Chemistry Reference
In-Depth Information
MICROMETRIC VALVE
CALIBRATED
CELL
V
3
MANOMETER 9015K
COMPRESSOR
MAXIMATOR
RUPTURE
DISC
VACUUM PUMP
GAS
HIGH EQUILIBRIUM
PRESSURE CELL
V
2
HIGH PRESSURE
GAS RESERVOIR
V
1
Fig. 2 Three cell principle for
pVT
measurements, after Sato et al. [
14
]. The high pressure line
connects the three cells: the high pressure reservoir cell (
V
1
), the high pressure equilibrium cell
housing the VW sensor (
V
2
), and the high pressure calibrated transfer cell (
V
3
)
calibrated transfer cell
V
3
to the equilibrium cell
V
2
, which contains the polymer.
Initial
p
i
and final
p
f
pressures are recorded between each transfer. The initial
methodology was based on the iterative calculation described by Hilic et al. [
18
,
19
]. The (rigorous) working equation (
2
) for the
pVT
technique gives the amount of
gas entering the polymer sample during the first transfer, once equilibration is
attained:
M
g
R
p
f
M
g
R
p
i
Z
i
T
i
V
3
p
f
Z
f
T
f
m
sol
¼
T
f
Z
f
D
V
pol
þ
V
2
þ
V
3
V
pol
:
(2)
Equation 2 permits calculation of the mass
m
sol
of gas dissolved in the
polymer.
M
g
is the molar mass of the dissolved gas.
Z
i
and
Z
f
are the compression
factors of the gas entering the polymer at the initial and final equilibrium sorption
conditions, respectively. Volume of the degassed polymer and the volume change
due to sorption are represented by
V
pol
and
D
V
pol
, respectively. The total amount
