Influence of the Processes Parameters on the Properties of The ...
Influence of the Processes Parameters on the Properties of The ...
Influence of the Processes Parameters on the Properties of The ...
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Chapter 5.<br />
Characterizati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> Scaffolds for C<strong>on</strong>nective Tissue Engineering<br />
Table 5.20: Variati<strong>on</strong> in <str<strong>on</strong>g>the</str<strong>on</strong>g> average size <str<strong>on</strong>g>of</str<strong>on</strong>g> pores with different dP/dt values at P sat = 100 bars.<br />
Height <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> glass<br />
balls in <str<strong>on</strong>g>the</str<strong>on</strong>g> chamber<br />
dP/dt (bar/s)<br />
Pore Diameter<br />
(µm)<br />
Average Diameter<br />
Pore (µm)<br />
~2/3 10<br />
19.0<br />
18.9<br />
18.9<br />
~2/3 5<br />
50.7<br />
54.0<br />
52.4<br />
~2/3 1,25<br />
138.0<br />
127.9<br />
133.0<br />
~2/3 0,625 255.7 255.7<br />
3.2.3.2 Discussi<strong>on</strong> <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> Effect <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> Various CO 2 Process <str<strong>on</strong>g>Parameters</str<strong>on</strong>g><br />
As shown in Figure 5.17, for dP/dt = 5 bar/s, <str<strong>on</strong>g>the</str<strong>on</strong>g> estimated geometrical porosity (equati<strong>on</strong> 3.11) is<br />
decreasing when <str<strong>on</strong>g>the</str<strong>on</strong>g> dP/dt is increasing and it reaches a plateau at 92%, and 89.3% for saturati<strong>on</strong> pressures<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> 100 and 125 bars. <strong>The</strong> very close porosity values at 5 bar/s and 10 bar/s can also be explained by <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
coalescence <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> pores during CO 2 desorpti<strong>on</strong>. Our observati<strong>on</strong>s <strong>on</strong> pore size and <str<strong>on</strong>g>the</str<strong>on</strong>g> porosity (<str<strong>on</strong>g>the</str<strong>on</strong>g><br />
swelling) <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> polymer has shown us that with great pore sizes comes great porosity and with small pore<br />
size comes small porosity. This behaviour is in agreement with <str<strong>on</strong>g>the</str<strong>on</strong>g> literature [Beckman, 2004]. To our<br />
knowledge, it is impossible to create big pores with small polymer volume or small pores with important<br />
polymer swelling.<br />
Porosity[1-( f<br />
/ p<br />
)] ( %)<br />
98<br />
96<br />
94<br />
92<br />
90<br />
88<br />
PLGA 50:50<br />
Porosity Variati<strong>on</strong><br />
P sat<br />
100 bar<br />
P sat<br />
125 bar<br />
0 2 4 6 8 10 12<br />
dP/dt (Bar/s)<br />
Figure 5.17: Variati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> porosity <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> foams as a functi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> depressurizati<strong>on</strong> rate.<br />
<strong>The</strong> physical shapes <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> scaffolds prepared without volume c<strong>on</strong>straint were perfectly circled<br />
and visually homogenous. On <str<strong>on</strong>g>the</str<strong>on</strong>g> o<str<strong>on</strong>g>the</str<strong>on</strong>g>r hand, <str<strong>on</strong>g>the</str<strong>on</strong>g> shape <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> scaffolds processed with volume c<strong>on</strong>straint<br />
was corrupted. We have also observed homogeneity <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> SEM images. As shown in Figure 5.18, <str<strong>on</strong>g>the</str<strong>on</strong>g> pore<br />
size is smaller in high rates <str<strong>on</strong>g>of</str<strong>on</strong>g> depressurizati<strong>on</strong> and it increases with dP/dt increases. On <str<strong>on</strong>g>the</str<strong>on</strong>g> o<str<strong>on</strong>g>the</str<strong>on</strong>g>r hand,<br />
according to micrographs <str<strong>on</strong>g>the</str<strong>on</strong>g> interc<strong>on</strong>nectivity and homogeneity are observed in <str<strong>on</strong>g>the</str<strong>on</strong>g> cross-secti<strong>on</strong><br />
micrographs <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> scaffolds. However, <str<strong>on</strong>g>the</str<strong>on</strong>g> SEM images are not sufficient to have a real characterizati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
interc<strong>on</strong>nectivity.<br />
As menti<strong>on</strong>ed previously, we have observed that both <str<strong>on</strong>g>the</str<strong>on</strong>g> volume <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> pressure chamber and <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
positi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> pellet are important factors, which affect <str<strong>on</strong>g>the</str<strong>on</strong>g> pore size. For this reas<strong>on</strong>, <str<strong>on</strong>g>the</str<strong>on</strong>g> 5 remaining<br />
experiments are carried out in order to re-complete <str<strong>on</strong>g>the</str<strong>on</strong>g> Doehlert’ plan according to <str<strong>on</strong>g>the</str<strong>on</strong>g> new experimental<br />
setup with glass balls. <strong>The</strong> height <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> glass balls was at ~2/3 <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> height <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> pressure chamber for all<br />
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