Biomedical Engineering Reference
In-Depth Information
to PLA/PCL blends effectively improves their immiscibility (Takayama, 2006a, 2006b;
Harada, 2007, 2008) and therefore the fracture energy (Takayama, 2006a, 2006b).
FE-SEM micrographs of cryo-fractured surfaces of PLA/PCL and PLA/PCL/LTI are shown
in Fig.13. The content of PCL was 15wt% in these materials. Spherical features appeared on
the micrograph are thought to be PCL-rich phases. These micrographs clearly showed that
the size of the PCL-rich phase dramatically decreases by LTI addition. It is thus presumed
that LTI addition effectively improves the miscibility of PLA and PCL.
This is thought to be
related to the following chemical reaction, that is, the hydroxyl group of PLA and the
isocyanate group of LTI creates urethane bond:
HO-R' + R-N=C=O → R-NHCOO-R'
(a)PLA/PCL (b)PLA/PCL/LTI
Fig. 13. FE-SEM micrographs of cryo-fracture surfaces of PLA/PCL and PLA/PCL/LTI.
4
3
2
P
LA
1
0
0
0.5
1
1.5
2
LTI content [phr]
Fig. 14. Dependence of LTI content on the molecular weight.
Dependence of LTI content on the molecular weight,
M
w
, is shown in Fig.14
．
For
comparison,
M
w
of neat PLA is also shown in the figure.
M
w
values of the blends tend to
