This thesis is concerned with the colour change and microstructural evolution of wet paint when subject of shear. When different processing shear histories are applied to certain paints, the resulting colour of the paint can vary. Paint consists of pigment particles suspended in a mixture of resin and solvent, and this multi-phase structure results in a complex microstructure. For this reason there can be many possible causes of this colour change, one of which was thought to relate to the organisation of the pigment dispersion. Rheological measurements of paint were carried out to investigate whether there was a link between rheology and colour change. The measurements were performed using a Rheometrics Dynamic Spectrometer (RDS II) at low shear rates and a Multi-Pass Rheometer (MPR) at high shear rates. Although the shear ranges of the RDS II and MPR did not overlap, extrapolation of data obtained at low shear rates matched those from the MPR at high shear rates. The rheological response of the material was described using a viscoelastic K-BKZ integral constitutive equation in combination with a Wagner damping factor. Systematic tests under controlled conditions were successfully performed, and the results of three paint samples were compared. The experimental findings indicated that the observed colour change behaviour of paint was related to the modification of size and size distribution of pigment agglomerates, both during and after shear. In order to correlate pigment size with the resulting paint colour, an attempt was made to model these experimental findings. A mathematical model was developed on the basis of the Mie scattering theory. This model was verified by a case study, and its prediction gave semi-quantitative agreement with the experimental findings.

Chapter 1 is a general and historical introduction to paint manufacture. Mention is made of a number of the polymerization methods used in paint manufacture and of the various uses to which different formulations of paint are used. Autoxidation and the factors controlling free radical reactions are also discussed. The overall aim of the thesis, the examination of the mechanism of autoxidation of allyloxy substrates is stated. In Chapter 2 examination of the radicals formed from the reaction of a number of monomeric model compounds with three different types of initiating radicals is discussed. By comparison with literature rate constants the position and type of radical attack is discussed. Thermal initiation of the radicals formed from the monomeric compounds is also examined. Chapter 3 examines the reaction of a number of polymers used in the preparation of a water-borne paint. The hardening process during the drying of a paint, both on the surface and sub-surface are also examined. From the results obtained in Chapter 2 the site of attack in the water-borne paint and related polymers is discussed. Chapter 4 examines the attempts to synthesise both an unsaturated bromoallyloxyether and an isotopically labelled alcohol or allyloxyether in order to further investigate the radicals which were detected by esr spectroscopy and spin trapping in Chapter 2 and 3.

This project is concerned with reactive dyes for dyeing cellulose (cotton) where reactive groups in the dye molecule form a covalent bond with hydroxyl groups in the cellulose chain by nucleophilic substitution or addition mechanisms. A fundamental problem is that the undesirable hydrolysis of the dye is a competing reaction under dyeing conditions and the hydrolysed dye is then no longer available for reaction with the fibre. The particular feature of interest is the chemical selectivity of the reactions of these dyes towards the fibre in preference to reaction with water and the factors which can influence these selectivities. In order to study the selectivities alone, without complications from the diffusion characteristics and substantivities of individual dyes, a homogeneous system was preferable for the investigations. So, a range of compounds were chosen as models to represent cellulose in these reactions. They covered simple alcohols, diols, polyols, and carbohydrate and sugar molecules - methanol, n-propanol, isopropanol, ethane-1,2-diol, α- and β-methylglucopyranoside, tetrahydropyran-2-methanol, mannitol, sorbitol, glucose and maltose. Using methanol as a cellulose model, the effects on rates and selectivities of varying the temperature between 0 and 60°C and additives to the dye bath such as acetonitrile, tetrabutylammonium bromide, urea, sodium chloride, sodium carbonate and dimethylformamide in a concentration of 100g/l have been investigated. Finally a survey of dyes with a wide range of reactive systems was carried out to determine whether selectivities are related to the reactive group that is used in the dyeing process. Reactive groups covered were : dichlorotriazine, monochlorotriazine, monofluorotriazine, chlorodifluoropyrimidine, dichloroquinoxaline, masked vinyl sulphones and acrylamides.

This Thesis describes the development and electrochemical testing of novel Zinc-Rich Paints (ZRPs) and coatings loaded with conducting polymers (specifically polyaniline) for use in the corrosion protection of steel, zinc and aluminium. Initial work concentrated on the development of model ZRPs using spherical and flake zinc powders dispersed in polyvinyl butyral (PVB). Both morphologies displayed a dramatic increase in through-film electrical conductance when the zinc volume fraction (Φ) reached the critical level (0.28) for long-range charge percolation. At the same level, these coatings sacrificially protect coated steel samples incorporating a defect. The duration of the protection increased with increased Zn volume fraction. The next phase of development saw carbon and a conducting polymer, Polyaniline Emeraldine-Salt (PAni-ES) used as "extenders" within a model ZRP organic coating. It was found that these systems fail to provide protection, despite "extending" charge percolation. This reflects the high level of cathodic activity on carbon itself and a chemical interaction between zinc and PAni-ES which rendered the coatings poor galvanic protectors. Only in instances with a high external cathode area (cut-edges) did the carbon "extended" coatings show acceptable performance. PAni-ES can protect iron and zinc surfaces in its own right. PAni-ES dispersions present in a PVB coating and solution-cast onto iron or zinc were shown to reduce rates of corrosion-driven cathodic disbondment. The presence of an adequate PAni-ES concentration also reduces the level of filiform corrosion on coated aluminium (AA2024-T3) substrates. The PAni-ES works on metal substrates by a combination of (a) raising the surface potential, (b) forming an oxide layer and (c) buffering under-film pH. The ZRPs have been developed into a system close to commercial applicability for the production of domestic appliances and from the data obtained to-date PAni-ES seems appropriate for the protection of a range of metals, as a replacement for the toxic and carcinogenic chromate systems currently in use.

This project is primarily concerned with the reactions of halotriazine reactive dyes for cellulose, in aqueous solution. The effect of small amounts of added alcohol (~ 0.05M) on the rates of hydrolysis of a dichlorotriazine dye has been analysed by study of the individual contributions towards rate, of the concurrent alcoholysis and hydrolysis reactions. Kinetics and products studies were all carried out using ion-pair reverse-phase HPLC. Of the alcohols studied; methanol, ethane-1,2-diol and propargyl alcohol, provided rate-product correlations; whilst α- and β-methylglucopyranoside, mannitol, sorbitol and trifluoroethanol all produced rate enhancements of hydrolysis in the region of 10-50%. Medium effects of the added alcohols were found to be negligible and most likely explanation of the rate enhancements has been proposed to be the presence of a third-order, alkoxide-assisted mechanism for hydrolysis. The viability of this proposal was investigated using Bronsted and KSIE analysis. Bronsted plots for second order alcoholyses and third order hydrolyses are linear, with plausible slopes, with the exception of hydroxide which exhibits a 100-fold negative deviation in all cases. Furthermore, significant evidence exists that the hydrolysis of the dye also undergoes a hydroxide-assisted mechanism, analogous to that observed in the presence of alkoxides. Salt effects on the reactions of these dyes were found to be substantial; Five-fold rate enhancements were observed in the presence of ~ 0.1M sodium sulfate, sodium carbonate and some tetraalkylammonium salts. Hence, no buffer catalysis could be observed. Method development of HPLC and HPLC-MS analysis of sulfonated dyes and their reaction products has been optimised. Finally, a survey of homogeneous chemistry of compounds containing a dinitrofluorobenzene reactive group was carried out. Model compounds were synthesised, on which rate and product studies were conducted in aqueous and methanolic solution.

Due to its ubiquitous presence in paints of all colours, titanium dioxide represents the primary pigment used in Organically Coated Steel (OCS) for construction applications. However the semi-conducting nature of TiO<SUB>2</SUB> translates into a possibility of inducing photodegradation when exposed to Ultra Violet (UV) radiation such as that present in sunlight. Initial research concentrated on developing a test procedure of the photoactivity of these pigments within a PVC binder. Model coatings, using pigments of known performance, have been tested to evaluate the success of this rapid test technique and excellent correlation has been shown. Building on this, Chapter 4 details a unique cell that has been designed, constructed and tested resulting in a more versatile testing environment. This cell has been used to examine the photostability of 4 commercially available pigments while present within a standard emulsion paint binder. Chapters 5 and 6 detail work performed on Plasticised PVC paint films and the resultant effects this has on the kinetics of photodegradation as monitored via the evolution of CO<SUB>2</SUB>. Also incorporated into this design is the ability to identify and quantify volatile organic components that are evolved during the degradation process, thus providing information regarding the photodegradation mechanism occurring within the film. It has been found that in these model films, the addition of plasticiser increases the rate of photogenerated CO<SUB>2</SUB> and also produces volatile components that can be directly related to the parent plasticiser molecule. There is some evidence to suggest that for certain plasticisers, a sacrificial protection mechanism is at work, resulting in increased CO<SUB>2</SUB> evolution but decreased attack on the binder matrix. Finally in Chapter 7, a number of complimentary techniques are employed to assess the effect that TiO<SUB>2 </SUB>photocatalysed PVC degradation has on the underlying substrate material. The techniques include electrochemical impedance spectroscopy (EIS), electro-generated chemiluminescence (ECL) and 3-D scanning vibrating electrode technique (3-D SVET). Photodegradation leads to porosity development in coatings and eventual through coating penetrative defects lead to corrosion.

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