Membrane and Desalination Technologies - TCE Moodle Website

Preparation of Polymeric Membranes 59
Fig. 2.15 Chemical
structure of PEBAX.
3.11. Poly(phthalazine ether sulfone ketone)
Poly(phthalazine ether sulfone ketone) (PPESK) contains rigid aromatic rings and has
shown very good mechanical strength and chemical resistance, which chemical structure
is shown in Fig. 2.14. Its glass transition temperature is near 300 C. PPESK is a potential
membrane material for high temperature gas separation. It is also used to prepare ultrafiltration
and nanofiltration membranes for water treatment.
3.12. Polyether Block Amide
Polyether block amide (PE-b-PA) copolymer resin is a thermoplastic elastomer combining
linear chains of rigid polyamide segments interspaced with flexible polyether segments. The
commercial PE-b-PA copolymer resin is under the trademark PEBAX by Elf-Atochem,
which has the general chemical structure shown in Fig. 2.15.
Where PA is an aliphatic polyamide “hard block” (i.e. Nylon 6 [PA6] or Nylon 12 [PA-
12]) and PE is an amorphous polyether “soft block”. The soft segment is either polyether
oxide (PEO) or polytetramethylene oxide (PTMEO). This crystalline/amorphous structure
demonstrates properties of thermoplastics and elastic rubbers. Usually, the hard amide block
provides the mechanical strength of the prepared membranes, and the soft ether blocks mainly
favor the transport and separation characteristics.
4. PHASE INVERSION MEMBRANES
Fig. 2.14 Chemical structure of PPESK.
HO C
O
PA C O PE
Following the development of the first anisotropic membrane via precipitating a cellulose
acetate casting solution in a water bath by Loeb and Sourirajan in 1960s, different techniques
such as solute casting, interfacial polymerization and plasma polymerization have been
proposed to make selective, permeable anisotropic membranes during the past three decades.
Nevertheless, the phase inversion technique is still the most popular and important preparation
method, especially for commercial membrane productions. In the process of the phase
O
O H
n