Thermal stability of polymers: Relation to cross-linking and nanocomposite formation

The focus of this research has been on the effect of cross-linking and nanocomposite formation on the thermal stability of polymers. Chapter I gives a brief introduction on the processes occurring during degradation and test methods used to determine thermal stability of polymers. Research on cross-linking of polymers is presented in Chapters II and III. Chapter II examines the effect of cross-linking on thermal stability of polybutadiene while Chapter III examines cross-linking of poly(methyl methacrylate) and polystyrene. From this work and previous work it has been shown that it is the size and type of cross-link that is important for enhanced thermal stability rather than the number of cross-links. Thanks are extended to G. F. Levchik and S. V. Levchik for obtaining the TGA and DSC data and mechanistic input in the work done in Chapter III and to C. Dick, J. J. Liggat, and C. E. Snape for doing solid state NMR on these cross-linked polymers. Chapters IV through VII examine the effect of nanocomposite formation on thermal stability of polymers. In particular graphite nanocomposites where the type of graphite used is in the following forms; potassium graphite (Chapter IV), expandable graphite (Chapters V and VI), and modified graphite oxides (Chapter VII). The research presented here shows that graphite-nanocomposites behave similarly to clay-nanocomposites in that a reduction in PHRR is observed and thermal stability is similar. There does appear to be a difference in the time to ignition for graphite-nanocomposites and the mechanical properties are not enhanced as one might have expected. Thanks is given to Qiang (John) Yao who preformed the dynamic mechanical testing (DMA) on these nanocomposites