TRANSPORT-PROPERTIES OF CROSS-LINKABLE POLYIMIDE BLENDS

The use of polymeric membranes for separation of chemically aggressive media, or at elevated temperatures, has been limited by membrane avai lability. While a number of polymers are both resistant to chemical di ssolution and thermally stable to over 300 degrees C, none has been sh own to be simultaneously capable of the selective transport of gases a t high rates. The research reported here analyzes the influence of sol id-state crosslinking of polyimides to achieve this unique combination of properties. Polyimide blends consisting of an inert polymer base w ith a diacetylene-functionalized additive were prepared and the proper ties evaluated before and after crosslinking by thermal annealing. Cro sslinking rendered the resultant polymers insoluble in what were previ ously solvents, but had no measurable influence on gas permeabilities or selectivities. The permeability/permselectivity of these new crossl inked polyimide bleeds are competitive with the best known polymers. M oreover, the combined ease of processing and resultant stability are u nmatched.