Hydrophobisation of electrospun nanofiber membranes by plasma deposited CF coating

Abstract Electrospun nanofiber membranes for filtration and medical applications are still under rapid development. The common example of membranes - polyamide 6 (PA6) with hydrophilic properties was selected for the conversion to hydrophobic membranes. The fiber diameter in the membrane is about 100 nm. To reach the hydrophobic properties, the hydrophilic PA6 membrane was plasma coated by CF film from Argon/C4F8 = 2:1 gas mixture in radio frequency (RF) 20 W plasma in total pressure about 0.7 Pa for 5 min. The membranes are by this process coated deeply inside the structure up to underlying spunbond substrate used for the membrane production as a collector substrate. The contact angle measured on CF functionalized membrane is about 120° and it is higher than the contact angle measured on the reference flat CF coating on Si sample with same chemical bonding. Chemical structure was studied by XPS where identical CFx components were identified on flat samples and on the top of functionalized membrane. The zeta potential decreased significantly if PA6 membrane is functionalized by CF groups. The coating process did not damage the nanofibers in the membrane and the diameters of the fibers were not significantly increased.