Chemistry Reference
In-Depth Information
Table 2.
Degradation functions used in the IKP method.
[6]
Kinetic models
f
j
(
a
)
g
j
(
a
)
Observations
1
n
ð
ln
ð
1
aÞÞ
n
Nucleation and nucleus
growth
1
n
ð
1
aÞð
ln
ð
1
aÞÞ
S1-n
¼
1/4
S2-
n
¼
1/3
S3-
n
¼
1/2
S4-
n
¼
2/3
ð
1
aÞ
n
Phase boundary reaction
1
ð
1
aÞ
S6 Plane Symmetry
h
i
S7 Cylindrical Symmetry
1
=
2
21
ð
1
aÞ
h
i
S8 Spherical Symmetry
1
=
3
31
ð
1
aÞ
1
=
2
a
1
2
Diffusion
a
S9 Plane Symmetry
ð
1
aÞÞ
1
ð
1
aÞ
ln
ð
1
aÞþa
S10 Cylindrical Symmetry
ð
ln
h
i
1
2
=
3
S11 Spherical Symmetry
ð
1
aÞ
1
=
3
1
2
=
3
a ð
1
aÞ
3
=
2
1
h
i
1
h
i
2
S18 Jander's Type
1
=
3
aÞ
1
=
3
1
=
3
3
=
2
ð
1
aÞ
ð
1
1
ð
1
aÞ
1
Potential law
ð
1
=
n
Þa
1
n
a
n
ð
0
<
n
<
2
Þ
S12-n
¼
1/4
S13-
n
¼
1/3
S14-
n
¼
1/2
S17-
n
¼
3/2
Reaction order
ð
1
aÞ
ln
ð
1
aÞ
S5-n
¼
1
1
n
S15-n
¼
1/2
ð
1
=
n
Þð
1
aÞ
1
=
2
1
ð
1
aÞ
1
=
3
S16-n
¼
1/3
1
ð
1
aÞ
and Levchik
[8,9]
discussed the significance
of these values and demonstrated the
following relationships:
heating rates under nitrogen atmosphere.
Thermal decomposition proceeded in a
single step; however, for the higher heating
rate, a slight change in the slope as the
sample heats up can be seen. The main
decomposition step takes place in a broad
temperature range (680-780 K). Moreover,
the TGA thermograms of PA6/LLDPE/
SEBS-g-DEM shift towards the right as
the heating rate increases in the samples.
No significant difference could be noticed
between the thermograms with and without
the interfacial agent.
DTG curves of PA6/LLDPE/SEBS-g-
DEM are shown in Figure 2. Degradation
rates are being shifted to higher tempera-
tures due to the use of higher heating rates
which promote a difference in the tempe-
rature profile in the sample. As the heating
rate increases, there are some differences in
the occurrence of the degradation reaction
mechanisms. For instance, the DTG peak
shifts towards the right and decrease its
degradation rate as the heating rate incre-
ases (Figure 2(a)). On the other hand, PA6/
LLDPE DTG curves (Figure 2(b)) do not
exhibit a remarkable change on the degra-
dation rate, possibly due to the fact that
there is no interfacial area enough to reach
B
v
¼
log
ð
k
v
Þ
(3)
3
RT
v
Þ
1
l
v
¼ð
(4)
where k
v
is the rate constant at of the system
at the temperature
2
:
T
v
; these two parameters
are characteristic of
the experimental
conditions.
The curves log(k
v
)versus1/T
v
are plotted
in order to calculate the intercept and slope
of this equation:
log
ðk
v
Þ¼
log
A
in
ð ÞE
inv
=
2
:
3
RT
v
(5)
which finally results in the values of the
invariant activation energy and the pre-
exponential factor of the evaluated sample.
The probabilities associated with the 18
degradation functions proposed in the liter-
ature are presented in Table 2. The degra-
dations are complex phenomena and must
be represented by a set of functions instead
of a single one.
Results and Discussion
The thermograms of PA6/LLDPE/SEBS-g-
DEM are presented in Figure 1 for three
