Development of Multifunctional PEEK Nanocomposites based on Graphene

Abstract

In this communication we present the preparation of multifunctional Polyether ether ketone (PEEK) nanocomposites with graphene. PEEK is an important high-perfomance semicrystalline thermoplastic matrix that displays a unique combination of toughness, stiffness, chemical and solvent resistance, retention of physical properties at high temperatures and recyclability. A relevant step forward to expand its field of application is the incorporation of electrical conductivity, developing multifunctional materials. Therefore, graphene has been incorporated into the matrix aiming to achieve electrical conductivity without a significant detriment on PEEK properties. The accomplishment of an effective transfer of the properties from graphene to the matrix is controlled by the nanofiller dispersion within the matrix and the presence of a strong polymer/graphene interface. One of the most efficient strategies to improve both parameters consists on the covalent modification of graphene with short polymer chains and their subsequent use as filler in the cognate polymer matrix1-3. Nevertheless, this approach is unachievable in our case since PEEK is insoluble in organic solvents. An alternative strategy, proven to be effective to increase carbon nanotubes dispersion within PEEK matrix4-5, consists on nanofiller wrapping in compatibilizing polymers. In this study we prepared PEEK/graphene nanocomposites using compatibilizers like polyetherimide (PEI), poly(1-4-phenylene ether-ether sulfone) (PEES), polysulfone (PSU) and sulfonated PEEK (SPEEK), which are amorphous thermoplastic polymers miscible with and structurally similar to PEEK. Composites incorporating compatibilizer/graphene nanofillers display a slight decrease on the thermal stability with respect to PEEK, which is related to the intrinsic thermal stability of the compatibilizer employed. Regarding the electrical conductivity, significant conductivity values were measured depending on both nanofiller concentration and the nature of the compatibilizer. A slight enhancement was observed on the mechanical properties of the nanocomposites for some of the non-covalent functionalized graphene. The morphology, thermal behavior and mechanical performance of all nanocomposites will be compared and the best strategy leading to a balance among electrical, thermal and mechanical properties will be shown.