Processing of Clay/Epoxy Nanocomposites with A Three-Roll Mill Machine
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Processing of Clay/Epoxy Nanocomposites with A Three-Roll Mill Machine Asma Yasmin, Jandro L. Abot and Isaac M. Daniel Center for Intelligent Processing of Composites, Northwestern University, Evanston, IL 60208-3040, U.S.A. ABSTRACT In the present study, a three-roll mill machine was used to disperse/exfoliate the nanoclay particles in an epoxy matrix. The compounding process was carried out with varying mixing time and concentrations of clay particles (1 to 10 wt.%). It was found that the longer the mixing time, the higher the degree of intercalation. Mechanical properties, XRD and TEM were used to characterize the nanocomposites. Elastic modulus was found to increase with increasing clay content, however, the tensile strength was not found to vary accordingly. Compared to conventional direct and solution mixing techniques, the compounding of clay/epoxy nanocomposites by a three-roll mill was found to be highly efficient in achieving higher levels of intercalation/exfoliation in a short period of time and also environmentally friendly. INTRODUCTION Over the last decade, polymer based composites containing nano-scale layered silicate clay particles have drawn significant attention [1-11]. This is mainly because the addition of a small amount of clay particles (2 wt.%) show pronounced peaks from silicate basal planes (d001) with d-spacing slightly lower than the composite containing 1 wt.% of clay. Therefore, the absence of peak in the case of 2 wt.% clay nanocomposite needs further confirmation by SAXS or low speed WAXD patterns. In general, the lower d-spacing at higher
Relative Intensity
3.53 nm
10% 3.6 nm
3.4 nm
5% 3% 2%
3.66 nm 1
2
1% 3
4
5
6
Diffraction angle, (2θ)
Figure 2. WAXD patterns of nanocomposites with varying clay contents.
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a
2 µm
b
20 nm
Figure 3. TEM images of 1 wt.% clay nanocomposite. (a) Low mag.; (b) high mag.
a
2 µm
b
20 nm
Figure 4. TEM images of 10 wt.% clay nanocomposite. (a) Low mag.; (b) high mag.
clay content is attributed to the increased intercalating sites with increased clay content that might impede the exfoliation of individual silicate layers [9]. Therefore, it can be suggested that the 2 wt.% clay nanocomposite shows complete exfoliation with respect to the shear force and residence time applied in this study, whereas, the addition of higher clay content produces ordered intercalated nanocomposite. It is of interest to mention that the compounding of Cloiste 30B (Southern Clay Products Inc.) in the same epoxy matrix and identical conditions shows complete exfoliation regardless of clay content [13]. This indicates that the degree of exfoliation depends on the type of clay and its surface modification. The TEM images of nanocomposites containing 1 and 10 wt.% of clay are presented in figures 3 and 4 respectively. The dark lines in figures 3b and 4b are the intersections of silicate layers of 1 nm thick. Both composites show intercalated structures with an average distance between two platelets of 3.6 nm and therefore, in good agreement with
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