Characterizations
Thermal and thermogravimetric analyses of the hybrids were conducted under N 2
atmosphere using DuPont 910 equipment (New Castle, DE, USA). The samples
were heated and cooled at a rate of 20
C/min. Wide-angle X-ray diffraction (XRD)
measurements were performed at room temperature on a Rigaku (D/Max-IIIB) X-ray
diffractometer (Tokyo, Japan) using Ni-filtered Cu-Kα radiation. The scanning rate
was 2
/min over a range of 2θ = 2–14
.
The tensile properties of the extrudate were determined using an Instron Mechanical Tester(Model 5564) (Norfolk County, USA) at a crosshead speed of 2 mm/min.
The specimens were prepared by cutting strips 5 Â 70 mm
2 in size. An average of at
least eight individual determinations was obtained. The experimental uncertainties in
the tensile strength and modulus were Æ1 MPa and Æ0.05 GPa, respectively.
A polarizing microscope (Leitz, Ortholux) (Lahn-Dill-Kreis, Germany) equipped
with a Mettler FP-5 hot stage was used to examine the liquid crystalline behavior.
The morphology of the fractured surfaces of the extrusion samples was investigated
using a Hitachi S-2400 scanning electron microscope (SEM) (San Jose, CA, USA).
The fractured surfaces were sputter-coated with gold for enhanced conductivity
using an SPI Sputter Coater. Transmission electron microscope (TEM) photographs
of ultrathin-section polymer/organoclay hybrid samples were taken on an EM
912 OMEGA (Carl Zeiss) TEM (Tokyo, Japan) using an acceleration voltage of
120 kV.
Results and Discussion
Dispersibility of Organoclay in TLCP
Figure 3 shows the XRD patterns of C25A organoclay, pure EHBT, and their EHBT
hybrids with 2–6 wt% C25A for 2θ = 2–14
. The observed interlayer spacing was
2θ = 5.64
(d = 15.67 Å) for C25A. A peak was observed at 2θ = 4.69
(d = 18.84 Å) for pure EHBT. As the amount of organoclay increased from 2 to
6 wt%, C25A/EHBT hybrids showed the same peak at the same position
(2θ = 4.69
). No obvious clay peaks appeared in the XRD curves of the EHBT
hybrids with 2–6 wt% C25A. This indicated that these clay layers were exfoliated
and dispersed homogeneously in the TLCP matrix. This was also direct evidence
that the C25A/EHBT hybrids formed nanocomposites.
The XRD results for the pristine clay, organoclay, and C18-MMT/OBDT nanocomposites are shown in Fig. 4. The d 001 reflection for Na
+
-MMT was observed at
2θ = 7.38
, which corresponds to an interlayer distance of 11.98 Å. The XRD peak
for the organically modified clay, C18–MMT, appeared at 2θ = 4.14
, corresponding
to an interlayer distance of 21.35 Å. As expected, ion exchange between Na
+
-MMT
and octadecylamine chloride (C18-Cl
À ) increases its basal interlayer spacing over
that of pristine Na
+
-MMT and shifts the diffraction peak greatly toward lower values
of 2θ. Surface modification by alkylamine produced substantially larger interlayer
588
T. Y. Ha et al.
Thermal and thermogravimetric analyses of the hybrids were conducted under N 2
atmosphere using DuPont 910 equipment (New Castle, DE, USA). The samples
were heated and cooled at a rate of 20
C/min. Wide-angle X-ray diffraction (XRD)
measurements were performed at room temperature on a Rigaku (D/Max-IIIB) X-ray
diffractometer (Tokyo, Japan) using Ni-filtered Cu-Kα radiation. The scanning rate
was 2
/min over a range of 2θ = 2–14
.
The tensile properties of the extrudate were determined using an Instron Mechanical Tester(Model 5564) (Norfolk County, USA) at a crosshead speed of 2 mm/min.
The specimens were prepared by cutting strips 5 Â 70 mm
2 in size. An average of at
least eight individual determinations was obtained. The experimental uncertainties in
the tensile strength and modulus were Æ1 MPa and Æ0.05 GPa, respectively.
A polarizing microscope (Leitz, Ortholux) (Lahn-Dill-Kreis, Germany) equipped
with a Mettler FP-5 hot stage was used to examine the liquid crystalline behavior.
The morphology of the fractured surfaces of the extrusion samples was investigated
using a Hitachi S-2400 scanning electron microscope (SEM) (San Jose, CA, USA).
The fractured surfaces were sputter-coated with gold for enhanced conductivity
using an SPI Sputter Coater. Transmission electron microscope (TEM) photographs
of ultrathin-section polymer/organoclay hybrid samples were taken on an EM
912 OMEGA (Carl Zeiss) TEM (Tokyo, Japan) using an acceleration voltage of
120 kV.
Results and Discussion
Dispersibility of Organoclay in TLCP
Figure 3 shows the XRD patterns of C25A organoclay, pure EHBT, and their EHBT
hybrids with 2–6 wt% C25A for 2θ = 2–14
. The observed interlayer spacing was
2θ = 5.64
(d = 15.67 Å) for C25A. A peak was observed at 2θ = 4.69
(d = 18.84 Å) for pure EHBT. As the amount of organoclay increased from 2 to
6 wt%, C25A/EHBT hybrids showed the same peak at the same position
(2θ = 4.69
). No obvious clay peaks appeared in the XRD curves of the EHBT
hybrids with 2–6 wt% C25A. This indicated that these clay layers were exfoliated
and dispersed homogeneously in the TLCP matrix. This was also direct evidence
that the C25A/EHBT hybrids formed nanocomposites.
The XRD results for the pristine clay, organoclay, and C18-MMT/OBDT nanocomposites are shown in Fig. 4. The d 001 reflection for Na
+
-MMT was observed at
2θ = 7.38
, which corresponds to an interlayer distance of 11.98 Å. The XRD peak
for the organically modified clay, C18–MMT, appeared at 2θ = 4.14
, corresponding
to an interlayer distance of 21.35 Å. As expected, ion exchange between Na
+
-MMT
and octadecylamine chloride (C18-Cl
À ) increases its basal interlayer spacing over
that of pristine Na
+
-MMT and shifts the diffraction peak greatly toward lower values
of 2θ. Surface modification by alkylamine produced substantially larger interlayer
588
T. Y. Ha et al.