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Polymer00048 - Ea continuously decreased with increasing...

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37 2.4.2 Vulcanization Kinetics during Post Cure Study of vulcanization kinetics of FC 2260 and its nanocomposites was performed on the Haake rheometer premixed materials using DSC. Non-isothermal curing in DSC was carried out from 30 to 350 o C at the heating rates of 8, 10, 15, and 20 o C/min, respectively. Activation energy of the vulcanization was calculated using the Kissinger’s equation. Figure 2.3 shows ln(q/T p 2 ) versus 1/T p for the samples comprising treated silica and graphite. According to the equation, -ln(q/T p 2 ) versus 1/T p yields a linear relationship and the activation energy Ea, which is related to the mechanism of the curing process, is obtained from the slope of the ln(q/T p 2 ) versus 1/T p line. Large slope means high activation energy and high resistance to the cultivation process. The values of Ea for all the samples are given in Table 2. As shown in Figure 2.3a, the addition of treated silica (T-SiO 2 ) reduced Ea of the neat FC 2260.
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Unformatted text preview: Ea continuously decreased with increasing T-SiO 2 content, indicating that the treated silica facilitated the vulcanization of the fluoroelastomer. FC 2660 comprising 4% T-SiO 2 displayed the lowest activation energy (32.6 KJ/mol) among all the samples, which is in agreement with the results obtained from Haake mixing where FC 2660/ 4% T-SiO 2 exhibited the highest mixing torque. The promotion of the fluoroelastomer vulcanization by the T-SiO 2 is explained by its function as a secondary crosslinking agent. T-SiO 2 reduces the activation energy of neat FC 2660 from 81.0 kJ/mol to 65.1 and 32.6 kJ/mol for 2 and 4% T-SiO 2 , respectively (Table 2). In comparison, 2 and 4% untreated silica reduced the activation energy to 72.3 and 67.8 kJ/mol, respectively. The higher activation energy of the T-SiO 2 composites (especially at 4% nanofiller content) again proved the crosslinking effect of the silane coupling agent....
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