Surface roughness and hydrophilicity enhancement of polyolefin-based membranes by three kinds of plasma methods

The introduction of antibacterial property, conductivity, wettability and antithrombogenicity into polyolefin-based membranes has evoked much attention, which can be achieved by coating hydrophilic polymers. Therefore, it is necessary to modify the roughness and hydrophilicity of polyolefin-based membranes to enhance the coating ability. In this paper, three kinds of plasma methods, including inductively coupled (ICP) plasma, radio frequency low pressure (RFP) plasma and atmospheric dielectric barrier discharge (DBD) plasma, were used to modify the surface of the polyethylene (PE), polypropylene (PP) and polyester-polypropylene (PET–PP) membranes. The surface roughness of the plasma-modified PE, PP and PET–PP films was investigated by scanning electron microscopy (SEM) and atomic force microscope (AFM). The polar functional groups of films were observed by energy dispersive spectrometer (EDX) and X-ray photoelectron spectroscopy (XPS). Besides, the hydrophilicity of the plasma-modified PE, PP and PET–PP films was evaluated by water contact angle measurement. It was found that the surface roughness and hydrophilicity of plasma-modified PE, PP and PET–PP films increased with the generation of oxygen-containing functional groups (i.e. C―O, and CO). The PET–PP membranes were treated by RFP plasma at different processing powers and times. These results indicated that plasma is an effective way to modify films, and the treatment time and power of plasma had a certain accumulation effect on the membranes' hydrophilicity. As for the roughness and hydrophilicity, the DBD plasma modifies the PE film, which is the optimum way to get the ideal roughness and hydrophilicity. Copyright © 2015 John Wiley & Sons, Ltd.