NAMS 2002 Workshop - ICOM 2008

Pervaporation and Vapor Permeation II – 6
Thursday July 17, 5:00 PM-5:30 PM, Moloka’i
Pervaporation Performance of PDMS-grafted Aromatic Polyamide
Membrane Exhibiting High Durability and Processability
C. Yun (Speaker), Tokai University, Kanagawa, Japan
Y. Nagase, Tokai University, Kanagawa, Japan - yunagase@keyaki.cc.u-tokai.ac.jp
Pervaporation is a promising membrane technique for the removal of organic
molecules from their aqueous solutions. In earlier investigations, the
pervaporation process was applied to separate alcohol by water-selective
permeation through membranes, which has been already used in industries.
However, it is more practical to separate alcohol by using an alcohol-
permselective membrane, because alcohol is a minor component in the
fermentation product. Furthermore, if a practical organic-permselective
membrane is obtained, the pervaporation technique is expected to be an efficient
method for the removal or the recovery of organic components from waste fluid
or industrial drainage. To achieve the selective permeation of organic
components in the pervaporation of aqueous solutions of organic liquids, it is
very important to enhance the solubility of alcohol over water in a polymer
membrane because of the higher diffusivity of water as compared with alcohol. In
addition, the durability of the membrane against several organic solvents is more
important, because the organic component was concentrated in the inert of the
membrane during the permeation. A crosslinked polydimethylsiloxane (PDMS)
membrane, has been known to show a selective permeation of alcohol at the
pervaporation of an aqueous alcohol solution. Such a separation property of
PDMS membrane is due to the high hydrophobicity of the membrane surface and
the high permeability of vapors through the membrane. However, it is not a
practical membrane because an ultrathin membrane to achieve a high flux
cannot be prepared from the crosslinked material. Therefore, we have prepared
some soluble PDMS- grafted copolymers having a rigid backbone component
that showed an improved mechanical property and organic-permselectivity. In
our previous work, we have developed a siloxane-grafted polyamide (PA-g-
PDMS) by the polycondensation of 3,5-bis(4-aminophenoxy)benzyloxypropyl-
terminated polydimethylsiloxane (BAPB- PDMS) and terephthaloyl chloride,
which exhibited a high organic permselectivity in the pervaporation of aqueous
organic liquid solutions with a stable permeation. However, in the case of PA-g-
PDMS, when the reprecipitated polymers were filtered and dried in vacuo, they
became insoluble in all solvents. In other words, this membrane possessed poor
processability due to the chemical structure of the backbone component. In this
study, a chemical modification of the main chain structure of PDMS- grafted
polyamide has been investigated to enhance the processability of the copolymer,
with maintaining the durability to organic components. For this purpose, the