Chemistry Reference
In-Depth Information
40
35
30
25
5 K/min
15 K/min
20 K/min
20
15
10
5
0
0
100000
200000
300000
400000
500000
600000
E
jv
(J/mol)
Figure 3.
Compensation effect observed in PA6/LLDPE/SEBS-g-DEM.
The invariant kinetic parameters obtain-
ed are depicted in Table 3. These results
show that the addition of the interfacial
agent in the PA6/LLDPE blend improves
the thermal stability of the material.
The calculated invariant activation
energy for the PA6/LLDPE/SEBS-g-DEM
was 540 KJ/mol, which shows an increase of
nearly 100% when compared to that of the
PA6/LLDPE blend. This could be due to
the better phase dispersion achieved when
the SEBS-g-DEM is added to the blend,
which is somehow improving the thermal
stability of the material. Additionally,
the IKP method allowed determining the
probabilities of several degradation mecha-
nisms to occur. The kinetic models assumed
in the thermal decomposition are shown in
Table 2.
Degradation profiles are governed by
a combination of nucleation and phase
boundary reactions in both of the studied
blends. The probabilities of phase bound-
ary reaction and nucleation mechanisms
(Figure 4 and 5) were raised by 26%,
accounting for an increase of the surface
area between PA6 and LLDPE on the
samples, evidencing that SEBS-g-DEM
could effectively be acting as a compatibi-
lizing agent in this blend, supporting the
increase of the Ea. The Molau test also
evidenced this phenomenon. Differences
on material reactivities cause the blend to
exhibit a thermal resistance.
[13]
Nucleation
and nucleus growing reaction mechanisms
were the most probable to take place in
both samples, with and without SEBS-g-
DEM.
On the other hand, Figure 6 presents the
dependence of the kinetic functions taking
place in the degradation with the degree of
conversion achieved by the material. The
equation plotted in Figure 6 is given by:
f ðaÞ¼
X
j
Table 3.
Invariant kinetic parameters obtained by the IKP
method.
1
to
18
ð
%
Þf
j
ðaÞ
(6)
¼
Sample
E
inv
(KJ/mol)
log A
inv
PA6/LLDPE
283
19.03
The continuous line represents the
behavior of the PA6/LLDPE, while the
PA6/LLDPE/SEBS-g-DEM
519
35.15
