Study on modified polypropylene membrane induced by UV-irradiation grafting

A new kind of hydrophilic membrane was prepared through grafting polymerization of acrylic acid (AA) and methacrylic acid (MAA) onto the surface of polypropylene (PP) membrane initiated by ultraviolet (UV), using benzophenone as photosensitizer. The factors influenceing the grafting degree were discussed, such as the concentration of photosensitizer, irradiation time and solvent type. Attenuated total reflection-fourier transform infrared spectroscopy (ATR-FT-IR) and scanning electron microscopy (SEM) were used to characterize the chemical and morphological changes of the original and grafted PP membrane, the results indicated that acrylic acid was grafted onto the surface of PP membrane. Static contact angle measurements and water absorption ratio were used to characterize the hydrophilic changes of the polypropylene membrane surface. In addition, the grafting degree of AA was commonly higher than MAA under the same grafting conditions, furthermore, the grafting degree of AA in water was obviously higher than that in organic solvent. The contact angle of grafted PP membrane decreased from 95° to 35° over a critical grafting degree of 11.8%, the hydrophilic of PP membranes improved dramatically.