Influence of the Processes Parameters on the Properties of The ...

Chapter 4.
Experimental Procedures and Protocols for Analyses
depressurizing valves or by <strong>the</strong> combination <strong>of</strong> both types <strong>of</strong> valves. The dP/dt procedure is quite tricky and
requires great skill. CO 2 is supplied by Air Liquid and is 99.5% pure.
2.1.2 Setup One: Filling <strong>the</strong> Chamber with Teflon ®
In this setup, three pellets are placed in <strong>the</strong> pressure chamber on perforated metal stages which are
encircled by a Teflon ® isolation material (cf. Figure 4.12-a). The pellets <strong>of</strong> upper, centre and bottom
compression moulding position (A, B and C) are placed in <strong>the</strong> upper, centre and bottom position in <strong>the</strong>
pressure chamber (A, B and C), respectively. Teflon ® material is placed into <strong>the</strong> pressure chamber in order
to decrease <strong>the</strong>ir volume which facilitates <strong>the</strong> depressurization rate.
2.1.3 Setup Two: Filling <strong>the</strong> Chamber with Glass Beads
The second procedure consists <strong>of</strong> filling <strong>the</strong> pressure chamber (until <strong>the</strong> ~ 1/3 or ~ 2/3 <strong>of</strong> <strong>the</strong>
height <strong>of</strong> <strong>the</strong> pressure chamber) with small glass balls (diameter 3 mm) and <strong>the</strong>n a perforated grill (hole
diameter 2 mm) is placed above <strong>the</strong>m. After that, <strong>the</strong> pellet is placed on <strong>the</strong> grill. This setting was adopted to
study <strong>the</strong> pore size difference at <strong>the</strong> top <strong>of</strong> <strong>the</strong> chamber as compared to three different points in <strong>the</strong> chamber
(cf. Figure 4.12-b).
Figure 4.12: Schematic representation <strong>of</strong> <strong>the</strong> cross section <strong>of</strong> <strong>the</strong> supercritical CO 2 chamber with two
different configurations.
For both procedures, after placement <strong>of</strong> <strong>the</strong> pellets, <strong>the</strong> temperature and pressure have been raised
to <strong>the</strong> required value. Then, pellets have been saturated with supercritical CO 2 during a desired time. After
that, <strong>the</strong> chamber has been depressurized with a given depressurization rate.
2.2 SEPAREX SFC6 scCO 2 Laboratory Plant
2.2.1 Experimental Device
The bigger volume <strong>of</strong> <strong>the</strong> chamber (6 L) allows increasing <strong>the</strong> number <strong>of</strong> samples (up to 15) in
one batch (cf. Figure 4.13). The process flow diagram is given in Figure 4.14.
2.2.2 Experimental Procedure
To begin experimentation <strong>the</strong> system is started four hours before <strong>the</strong> foaming process so that <strong>the</strong>
entire system might attain an equilibrium temperature. Sub-cooled liquid CO 2 is pumped by a volumetric
membrane pump (Milton Roy, maximum 5 kg/h), <strong>the</strong>n heated until <strong>the</strong> desired temperature and
continuously introduced into <strong>the</strong> mixing chamber. Experiments can be carried out in open-loop or closedloop
configuration, in which case, after condensation, CO 2 is recycled to <strong>the</strong> pump. Normally open loop
experimentation is carried out in this pilot plant. Temperatures and pressures are controlled, pressure being
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