Surface wettability of supercritical CO2 - ionic liquid processed aromatic polyamides

Wettability of aromatic polyamides (aramids) was investigated after exposed to the binary system of 1-Butyl-3-methylimidazolium hexafluorophosphate and supercritical CO2, which was performed at a pressure of 30 MPa for 60 min by varying the treatment temperature between 80 degrees C and 120 degrees C. Dynamic contact angle analysis for the original and treated aramids was conducted to determine the correlation between the surface treatment and the polymer wettability. It is confirmed that the water contact angles for aramids were reduced significantly from 139.8 degrees to 83.0 degrees in the supercritical CO2 -ionic liquid systems, and the hydrogen bonding structure between the amide linkages in aramids and the PF6 in [BMIM] [PF6] was proved to form, which is conducive to the improvement of wettability. SEM observations revealed more and more pleat-like wrinkles appeared on the surface of aramid, accompanied by the notable fiber swelling in the supercritical CO2-ionic liquid systems. In addition, XRD and TG analysis indicated that the crystallinity and the maximum decomposition temperatures of aramids were decreased gradually with ionic liquid treatment while those of aramids were increased with the temperature rising by adding ionic liquid in supercritical CO2. Overall, this proves to be an more effective and ecofriendly approach for aramid modification by supercritical CO2-ionic liquid systems.