Page 229 - Biodegradable Polyesters

8.8 Fiber Biodegradability 207

14
PLA/15% HMW PCL/ TCH
12 PLA/9% HMW PCL/ TCH
PLA/ TCH
10 15% HMW PCL/ TCH
Mass loss (%) 8

6

4

2

0
0 50 100 150 200 250 300 350
Degradation time (h)
Figure 8.10 Mass loss of TCH-loaded electrospun fiber mats using chloroform/methanol
during the fiber degradation.

8.8
Fiber Biodegradability

The biodegradation behavior of TCH-loaded fiber mats, based on pristine
PLA, neat 15% HMW PCL, and PLA/9% HMW PCL blends, is depicted in
Figure 8.10. After the degradation in PBS for the initial 3–6 h, the mass loss
of all batches of fiber mats is very minimal. Even up to 24 h, the mass losses
detected are 0.2%, 0.36%, and 1.37% for neat 15% HMW PCL, PLA/15% HMW
PCL, and PLA/9% HMW PCL, respectively, apart from much greater loss
from pristine PLA at 3%. The increasing trend of mass loss does not seem
significant, as evidenced by further mass losses of only 6.26% and 2.91%
over the degradation time of 336 h, respectively, for the two aforementioned
PLA/HMW PCL blends. A similar tendency is clearly indicated for PLA/TCH
and 15% HMW PCL/TCH as highest and lowest mass losses at 12.5% and
1.8%. The plausible interpretation for the behavior of PLA/HMW PCL blends
is that increasing the PCL concentration up to 15%/v may preclude the water
penetration inside the fibers, thus resulting in slow water absorption due to
hydrophobicity and semicrystalline behavior of PCL. As clearly seen from
Table 8.3, it is manifested that mat samples with PLA/15% HMW PCL have
a much higher degree of crystallinity than those with PLA/9% HMW PCL.
The amorphous regions, where random and less tightly packed arrangement
of molecular chains occurs, become easily degraded as opposed to crystalline
regions. That is also why overall highest mass loss is obtained in biodegrad-
ability tests for pristine PLA fiber mats with much more amorphous phases