Chemistry Reference
In-Depth Information
1
2
3
1040 cm
-1
500
1000
1500
2000
2500
3000
3500
(cm
-1
)
Figure 1.14
FTIR spectra of cured DER332/MPA-PCL530 systems at different
epoxide/anhydride equivalent ratios: (1) 3:2; (2) 4:2, (3) 5:2. Reproduced with
permission from H. Wang, X. Liu, J. Zhang and M. Xian,
Polymer International,
2009,
58
, 1435.
2009, John Wiley and Sons
[11]
The change in the structures of the cured epoxy resins with the stochiometric ratio
was also reflected in their thermal stability. The
T
5%
decreased continuously with
increasing epoxide:anhydride equivalent ratio. For the cured DER332/MPA-PCL530
resins, increasing the ratio from 3:2 to 4:2 and then to 5:2 resulted in
T
5%
deceasing
from 364.4 to 343.4 and then to 341.9 °C. The ether linkages of the polyether
homopolymer whose formation was favoured at higher epoxide:anhydride ratios, was
probably more susceptible to thermal degradation than the diester linkages formed
from the reaction of anhydride and epoxide.
Nonetheless, the starting temperatures
for thermal degradation for all samples were well above 300 °C, indicating fairly
good thermal stability. In addition,
T
5%
decreased with increasing molecular weight
of the PCL segment. This result was probably due to the decrease in crosslink density
as the PCL chain length increased.
