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Unformatted text preview: cooperative movement when the polymer reaches its glass transition temperature. In general, more heavily crosslinked rubber leads to higher T g because the structure of three dimensional network hinders large scale chain movement. The T g of highly crosslinked materials can not be easily detected by DSC since the amount of heat exchange is small during the transition, but can be easily measured by DMA because DMA is 10 to 100 times more sensitive than DSC to the movement of polymer chains under dynamic bending mode (Menard 2008). Figure 2.4 shows the effects of various nanofillers on the storage modulus of FC2260 nanocomposites. Figure 2.4a compares the effects of the two types of clay on the modulus of the nanocomposites. The modulus plummeted at ca. -10 o C due to glass transition of the fluoroelastomer. The modulus increased with the...
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- Spring '08