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

Chapter 5.
Characterization <strong>of</strong> Scaffolds for Connective Tissue Engineering
Table 5.12: Variation domain <strong>of</strong> <strong>the</strong> various factors.
Level T sat (°C)
P sat dP/dt
(bars) (bar/s)
t sat (min) PLGA 50:50 /PLGA 85:15
- 1 36.5 100 1 20 100/0
+ 1 60 250 20 20 0/100
Table 5.13: 2 4 design <strong>of</strong> experiments: levels <strong>of</strong> factors and average size <strong>of</strong> pores.
Experiment X 1 X 2 X 3 X 4
T
(°C)
P
(bar)
dP/dt
(bar/s)
PLGA
50:50/85:15
Pore
Diameter
(μm)
1 -1 -1 -1 -1 36.5 100 1 100/0 153
2 -1 -1 -1 1 36.5 100 1 0/100 264
3 1 -1 -1 -1 60 100 1 100/0 130
4 1 -1 -1 1 60 100 1 0/100 187.5
5 -1 1 -1 -1 36.5 250 1 100/0 30.3
6 -1 1 -1 1 36.5 250 1 0/100 72.5
7 1 1 -1 -1 60 250 1 100/0 27
8 1 1 -1 1 60 250 1 0/100 59
9 -1 -1 1 -1 36.5 100 20 100/0 367.5
10 -1 -1 1 1 36.5 100 20 0/100 71
11 1 -1 1 -1 60 100 20 100/0 151.5
12 1 -1 1 1 60 100 20 0/100 108
13 -1 1 1 -1 36.5 250 20 100/0 4
14 -1 1 1 1 36.5 250 20 0/100 25
15 1 1 -1 -1 60 250 1 100/0 23
16 1 1 -1 1 60 250 1 0/100 36
17 -1 1 -1 -1 36.5 250 1 100/0 47
18 1 1 -1 1 60 250 1 0/100 61
19 -1 -1 -1 0 36.5 100 1 50/50 258
20 1 -1 -1 0 60 100 1 50/50 60
21 -1 -1 1 0.5 36.5 100 20 25/75 93.5
22 1 -1 1 0.5 60 100 20 25/75 110
23 -1 1 1 -0.5 36.5 250 20 75/25 3
24 1 1 -1 -0.5 60 250 1 75/25 23
25 -1 1 -1 0.5 36.5 250 1 25/75 30
26 -1 1 -1 0 36.5 250 1 50/50 36
27 -1 1 -1 -0.5 36.5 250 1 75/25 22.5
28 -1 -1 1 0 36.5 100 20 50/50 222
29 -1 -1 1 -0.5 36.5 100 20 75/25 275
The first 2 4 = 16 values allow us to calculate <strong>the</strong> coefficients <strong>of</strong> <strong>the</strong> two first order models reported
on <strong>the</strong> Table 5.14, <strong>the</strong> o<strong>the</strong>r values play a role to valid <strong>the</strong> first order model:
y = a 0 + a 1 X 1 + a 2 X 2 + a 3 X 3 + a 4 X 4 + a 12 X 1 X 2 + a 13 X 1 X 3 + a 23 X 2 X 3
For both blends, it is important to note that <strong>the</strong> most influent factor is <strong>the</strong> pressure (a 2 ). For
PLGA 50:50 <strong>the</strong> saturation temperature (a 1 ) is also an influent effect while it is non influent for <strong>the</strong> PLGA 85:15 .
It is <strong>the</strong> contrary for factor 3, as <strong>the</strong> detail given in Table 5.14.
The variation <strong>of</strong> average pore diameter as a function <strong>of</strong> PLGA 50:50 fractions in <strong>the</strong> blends (cf.
Figure 5.13), for experiments performed in <strong>the</strong> same operating conditions, shows that with increasing
amount <strong>of</strong> PLGA 50:50 , <strong>the</strong> average pore size increases when high depressurization rate (20 bar/s) is applied.
Analysis <strong>of</strong> <strong>the</strong> average diameter <strong>of</strong> pores presented in Table 5.13, showed us that to have a trend for bigger
- 127 -