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The main objective of this work, which was the synthesis of water-soluble polymers for scale formation inhibition on stainless steel surfaces, has been achieved. Following an introduction and discussion of the background of the work (Chapter 1), the synthesis and characterisation of various monomers, norbomenes with alkylene ether side chains terminated by trialkyl ammonium salts, is described (Chapter 2). These monomers were polymerised to give water-soluble materials, as described in Chapter 3. The nature of the polymers involved and the development of special techniques for their characterisation is explained in Chapter 4. The amphiphilic water-soluble polymers prepared were used as additives in a detergent solution for scale inhibition tests. The variation in the structures of the polymers prepared allowed the study of the effects of different factors on scale inhibition, including the molecular weights of the polymers, the lengths of the alkylene ether side chains, and the nature of the trialkyl ammonium salt functionality. Most of the materials synthesised had an inhibiting effect on scale formation on the stainless steel substrate, in that treated surfaces allowed an easier cleaning of the samples. This study allowed the identification of a polymer structure showing good properties for scale inhibition, which may provide a lead for future development.

A wide range of polymer film products are available with varying degrees of permeability to a variety of gases, from oxygen to water to aromatic species. The barrier properties are determined primarily by the choice of the matrix polymer, and fine tailoring can be introduced through the addition of filler materials such as inorganic platelets and polymer blend materials. It was identified that hollow and porous addition of such particles appears little studied. Gel particles were prepared by free radical emulsion polymerisation of styrene and DVB in presence of hydrophobic solvents. Porous particles were prepared by the surfactant free emulsion copolymerisation of VBC and DVB, followed by Friedel- Crafts alkylation to yield hypercrosslinked microporous nanoparticles. Porous and gel particles were added to polymer films and the oxygen permeability and mechanical properties of these films determined. It was found that the addition of hypercrosslinked microporous nanoparticles increased the oxygen permeability of the films up to 〜50 % when added at 40 wt% loading. Further to these studies, hollow nanoparticles were prepared by the emulsion phase ATRP of DVB when initiated by mPEG-6-PS inisurf in the presence of a hydrophobic solvent.

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In this study polypropylene was modified by a range of talc (Mg3(OH)2Si4OlO) fillers. Three different types of surface modifiers were also used, two types of silanes (octyltriethoxysilane and y-aminopropyltriethoxysilane) and maleic anhydride modified polypropylene plus polyethylene wax as an external lubricant. A series of compounds were prepared in an APV twin screw compounder, based on talc addition level, morphology, particle size, surface coatings and coupling agents. The study showed that addition of talc to PP increases the shear viscosity and the blend system generally follows the power law in the shear rate range studied. The experimental values obtained with talc-filled PP were compared with theoretical data obtained from the Maron-Pierce type equation. It was found that theory predicts a higher value of relative viscosity for some talc fillers. A model equation is proposed for talc-filled PP that predicts accurately relative viscosity of the compound for different volume fractions of talc filler. PP-filled with talc having predominantly acicular particles (high surface area), shows a highest shear viscosity values, since high surface area fillers tend to increase the occluded polymer increasing the effective filler volume. The addition of a high level of coating decreasess hearv iscosity of the system,a ddition of a reactivec oupling systems lightly increasess hearv iscosity. Wall slip for unfilled PP was consistently evident. The slip velocity increases systematically with shear stress, but there is a critical value below which slip velocity was negligible. Addition of talc decreased the slip velocity at a given stress. A mechanism of slip has been proposed whereby a 'slip layer' on the die surface provides a sharp, low energy interface over which, at sufficiently high shear stress, the fluid PP can slip. A new empirical model has been proposed to predict the slip velocity of filled PP, as a function of talc volume fraction. PP filled with 10 % wt. talc having predominantly acicular particles, showed a higher slip velocity than PP filled with talc of other morphologies. It was observed that slip velocity increased by coating talc (either by use of coating or coupling agents) due to modification of velocity distributions in the flow channel. Extrudate swell increases with increasing shear rate for unfilled and talc-filled PP compounds. Inclusion of talc generally decreases the swell over the entire range of shearr ates studied,b ecauset he addition of talc to PP increasesth e shear/extensional modulus and thereby decreasede lastic strain recovery. No appreciablei nfluence of particle size on swell ratio was observed. Coating talc with octyltriethoxysilane produces higher swell relative to uncoated filled PP, and higher coating levels consistently produced higher swell values. However, coupling agent 7- aminopropyltriethoxsilane and maleic anhydride modified polypropylene both reduced the swell of the filled polymer system, with a more pronounced effect in extension than in shear. Swell decreased with an increase in capillary length-todiameter ratio and increased with increase in shear rate, (or shear stress) with or without coating/coupling agent. Addition of talc fillers delayed the onset of melt fracture and higher loadings of talc completely suppressed the melt fracture in the range of shear rate studied. Melt fracture for unfilled and filled PP has been studied and quantified by the frequency of the melt distortion. A mechanism for polymer melt fracture has been proposed to explain the results, based on the tensile failure of the material in extensional deformation. It was found that shear rate and die L/D ratio were the major causes of changesin severity of melt fracture for the unfilled and talc-filled compoundss tudied. However, talc morphology and particle size did not have significant effects on the severity of melt fracture.

An investigation is undertaken into the dynamics of phase separation in polymer blends in order to try to understand the morphologies produced via spinodal decomposition and to identify ways to target beneficial morphologies. Cahn-Hilliard theory is used with the Flory-Huggins free energy to model phase separating systems undergoing spinodal decomposition for a number of different systems. Initially a simple two component blend is studied undergoing spinodal decomposition via a temperature quench from the one phase to the two-phase region. The model is then used to study the process of secondary phase separation via a two-step quench process. A temperature quench from the one phase to the two phase region is undertaken and then the system is left to equilibrate for two different time periods before a quench further into the two phase region is carried out. The model is then extended to focus on the technologically useful process of reaction induced phase separation. In this case a two component polydisperse blend is quenched from the one phase to the two phase region via polymerisation of one component of the blend. The phase separation process is followed for selected reaction rates and the consequences of changing the final degree of polymerisation are studied both with and without the formation of a network in the reacting component of the blend. Finally a study of the effect of adding a surface into the blend is undertaken to show the development of a phase separated morphology at and near to the surface, we also present a method to overcome inconsistencies found in the Cahn-Hilliard model. The model is then used to target specific phase separated morphologies on a chemically patterned surface and to try and understand the processes involved in the phase separation of a three component, A B C, blend at a surface.

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