Preparation of the hydrophilic coating layer on polypropylene microporous membrane surface by dip-coating the hydrophilic agent

Polypropylene microporous membranes (PPMMs) have a broad range of applications owing to their outstanding performances and low cost. However, PPMMs are highly hydrophobic and the water permeability is terrible, which enormously obstructs the applications of PP membrane in water treatment. In this work, PPMMs are modified by a chemical crosslinking method, and a crosslinked hydrophilic coating layer is formed on the membrane surface, which greatly improves the hydrophilicity and permeability of the PP membrane. The water flux of the modified membranes is about 350 L·m⁻²·h⁻¹ (the pressure of 0.2 MPa). The water contact angles are reduced to about 10°, and compared to unmodified membranes, it is reduced by 90°. Meanwhile, the flux repeatability experiment of the modified membrane proves that the crosslinking agent improves the stability of the membrane. X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectrometer are employed for the characterization of chemical properties and morphological variances of original and modified membrane surfaces. The results exhibit that the groups such as C–O, O=C–O, and O–C–O are introduced successfully to the PP membrane surface.