An investigation of the photoinitiated cationic cross-linking polymerization of some epoxy resins
As well as dealing with general topics pertinent to the project, the first chapter gives the aims of the project and reviews the theories of network formation. Particular attention is paid to the occurrence of inhomogeneous cross-linking in nonlinear chain-growth polymerizations. The second chapter reviews an important aspect of photoinitiated polymerizations, namely the photochemistry of the photoinitiator used, in this case diphenyliodonium hexafluorophosphate. The preparation and characterization of the photoinitiator and the characterization of the commercial monomers are given in chapter three. The fourth chapter reports an investigation of the effect of various parameters on the decree of cross-linking as determined by a variety of techniques. The results can be interpreted in terms of inhomogeneous cross-linking and show that irradiation combined with thermal treatment produces the highest degree of cross-linking. Chapter five deals with a study of the photo-oxidative stability of two of the photocurable resin systems. Certain monomer systems were found to exhibit a transient colouration on cure and chapter six gives a possible explanation for this effect as well as the results of experiments designed to provide additional verification. Finally, chapter seven reports the outcome of attempts to obtain low surface free energy films by the addition of small amounts of polyfluorinated monoepoxides to the conventional monomers in the hope that surface segregation of the fluorinated material would occur in the interval between application and cure of films.