Miscibility of three different poly(aryl ether ketones) with a high melting thermoplastic polyimide

Three poly(aryl ether ketone)s (PAEKs) were melt blended at 415°C with a new thermoplastic polyimide (N-TPI) composed of (4,4′bis(3-aminophenoxy) biphenyl) and pyromellitic dianhydride. The PAEKs studied were poly(aryl ether ether ketone) (PEEK), poly(aryl ether ketone ketone) (PEKK) and poly(aryl ether ketone) (PEK). Although chemically similar, these three show distinctly different behaviour when blended. We have concentrated on amorphous blends in this work so the difference in the crystallization rates of the PAEKs is not a factor in our determination of miscibility. It was found that PEEK was immiscible with N-TPI at all proportions. PEKK is the slowest crystallizing polymer and is miscible at most proportions, as evidenced by single glass transitions. PEK is miscible at N-TPI contents of less than ∼ 50% and partially phase separated in the N-TPI rich blends. It is apparent that the higher percentage of ketone linkages in the PAEKs correlates with the higher degree of miscibility. Charge transfer complexation could also be a factor but this has yet to be explored.