at a fixed H2O/PI ratio, and optimal conditions were established. Additionally, an understanding of the reaction pathway of ODPA/ODA PI depolymerization in hot compressed water was developed.