PEEK also exhibits good chemical resistance in many environments, including alkalis (i.e. sodium, potassium and ammonium hydroxides), aromatic hydrocarbons, alcohols (i.e. ethanol, propanol), greases, oils and halegonated hydrocarbons.
However, it's performance in acids is very dependent on the type of acid - PEEK shows poor resistance in oleum and concentrated sulphiric, nitric, hydrochloric, hydrobromic and other mineral acids (though performance may be adequate for short term use with these acids in very dilute form). It's resistance to hydrofluoric acid and oleum is very poor. PEEK shows good resistance to phosphoric acid and organic acids (acetic, citric, oxalic, tataric etc.), but varying resistance in the presence of halogens. PEEK is resistant to dissolution by some formaldehydes and ketones such as acetone, but not (at higher temperature) methylethyl ketone.
