Design and characterization of polymers and polymer blends for high temperature structural applications

Reviewing the development of new polymeric materials for high temperature structural applications (T > 200°C) over the past several decades, reveals a paradox which, to date, has not been completely resolved. Polymers which exhibit very high temperature stability tend to be either intractable or brittle, whereas, easily processible polymers tend to fall short of property targets. Approaches to resolving this paradox include modification of the chain backbone chemistry and polymer blending (especially to form miscible systems). Recent research has shown that, in contrast to low temperature flexible polymers, many high temperature aromatic heterocyclic polymers form miscible systems which permit the design of the desired processibility and performance into the blend. An example of such a system is the blend of Poly(2,2′‐(meta‐phenylene‐5,5′‐bibenzimidazole) (PBI) with a series of polyamides, including commercially available polyether imide (PEI) and imide copolymers containing sulfone and fluorinated isopropylidene (6F) units. Other examples include all polyimide blends and blends of polyimides with polyethersulfone.