Date of Award
Summer 1996
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Wilkie, Charles A.
Second Advisor
Bloch, Daniel R.
Third Advisor
Donaldson, William A.
Abstract
Section 1. For a long time people have believed that graft copolymerization has occurred on poly(ethylene terephthalate), PET, fibers and the proof of this has typically been showing that the surface properties of the polymer had been modified in some way. From this research, it has been shown that no grafting occurs onto PET for a radical initiated process. Several monomers and initiation systems were studied and in all cases the two components can be separated by dissolution process. The surface properties are modified because homopolymerization of the vinyl monomer occurs within the PET film and this is retained within the film. The two polymers form a entangled structure which prevents isolation by simple solubility test.
Section 2. Polystyrene is a chemically stable polymer but it is not very thermal stabile. The goal of this section of the work was to introduce a char-forming monomer, such as acrylonitrile, onto the polystyrene in order to enhance the char forming ability of the polystyrene. Radical initiators are not effective for the graft copolymerization of acrylonitrile onto polystyrene but an anionic process, using butyllithium as the initiator, does enable the reaction. The lithiation of polystyrene occurs on the aromatic ring and the addition of acrylonitrile leads to enhanced char formation when the graft copolymer is thermolyzed.
Section 3. Degradation of polyacrylonitrile involves cyclization of adjacent monomer units and the elimination of ammonia and hydrogen cyanide but the order and pathway of these reactions is not understood. The TGA/FTIR technique has been used to identify the evolved gases and the solids which remain are identified by infrared spectroscopy and elemental analysis. It is shown that the evolved gas phase mainly consists of ammonia, HCN and methane. Cyclization is the initial reaction and this is followed by the loss of ammonia, hydrogen cyanide and methane. Schemes are proposed to account for the formation of ammonia and hydrogen cyanide.