The effect of ionic liquid on the solubility of polyetheretherketone (PEEK)

Abstract

This paper aims to investigate the suitability of ionic liquids to be used as a co-solvent along with a few common solvents which are dimethyl sulfoxide (DMSO), acetonitrile, and water as the primary solvent to dissolve polyetheretherketone (PEEK). PEEK is an excellent colourless polymer with top-notch mechanical properties. Currently, there is no solvent capable of dissolving PEEK. Therefore, with ionic liquids (ILs) promising performance as solvents to various material including polymers which has been stated in previous literature, it is assumed that ILs would behave as an excellent solvent for PEEK. In this study, three different ionic liquids were chosen which are tetramethylammonium chloride (TMACL), tetramethylammonium hexafluorophosphate (TMAHFP), and tetramethylammonium sulphate (TMAS). PEEK was exposed to these solvent mixtures at ambient temperature and 50 °C for one hour. Fourier Transform Infrared (FTIR) spectroscopy was used to determine the functional group present in the samples. Results highlighted that PEEK did dissolve in DMSO/TMACL and DMSO/TMAHFP at ambient temperature. As the temperature increased to 50 °C, PEEK dissolution decreased in both mixtures. However, the opposite was observed for DMSO/TMAS. Finally, it was found that water and acetonitrile were not able to dissolve PEEK even with the addition of ILs.