Thermal Resistance of CW-FA Nanocomposites

Reprinted with permission from Macromokcuks 2008, 41 (22), 8682-8687. Copyright 2008, American Chemical Society). 

In CW-PFA, the onset of degradation (temperature at 5% weight loss) is at 323 °C, which is 77 °C higher compared to y-Al-PFA, and remarkably, also 20-30 C higher compared to the MMT-PFA nanocomposites. The residual weight of CW-PFA is 6wt% (units) higher at 500°C and 4wt% (units) higher at 800 C compared to pure PFA. Table 6.2 summarizes the main TGA results. 

This section discusses the results of reactive molding of nanocomposites from naturally occurring MMT clay. This was achieved by in-situ polymerization, using FA as a polymerizable solvent medium to produce MMT-PFA nanocomposites. 

Surface-modified MMT clay is commercially available, as well as natural sodium MMT. Since FA is hydrophilic, in contrast to the hydrophobic PFA, the intercalation process was studied both with naturally occurring hydrophilic sodium MMT (NaMMT) and with an organomodified MMT (30BMMT), which is hydrophobic. 

To characterize the polymerization behavior of FA and to investigate how the presence of MMT influences this polymerization, FTIR spectra were collected before and during the resiniflcation process. The dispersion of the MMT in the PFA matrix is shown both directly and indirectly. The direct evidence consists of the XRD patterns of the FA-MMT suspension, which was used to monitor the process of intercalation and exfoliation of the MMT at various stages of resinifica-tion. The dispersion is indirectly evidenced in increased thermal stability of the MMT-PFA nanocomposite, as measured by TGA. The thermal stability is discussed and compared to the pure polymer and to the CW-PFA nanocomposites. In addition, the important differences between oxidative and nonoxidative degradation of the NaMMT-PFA nanocomposite is discussed, and a mechanism is proposed to explain the difference in terms of acid-catalyzed degradation. 

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