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possible to reveal very specific thermomechanical information about a material,
ranging from basic stress-strain behavior to subtle thermal transitions which occur
in the polymer and may be very difficult if at all possible to observe through
microscopy or spectroscopy.
Due to the height limitations of the available A-CNTs which can be grown,
compression remains the Onlyviable method for this type of testing. The high
compliancy of PDMS allows for the compression of these composites to high strains
dynamically, making DMA relatively straightforward, as explained in Figure 3.4.
Another benefit of using PDMS is the ease of sample preparation. PDMS can be very
easily cut by using a razor blade and a steady hand, and for all of the following data,
samples measuring 2.5 mm long x 1 mm wide x 1 mm tall were used. Due to the
anisotropicity of the CNTs in these samples, they can be tested in two particular
orientations: 1) longitudinal to the alignment of the CNTs (axial), or 2) transverse to
the alignment of the CNTs (radial); a schematic of the particular orientations as
compared to the neat polymer and a SEM image of a sample can be seen in Figure
3.5.
Over the next few sections, I will discuss the fundamental dynamic
mechanical properties as observed through DMA, and the information revealed by
these tests as compared to the properties of the neat polymer.