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Polymer00045 - including a initial curing stage for 7-20...

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34 The dispersion of the nanofillers and the morphology of the fluoroelastomer nanocomposites were studied by a transmission electron microscope (TEM) (JEOL 1200EX) operating at 100 kV. Thin slices (80-100 nm) of the samples were cut using an ultramicrotome (Powertome X, Boeckeler Instrument) at -50 o C. The thin slices floated in alcohol after cutting and were collected using TEM copper grids. The cryo-sliced surface was also examined by Field Emission Scanning Electron Microscopy (FE SEM, Quanta 200F) to investigate the morphology of fluoroelastomer nanocomposites. In order to better understand the phase structures of the composites, samples were also cryo- fractured in liquid nitrogen and the fracture surfaces were examined by FE SEM. 2.4 Results and Discussion 2.4.1 Factors Influencing Curing Behaviors of Fluoroelastomer Nanocomposites The fluoroelastomer FC2260 used in this study has a two-stage curing process
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Unformatted text preview: including a initial curing stage for 7-20 minutes at 177 o C and a post curing stage for 20-24 h at 242 o C. Figure 2.2 compares the Haake mixing torque of the different FC2260 nanocomposites during the initial curing stage. The mixing torque decreased rapidly and gradually leveled off as the elastomer was melted and mixed with the nanofillers toward higher homogeneity. The crosslinking agent was added after three minutes of mixing, and the mixing torque increased significantly, indicating the occurrence of the elastomer crosslinking. Figure 2.2 (a) shows that, before adding the crosslinking agent, the higher the treated silica (T-SiO 2 ) content, the larger the mixing torque. This was due to the viscosity increase of the elastomer caused by the added nanofiller. Before the curing agent was added, the difference in mixing torque between samples containing 0, 2, and...
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