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This work investigates and identifies the mechanisms that are at work in the creation of instabilities during co-injection moulding. Two aspects are investigated, neither of which has been previously reported. One seeks to eliminate the instabilities, the other to control them to produce mechanical interlocking of incompatible polymeric materials. Complex rheological and thermodynamic interactions take place during the co-injection moulding of materials of different generic families, which need to be understood before successful multi material mouldings can be achieved. Moulding trials on miscible, compatibilised and immiscible polymer systems were carried out to determine processing parameter effects. Analysis of tensile behaviour identified differences between injection moulding and co-injection moulding samples which are indicative of different heating and cooling regimes in the systems. Scanning electron microscopy analysis also assisted explanation of these effects. A previously unobserved bulk weakness in compatibilised systems was found. Surface profilometry was used to measure the size of disturbances at the wave fronts. The extent to which the interfacial instability occurs and to the material systems to which it applies was found. Instabilities were found or induced in all material systems investigated, including those where skin and core materials are the same. Mechanisms of instability at the melt front interface were determined and were found to be the result of stratification of elastic properties. Processing conditions were found to minimize instability by minimizing differences in elasticity at the interface. A novel process route using controlled instabilities was also proposed and investigated for the use of immiscible material systems. By controlling the moulding parameters, the potential problem of instability was used to provide a solution to bonding immiscible materials in co-injection mouldings without the use of compatibiliser.

Build-up is a fouling process in which a small fraction of a powder becomes a film adhered to a surface. Specifically buildup in auger fillers which is the focus of this thesis is a significant problem for industry leading to equipment downtime for cleaning, drives tripping due to high torque and reduced powder quality. The work presented in this thesis shows that for a unblended powder with a particle size similar to that of the auger fillers auger/tube clearance, build-up will be formed when powders have b-1 Kawakita parameter of less than 0.5 MPa and tablet strengths below 0.6 MPa post compression to 58 MPa. It is proposed based upon results the work of Crutchley and Bridgewater [29] and Calvert et al. [30] that powders which form build-up due so due to the stresses they experience as they pass through the auger/tube clearance. Additionally this stress is a function of the ratio of the powder’s particle size to the magnitude of the auger/tube clearance C. Work presented in Chapter 8 supports this conclusion showing that once C/D90 is greater than 3.5, build-up is not formed.

Electroactive, or 'conductive', polymers are a rapidly expanding area of research with proposed applications ranging from batteries or electronic circuitry to artificial muscles and actuators. An emerging application for these materials is as constituents of corrosion resistant coatings. An important factor in any corrosion resistant coating is the level of porosity it possesses. Minimisation of porosity may be highly desirable for the production of highly protective films. This work aims to study methods for controlling the porosity of polypyrrole films for their possible use as corrosion resistant coatings. It has been observed that surfactants can modify the structure and morphology of polypyrrole on inert substrates such as platinum or indium-tin oxide glass, and on the non-inert substrate mild steel. This has involved the study of the conditions necessary for polymer deposition on mild steel where the tendency for metal dissolution competes with the polymerisation reaction. Corrosion studies were carried out, firstly, to assess the corrosion potentials for such films and, secondly, via Tafel extrapolation to determine the effects of film thickness and anionic surfactant concentration on the corrosion rates obtained. Further corrosion studies were performed on polypyrrole films with additions of molybdate corrosion inhibitor species and anionic surfactants. It was found that polypyrrole with additions of anionic surfactants had little or no effect on the corrosion characteristics of mild steel in saline environments. However, in the presence of molybdate and certain levels of surfactants, excellent corrosion resistance characteristics were observed. It is proposed that the reduction of polypyrrole occurs at large negative corrosion potentials, resulting in the formation of an insulating polymer film that is incapable of acting as a site for displaced corrosion reactions around which many of the theories of electro active polymer corrosion protection have previously been based.

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A thermogravimetric technique for following lipase reaction kinetics has been developed. The relationships between the reaction rate and substrate have been determined for Candida Antarctica lipase B. At higher concentrations, evidence of substrate inhibition was found, due to the pH of the system decreasing as the concentration of acid increased. This has a dramatic adverse effect on the enzyme activity as it moves away from the optimum pH 7.0. Buffering the system closer to optimum pH increased the reaction rate. Also, it was found that as the hydrophobicity of the medium, expressed as C logP, increased the reaction rate became slower. The effect of substitution on the acid substrates was studied; it was found that the enzyme accepted substrates with substitution in the 3-position but not in the 2-position. As a result of modelling, this effect was explained by the disruption of hydrogen bonding, which stabilised the acyl enzyme tetrahedral intermediate. The thermodynamic reaction parameters were determined using Isothermal Titration Calorimetry. The difference in reactivity of ester and acid carbonyls was determined together with the entropy and enthalpy of formation of the acyl intermediates. In the solvent free reaction low dispersity and high molecular weight polyesters are formed due to the limited solubility of the polyester in the diol, only limited transesterification occurring at the ends of the chain. Molecular modelling was used to map the surface hydrophobicity around the enzyme active site in an attempt to explain the observed hydrophobic effects. Modelling around and within the active site was carried out in order to explain the activity of different substrates. The information gained from these studies led to the synthesis of several novel polyesters and polyurethanes, which may have commercial utility in coatings and adhesives. We have investigated the secondary structure of the Candida antarctica lipase B enzyme using conventional CD and synchrotron radiation CD in aqueous buffers and solvents. The secondary structure was determined under different conditions, using the CDSSTR and Selcon programs. Little difference was found between the structure in aqueous buffers and solvents such as hexane, however, really polar solvents like dioxane and THF unfolded the protein. Novel Near Infrared (NIR) spectroscopic methods were developed for the determination of the acid number and the hydroxyl number of polyesters. The effect of changes in the backbone structure of the polyester on the NIR spectrum of the polyester was determined and calibration curves developed for all the common types of linear aliphatic polyesters. The importance of the intra-molecular hydrogen bonding between the acid carbonyl and the hydroxyl groups has been established and the effect of temperature on the degree of association determined. It was found that even at a temperature of 120°C there was still substantial association between the two groups. Partial least squares analysis was developed for the simultaneous determination of both acid number and hydroxyl number. It has been shown that the principal difference between the conventionally synthesised polyesters and those synthesised using enzymatic catalysis is that the latter have little or no carboxyl termination at the ends of the polymer chain. This effect has been explained by the mechanism of the enzymatic polymerisation.

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The European Union (EU) Cosmetics Regulation established the ban on animal testing for cosmetics ingredients. This ban does not assume that all cosmetics ingredients are safe, but that the non-testing procedures (in vitro and in silico) have to be applied for their safety assessment. To this end, the SEURAT-1 cluster was funded by EU 7th Framework Programme and Cosmetics Europe. The COSMOS (Integrated In Silico Models for the Prediction of Human Repeated Dose Toxicity of COSMetics to Optimise Safety) project was initiated as one of the seven consortia of the cluster, with the purpose of facilitating the prediction of human repeated dose toxicity associated with exposure to cosmetics-related compounds through in silico approaches. A critical objective of COSMOS was to address the paucity of publicly available data for cosmetics ingredients and related chemicals. Therefore a database was established containing (i) an inventory of cosmetics ingredients and related structures; (ii) skin permeability/absorption data (route of exposure relevant to cosmetics); and (iii) repeated dose toxicity data. This thesis describes the process of “knowledge discovery from the data”, including collation of the content of the COSMOS database and its subsequent application for developing tools to support the prediction of repeated dose toxicity of cosmetics and related compounds. A rigorous strategy of curation and quality control of chemical records was applied in developing the database (as documented in the Standard Operating Procedure, chapter 2). The chemical space of the cosmetics-related compounds was compared to food-related compounds from the U.S. FDA CFSAN PAFA database using the novel approach combining the analysis of structural features (ToxPrint chemotypes) and physicochemical properties. The cosmetics- and food- specific structural classes related to particular use functions and manifested by distinct physicochemical properties were identified (chapter 3). The novel COSMOS Skin Permeability Database containing in vivo and in vitro skin permeability/absorption data was developed by integrating existing databases and enriching them with new data for cosmetics harvested from regulatory documents and scientific literature (chapter 4). Compounds with available data on human in vitro maximal flux (JMAX) were subsequently extracted from the developed database and analysed in terms of their structural features (ToxPrint chemotypes) and physicochemical properties. The profile of compounds exhibiting low or high skin permeability potential was determined. The results of this analysis can support rapid screening and classification of the compounds without experimental data (chapter 5). The new COSMOS oral repeated dose toxicity database was established through consolidation of existing data sources and harvesting new regulatory documents and scientific literature. The unique data structure of the COSMOS oRepeatToxDB allows capturing all toxicological effects observed at particular dose levels and sites, which are hierarchically differentiated as organs, tissues, and cells (chapter 6). Such design of this database enabled the development of liver toxicity ontology, followed by mechanistic mining of in vivo data (chapter 7). As a result, compounds associated with liver steatosis, steatohepatitis and fibrosis phenotypic effects were identified and further analysed. The probable mechanistic reasoning for toxicity (Peroxisome Proliferator-Activated Receptor gamma (PPAR ) activation) was formulated for two hepatotoxicants, namely 1,3-bis-(2,4-diaminophenoxy)-propane and piperonyl butoxide. Key outcomes of this thesis include an extensive curated database, Standard Operating Procedures, skin permeability potential classification rules, and the set of structural features associated with liver steatosis. Such knowledge is particularly important in the light of the 21st Century Toxicology (NRC, 2007) and the ongoing need to move away from animal toxicity testing to non-testing alternatives.