Part I. The fire properties of polymer clay nanocomposites. Part II. Thermal rearrangement of donor-acceptor substituted cyclopropanes
Abstract
This work consists of two parts. Part I, which includes chapter 1-5, is focused on the fire properties of nanocomposites while part II deals with thermal rearrangement of the donor-acceptor cyclopropanes. In chapter 1 of the first part an introduction to the preparation of polymer-clay nanocomposites is provided along with their application to fire retardancy. Chapter 2 details the exfoliation process of clay using in situ polymerization; the results show that the exfoliation process is related to the monomer, the modified clay and the initiator. Chapter 3 concentrates on the preparation of nanocomposites by melt blending with polymer modified clays. Three different polymer modified clays (PS, PMMA and PBD modified clay) and six polymers (PS, HIPS, ABS, PMMA, PP and PE) are reported. The morphology, thermal stability, fire behavior and mechanical properties were studied. This research shows that the exfoliation process by melt blending is controlled by the types of interactions between the various polymers, the silicate surfaces and the organic modifier. The combination of polar polymer matrix and non-polar polymer modified clay with large d-spacing will be more likely to give the exfoliated nanocomposites. TGA-FTIR results show that the mechanism of degradation of polystyrene is changed in the presence of the clay. In order to better understand the effects of the organic modifier, PS surfactants with five different pendant groups, dimethylhexadecylamine, trimethylamine, dimethylbenzylamine, 1,2-dimethylimidizole and triphenylphosphine, were used and the results show that the degradation depends upon the pendant. Chapter 5 provides some suggestions for future work based upon this work. The synthesis of several new and previously reported donor-acceptor cyclopropanes is reported in part II. The study shows that the facility of the donor-acceptor cyclopropane ring cleavage is strongly influenced by the kind of activating substitutes on the cyclopropane ring, and the stability of the functional groups is relative to the pKR⊕ and pKa values. Mechanistic study involving the thermal rearrangement of the donor-acceptor substituted cyclopropanes is also reported.
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