Homework 1
1. By the use of a Langmuir-Blodgett method, very thin films can be prepared, and this
method may be useful for high selectivity but low permeability polymers. A thin film
o
with a thickness 10 A of special polymer processing an oxygen permeability of 1
Barrer [1 Barrer = 10 x 10-10 cm3(STP) / (cm2.s.cm Hg)] and nitrogen permeability of
0.02 Barrier deposited by this method on a composite membrane comprising an
asymmetric polysulfone (PSF) ultrafiltration membrane with a microporous layer
having an oxygen permeance of 0.2 cm3 (STP) / (cm2-s-cm Hg) and a 0.02 micron
dense layer having an oxygen permeability of 1.4 Barrers and nitrogen permeability of
0.25 Barrer covered with a coating of silicone rubber with an oxygen permeability 550
Barrers and a nitrogen permeabkility 260 Barrers. The silicone rubber has a thickness
of 1 micron above the PSF dense layer, and it has penetrated to all the defect pores in
the entire dense PSF layer with a defect pore area of 0.02 %, but does not coat the
microporous PSF layer.
1) What is the selectivity and oxygen flux for the special polymer layer exposing
to air (assuming a negligible pressure on the permeate side)?
2) Is it justifiable to neglect the permeation resistance of the microporous PSF
layer by comparing this resistance with the other resistances?
3) Calculate the oxygen fluxes and oxygen/nitrogen separation factors for the
following two composite membranes:
a. Silicone rubber-coated PSF membrane (three layers)
b. Special polymer layer onto the silicone rubber-coated PSF membrane
(four layers)
,
1. By the use of a Langmuir-Blodgett method, very thin films can be prepared, and this
method may be useful for high selectivity but low permeability polymers. A thin film
o
with a thickness 10 A of special polymer processing an oxygen permeability of 1
Barrer [1 Barrer = 10 x 10-10 cm3(STP) / (cm2.s.cm Hg)] and nitrogen permeability of
0.02 Barrier deposited by this method on a composite membrane comprising an
asymmetric polysulfone (PSF) ultrafiltration membrane with a microporous layer
having an oxygen permeance of 0.2 cm3 (STP) / (cm2-s-cm Hg) and a 0.02 micron
dense layer having an oxygen permeability of 1.4 Barrers and nitrogen permeability of
0.25 Barrer covered with a coating of silicone rubber with an oxygen permeability 550
Barrers and a nitrogen permeabkility 260 Barrers. The silicone rubber has a thickness
of 1 micron above the PSF dense layer, and it has penetrated to all the defect pores in
the entire dense PSF layer with a defect pore area of 0.02 %, but does not coat the
microporous PSF layer.
1) What is the selectivity and oxygen flux for the special polymer layer exposing
to air (assuming a negligible pressure on the permeate side)?
2) Is it justifiable to neglect the permeation resistance of the microporous PSF
layer by comparing this resistance with the other resistances?
3) Calculate the oxygen fluxes and oxygen/nitrogen separation factors for the
following two composite membranes:
a. Silicone rubber-coated PSF membrane (three layers)
b. Special polymer layer onto the silicone rubber-coated PSF membrane
(four layers)
,
