Applications of ft-infrared spectroscopy and ft-Raman spectroscopy as analytical tools

Abstract

Infrared spectroscopy and Raman spectroscopy are invaluable analytical techniques used for a wide range of applications. The simple and versatile nature of the techniques provides analytical scientists with methods to determine parameters such as the identification of molecules and studies of crystallinity.
The work presented in this thesis is concerned with the use of firstly, infrared spectroscopy to study the polysulfide sealants currently used in the aerospace industry, and secondly, the use of Raman spectroscopy to study the polymers polypropylene and poly(ethylene terephthalate) at high temperatures.
Chapters 3 and 4 deal with the study of the degradation of polysulfide sealants. The fact that vibrational spectroscopy is a standard method of analysing degradation products and processes is emphasised. Polysulfide sealants as used in the aerospace industry, degrade over their lifetime resulting in costly repairs. In chapter 3 the chemistry of polysulfides and the factors, such as pretreatment of the adherend, which affect adhesion are introduced. Evidence is provided of cutting fluids remaining on the adherend after methods used to remove such fluids have been applied. An understanding of the degradation process in polysulfide sealants will lead to a better understanding of how to improve the sealants in the future. Chapter 4 puts forward a method for accelerating degradation testing of sealants.
Chapter 5 reports the first FT-Raman spectra of the polymers polypropylene and poly(ethylene terephthalate) above 200 °C. Observation of regularity bands and short range order at temperatures above the melting points lends credence to the arguments for a mesomorphic phase in the polymers.

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