Chemistry Reference
In-Depth Information
Table 1.
Conditions used in blending and SEBS grafting.
Condition
Grafting
Mixing
Temperature profile (
8
C)
238-227-238-238-238
130-225-238-218-216
Melt Temperature (
8
C)
244
232
Die Temperature (
C)
225
225
8
Pressure drop (psi)
1000
750
Screw rate (rpm)
50
110
initiator under the conditions shown in
Table 1. The grafting degree achieved in
SEBS-g-DEM functionalization lies around
0.4 wt %. This grafting degree was deter-
mined according to Rosales et al.
[5]
samples using a Philips 505 microscope.
Samples were metallized with
gold-
palladium.
by
Invariant Kinetic Parameters (IKP)
Method
[8,9,10]
To determine the invariant activation energy
(
FTIR and a calibration curve.
The PA6/LLDPE (20/80% wt., respec-
tively) and PA6/LLDPE/SEBS-g-DEM
blends were prepared in a Werner & Pflei-
derer ZSK-30 corotating twin-screw extru-
der under the conditions shown in Table 1.
The compatibilizer (SEBS-g-DEM) was
added at a concentration of 5% wt. Irganox
B-1171 and Irganox 1098 were added
before melt blending (0.5 and 0.25% wt.,
respectively) to avoid thermal degradation
during processing.
A
inv
)
the rate expression, d
a
/dt, was assumed to
be equal to the following equation:
E
inv
) and the pre-exponential factor (
d
t
¼
d
k
f
ðaÞ
(1)
where
is the degree of conversion and
k ¼ A
exp
ðE=RTÞ
according to Arrhe-
nius law.
Eighteen apparent activation energies
(E
iv
) and pre-exponential factors (A
iv
) were
determined employing the Coats-Redfern
method.
[11]
The IKP method is based on
the principle of the compensation effect
quite well reviewed in the literature. For
each function
a
Thermogravimetric Analysis (TGA)
Thermograms were obtained by thermo-
gravimetric analysis on a Mettler-Toledo
TGA/STDA851
e
thermal analyzer under
the following conditions: samples of 10 mg
each were heated up to a temperature of
800 K under nitrogen atmosphere and vari-
ous heating rates (
b
i
¼
5, 15 and 20
8
C/min).
Subsequently, thermal kinetic para-
meters were determined by means of the
Invariant Kinetic Parameters method.
[6]
) proposed by the method,
log(A
j
) versus E
j
is plotted. If a compen-
sation effect is observed, then a linear
relationship is seen for each heating rate
b
v
,
which is defined by the following expres-
sion:
f
j
(
a
log
A
iv
¼ B
v
þ l
v
E
jv
(2)
Molau Test
The Molau test
[7]
was performed on the
blends in order to determine if there was a
possible compatibilizing effect. Samples of
the blends were dissolved in concentrated
formic acid (2% w/v solution) and allowed
to rest for 8 h at room temperature.
where
E
jv
are the apparent pre-
exponential factor and the activation energy,
respectively, calculated using a function
f
j
(
A
iv
and
b
v
.
Inappropriate assigning of the kinetic
model function results in the distortion of
the kinetic parameters and in the false or
superficial classification of the compensa-
tion effect.
The values
a
)at
Scanning Electron Microscopy
Scanning ElectronMicroscopy (SEM) anal-
yses were carried out on the cryogenically-
fractured surface of compression-molded
l
v
are calculated from
the intercept and the slope of the straight
lines obtained by Equation (2). Lesnikovich
B
v
and
