Synthesis, mechanical properties and chemical/solvent
resistance of crosslinked poly(aryl-ether-ether-ketones) at high temperatures
by Michael E. Yurchenko , Jijun Huang, Agathe Robisson, Gareth H.
McKinley, Paula T. Hammond
A synthetic two-stage procedure was developed for
the synthesis of moderately crosslinked polymers
based on poly(aryl-ether–ether–ketone) (PEEK). Rigid crosslinks based on aromatic imines were synthetically
introduced into PEEK polymer matrix resulting in PEEK materials with various
degrees of crosslinking. Two specific crosslinked PEEK polymers (5% and 10% of ketone groups crosslinked)
were characterized and studied in detail. Thermomechanical
properties, as well as chemical/solvent resistance of these materials at high
temperatures (175–280 °C) were investigated and compared to the original
PEEK material (Victrex 151G). The introduction of
rigid crosslinks was shown to disrupt crystallinity of PEEK very efficiently. Because tensile
properties of PEEK depend on its crystallinity, we
observed a decrease in properties such as Young's modulus and the ultimate
elongation, the extent of which depended on the degree of crosslinking.
We also observed an improvement in the elastomeric properties of the crosslinked materials, such as decrease in initial
permanent set during high temperature cyclic tensile testing. Mechanical creep
behavior at high temperature also improved for crosslinked
polymers vs the original commercial Victrex 151G in terms of a reduced irreversible creep
component. All crosslinked materials showed excellent
resistance to hot oily, acidic and basic environments, as well as excellent
thermal stability. Overall, we were able to synthesize “softer” materials that
are more rubbery at high temperature than commercial thermoplastic Victrex 151G; these elastomer-like
materials showed promising mechanical properties for high temperature
applications in hot/corrosive environments.