Membrane Gas Separation

13.2.4
Gas Sorption Measurements 
The gas uptakes were measured with an electronic microbalance, IGA model 002, sup-
plied by Hiden Analytical, Warrington (England). After transferring a fl at piece of mem-
brane to the sample pan, the system was evacuated for several days by turbo - molecular 
pump to evacuate all traces of volatile substances, until a stable weight was reached. The 
sample environment temperature was controlled by a sensor and a thermostatic water 
bath. A gas at a controlled pressure was fed to the sample chamber, and the sample weight 
was monitored as a function of time, until a stable weight was obtained. Afterward, several 
successive pressure levels can be applied and the successive equilibrium mass gains allow 
one to draw the gas sorption isotherm: 
mass gain = f (pressure applied)

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2
 Permeation with Pebax®-based Membranes for Global Warming Reduction
261
13.2.5
Thermal Behaviour Studies by DSC (Differential 
Scanning Calorimetry) 
The thermal behaviour of samples was analyzed by using the conventional differential 
scanning calorimeter (DSC Q100 TA Instruments). Samples with a mass of about 10 mg 
were used. The heating step was done from
−
90 ° C to 220 ° C at a rate of 10 ° C/min fol-
lowed by an isothermal heating for 10 min, a fi rst cooling from 220 ° C to
−
90 ° C, and a 
second heating in the same range. All DSC runs were carried out under nitrogen atmos-
phere to minimize the oxidative degradation. Before all DSC experiments, the baseline 
was calibrated using empty aluminium pans, and the DSC apparatus was calibrated using 
the melting temperature and enthalpy of a high - purity indium standard (156.6 ° C and 
28.45 J g 
−
1
). 
The degree of crystallinity ( X
c
) was determined with the following equation:
X
H
H
c
m
m
%
( )
=
(
)
100
0
Δ
Δ
where  
Δ
 H
m
is the melting enthalpy per gram of polyamide 12 phase in the membrane 
sample,
Δ
H
m
0
is the extrapolated value of the enthalpy corresponding to the melting of 
100% crystalline (
Δ
H
m
J g
0
1
246
=
−
for PA12 and 230 J g 
−
1
for PA6) [30] .