Microporous membranes from polyolefin-polyamide blend materials

An alternative method using established polymer processing and membrane formation processes to prepare hydrophilic membranes based on acid modified polyolefins is introduced. This process includes blend formation by reactive extrusion of functionalized polyolefins (polypropylene; PP) and a hydrophilic polyamide (PA). In a first step the pore formation is realized by extracting non-covalently bound polyamide. The resulting membranes are tested by pure water as well as protein filtration. The properties are discussed in terms of permeate flux, retention capability and fouling behavior.

Reactive blending of hydrophobic and hydrophilic materials like polypropylene and polyamide is a suitable approach to prepare membranes with good mechanical and chemical stability combined with low fouling properties. The pores in those blend membranes have been prepared by selective extraction of PA non-covalently bound to the PP matrix. Permeate flux through membranes depends on PA content in the initial blend material, extraction time and remaining PA in the final membrane. The latter causes a flux decline due to swelling when in contact with aqueous systems. On the other hand smaller effective pore sizes during the filtration process resulted in a lower fouling by proteins and a higher relative flux recovery of the membranes after protein filtration. In other words, the effective pore size and therefore the filtration properties can be easily controlled with the introduced PP/PA blend membranes. Future work will concentrate on the reduction of polyamide swelling and the production of a more uniform pore size.