Membrane Gas Separation

13.2
Experimental 
13.2.1
Chemicals 
PEG with an average molecular mass of 300 
g 
mol 
−
1
and poly(ethylene oxide - co -
epichlorhydrine) (64 – 69 wt.% of epichlorhydrine) were purchased from Aldrich and used 
as received without further purifi cation (Figure 13.1 ). Pebax ® samples (extruded fi lms 
and granules) were given by Arkema. Pebax ® are polyamide block polyether copolymers 
(cf. Figure 13.2 ) and their molecular weight ( M
w
) are between 30 000 and 50 000 g mol 
−
1
.

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CO
2
 Permeation with Pebax®-based Membranes for Global Warming Reduction
259
13.2.2
Membranes 
Extruded fi lms provided by Arkema were directly used for the permeation studies of 
Pebax ® . 
Pebax ® and PEG or PEGEPI blend membranes were prepared by solution casting and 
solvent evaporation techniques. The blend solutions were prepared by thoroughly mixing 
their individual solutions in different ratios. We only used limpid solutions, i.e. solutions 
without phase separation. The bubble - free blend solution was cast to the desired thickness 
on a glass plate pre - heated to 100 ° C, and the solvent N - methyl pyrrolidone (NMP) was 
allowed to evaporate slowly at 100 ° C for a period of 24 hrs. We consider NMP as the 
best solvent for Pebax ® 1657, the main polymer used in the present study, since its 
Hildebrand solubility parameter value (22.9 MPa 
1/2
) coincides with that of the polymer 
(22 MPa 
1/2
). Due to the semi - crystalline nature of Pebax ® , heating was still needed for 
thorough polymer dissolution. The membranes were designated by their relative weight 
percentage in the blend, with the numbers given in the same order as that of their abbrevi-
ated name. 
The fi lm thickness was determined by means of a Mitutoyo ® micrometer. To obtain 
reliable values, the thickness was determined in nine places on each sample.