High-temperature steam-treatment of PBI, PEEK, and PEKK polymers with H2O and D2O: A solid-state NMR study

Polyaryletherketones (PAEK) in blend systems with polybenzimidazoles (PBI) are of commercial interest due to their increased service temperature and reduction in abrasive wear against soft counterfaces when compared to PAEK alone. ASTM standard tensile specimens of PBI, polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) are immersed in stirred D2O at room temperature, and additional samples are contacted with D2O steam at temperatures of 150 and 315 °C. All samples are studied by TGA, IR, 13C CP/MAS, 1H wideline, and 2H MAS NMR. Changes in the physical appearance of the samples and the extent of D2O uptake are described. Different locations, mobilities, and types of water and protons in the polymers are identified and studied and it is proven that PBI contains the largest amounts of D2O after exposure under all conditions. PEEK and PEKK only incorporate minimal amounts of D2O even when steam-treated at 315 °C.