NAMS 2002 Workshop - ICOM 2008

EMS Barrer Prize – 4b
Thursday July 17, 10:45 AM-11:10 AM, Maui
New Challenges in membrane preparation by phase inversion technique
A. Figoli (Speaker), ITM-CNR, Rende, Italy - a.figoli@itm.cnr.it
The phase inversion technique allows producing both symmetric and asymmetric
(porous and dense) membranes. Prof. Heiner Strathmann gave his strong
contribution in this field, already in 1971, elaborating an original approach in
which the process of membrane formation is shown in a simplified way as a line
through the phase diagram [1-3]. Nowadays, the phase inversion technique still
represents the most used procedure for membranes preparation that are usually
employed in traditional separation processes from microfiltration/ ultrafiltration
(porous membranes) to nanofiltration/reverse osmosis/pervaporation/gas
separation (dense membranes). In this work, innovative polymeric membranes
prepared by this technique are presented for potential food, environmental,
pharmaceutical and chemical applications: a) a multilayer membrane film b)
polymeric capsules and c) elastomeric asymmetric SBS membranes. a) The
multilayer membrane was developed as an innovative antimicrobial food
packaging film [4-5]. The ´intelligent´ film should recognize the presence of
bacteria in the food and release an amount of antimicrobials suitable to inhibit
bacterial growth and prevent spoilage. The multilayer film is made of three layers:
1) an outer dense layer to control the exchange rate of gases and vapour
between the external and internal environment of the food packaging, 2) an
intermediate adhesive tie-layer which has also the function of reservoir of
antimicrobials, 3) a porous third layer, made by non-solvent induced phase
inversion (NIPS), which is able to control the release of antimicrobials to the food
in time. The release of antimicrobials can be adjusted changing the morphology
of the porous layer that can be controlled varying the phase inversion process
conditions. b) Polymeric capsules using a membrane process combined with the
phase inversion technique (NIPS) was exploited [6]. This method can be
identified as an integration between the traditional chemical capsule techniques
(coacervation or phase inversion) and the mechanical capsule technique
(pressure extrusion). It allows the formation of monodispersed polymer (modified
polyetheretherketone) micro-capsules with different morphologies. The capsule
morphology, porosity, size and shell thickness is easily adjusted changing the
ingredient parameters such as polymer concentration, solvent and non solvent
involved phases in the process. c) Novel asymmetric elastomeric SBS
membranes were prepared by NIPS [7] which allows to taylor the morphology of
the prepared membrane and to obtain a resistant membrane with a thin active
layer in a single step. The success of the preparation of asymmetric elastomeric
hydrophobic membranes leads to an easier membrane production at lower cost