Continuous dip coating of PVDF hollow fiber membranes with PVA for humidification

Influence of surface properties on the dip coating behavior of hollow fiber membranes

“…PES and PVDF membranes were made via nonsolvent‐induced phase separation. The fabrication process and the geometric characterization method have already been described elsewhere . Four different membranes were made, details of the compositions of the dope solution and coagulants are shown in Table .…”

“…For dip coating the coating device represented in Jesswein et al was used. Briefly, hollow fibers were continuously drawn through a dip coating solution and dried directly afterwards.…”

“…The post‐treatment of membranes by a coating is done for several fields of applications. On porous hollow fiber membranes dense layers of highly selective polymers are applied for gas or vapor separation as well as to manufacture membrane contactors or reactors . Furthermore, dip coating of hollow fiber membranes is also used to tune special membrane properties.…”

“…In a batch process, fibers or even complete modules are sealed at the ends and are dipped into the coating solution. For continuous fiber coatings the fibers run over a roll, which is installed in the dip coating bath . Other publications use a glass coater as a coating device with two open ends on the opposite sides where the fibers run through .…”

“…Coating layer thicknesses and transition layers, where intrusion took place, were analyzed by Doppler broadening energy spectra using positron annihilation spectroscopy. In a previous work of ourselves, the thickness of dense layers on a membrane was determined by weighing before and after coating …”