Ionic Liquids as a New Platform for Fiber Brittleness Removal

In the present study, three ionic liquids, 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), 1-allyl-3-methylimidazolium ([AMIM]Cl), and 1-ethyl-3-methylimidazolium chloride dimethyphosphate ([EMIM]DMP), were used to eliminate the brittleness of recycled fibers. The results showed that the pretreatments with ionic liquids were able to modify and improve the properties of recycled fibers even at high moisture contents. [EMIM]DMP gave better performance compared to [BMIM]Cl and [AMIM]Cl, which can tolerate higher moisture contents. The optimal conditions of EMIM]DMP pretreatment were moisture content of 65%, [EMIM]DMP dosage of 20 wt-%, 80 °C, and 60 min, for which a higher brittleness removal was obtained. The tensile index, bursting index, and tearing index of handsheets were increased by 32.4%, 57.0%, and 46.5%, respectively. Fiber quality was improved as demonstrated by fiber length, lowered fines content, and increased swellability. Such results imply that ionic liquids pretreatment can promote the swelling of recycled fibers and remove their brittleness.