Investigation of the effect of treatment with supercritical carbon dioxide on structure and properties of polypropylene microfiltration membranes

• Treatment of porous polypropylene membranes with supercritical CO2 was investigated.
• Two types of commercial polypropylene microfiltration membrane were tested.
• Effect of temperature, pressure, treatment time and decompression rate was studied.
• No destruction or significant changes of membranes’ key properties were detected.
• Supercritical CO2 is suitable for porous polypropylene membrane processing.

The effects of treatment with supercritical carbon dioxide of two types of polypropylene microfiltration membranes, which may occur in novel membrane processing techniques such as membrane cleaning using supercritical carbon dioxide as solvent, were investigated. The membranes were treated with scCO2 at three different pressures (8 MPa, 16 MPa, and 24 MPa) and at two various temperatures (40 °C and 70 °C) for different treatment times (5 min and 100  min). The morphology of the membranes was investigated using various analytical methods, using non-treated membranes as reference samples. No critical changes in membrane structure and properties, which would limit the usability of the membranes in microfiltration processes, were observed. Supercritical carbon dioxide can be safely applied in polypropylene membrane production, maintenance and modification.