Four sets of NIPAM and non-NIPAM based colloidal microgels have been synthesized by a surfactant-free emulsion polymerisation (SFEP) technique, which are: (i) poly (NIPAM) based homo-polymer, (ii) poly (NIPAM) based co-polymer, (iii) hydrophobically modified homo-polymer and (iv) hydrophobically modified co-polymer microgels. Poly (NIPAM) based homo-polymer microgels have been studied with respect to their heteroaggregation/heteroflocculation behaviour with oppositely charged polystyrene latex (PS) particles. It has been shown that the particle size, concentration and temperature play an important role in the ionic interaction between oppositely charged microgel and PS latex particles. Some particulate dispersions have shown temperature-dependent reversible flocculation behaviour, which could be applicable in the water industry for the removal of colloidal impurity from water. A strong irreversible aggregation was also observed for some microgel-latex mixtures, which may find useful application in the field of crude oil recovery. Hydrophobically modified homo-polymer and co-polymer microgels have been prepared from a range of novel monomers. The monomers have been chosen with varying hydrophobic chain length in order to manipulate the swelling properties of the resultant particles in different solvents. The dispersibility behaviour of the novel and NIPAM-based microgels has also been studied in different solvents to find their utility in removing water from oil. Colloidal microgel particles have shown successful application in reducing the water content of biodiesel to an acceptable level. Karl Fischer titration results have shown that water level in biodiesel can be reduced below 500 ppm from 1800 ppm by using microgel as water absorbent. According to the EN14214 specification by European Committee 500 ppm is the maximum water level allowed in biodiesel to be useful in combustion engine.

The deposition efficiencies of a number of electroless nickel and cobalt plating solutions were studied and in the case of nickel compared with a commercial plating solution Nifoss 80. At the optimum plating conditions (92ºC and pH 4.5) Nifoss 80 produced nickel layers most efficiently, the alkaline cobalt solution operated most efficiently at 90ºC and pH 9. The methods of producing compostte layers containing 2-3 µm carbide particles and chromium powder is described. Nickel and cobalt layers containing approximately 27% carbide particles, or 40% (Ni) and 30% (Co) chromium particles by volume were obtained. This value is independent of the particle concentration in the plating solution within the range (20~200 g/l). Hardness of the nickel. as deposited was 515 Hv, this was increased to a maximum of 1155 Hv by heat treatment at 200ºC for 5 hours in vacuum. Incorporation. of .chromium carbide particles resulted in a maximum hardness of 1225 Hv after heating at 500ºC for 5 hours in vacuum and chromium particles resulted in a maximum hardness of 16S0 Hv after heat treatment at 400ºC for 2 hours in vacuum. Similarly the hardness of cobalt as deposited was 600 Hv, this was increased to a maximum of 1300 Hv after heat treatment at 400ºC for 1 hour. Incorporation of chromium carbide particles resulted jn a maximum hardness of 1405 Hv after heating at 400ºC for 5 hours in vacuum and chromium particles resulted in a maximum hardness of 1440 Hv after. heat treating for 2 hours at 400ºC in vacuum. The structure of the deposits was studied by optical and scanning electron microscopy. The wear rate and coefficient of friction was determined by a pin and disc method. Wear rate and coefficient of friction decreased with increase in hardness. The wear resistance of the materials was also determined using a simulated forging test. Dies made of standard die steel were coated and the wear rates of the layers as deposited and after heat treatment were compared with those of uncoated tools. The wear resistance generally increased with hardness, it was 50-75% more than the uncoated die steel. Acetic acid salt spray test and outdoor exposure for six months was used to study the corrosion behaviour of the deposits and potentiodynamic curves plotted to find their corrosion potential. Nickel deposit exhibited less staining than carbide composite deposits and nickel-chromium deposits had the most noble corrosion potential.

This thesis considers the computer simulation of moist agglomerate collisions using the discrete element method (DEM). The study is confined to pendular state moist agglomerates, at which liquid is presented as either absorbed immobile films or pendular liquid bridges and the interparticle force is modelled as the adhesive contact force and interstitial liquid bridge force. Algorithms used to model the contact force due to surface adhesion, tangential friction and particle deformation have been derived by other researchers and are briefly described in the thesis. A theoretical study of the pendular liquid bridge force between spherical particles has been made and the algorithms for the modelling of the pendular liquid bridge force between spherical particles have been developed and incorporated into the Aston version of the DEM program TRUBAL. It has been found that, for static liquid bridges, the more explicit criterion for specifying the stable solution and critical separation is provided by the total free energy. The critical separation is given by the cube root of liquid bridge volume to a good approximation and the 'gorge method' of evaluation based on the toroidal approximation leads to errors in the calculated force of less than 10%. Three dimensional computer simulations of an agglomerate impacting orthogonally with a wall are reported. The results demonstrate the effectiveness of adding viscous binder to prevent attrition, a common practice in process engineering. Results of simulated agglomerate-agglomerate collisions show that, for colinear agglomerate impacts, there is an optimum velocity which results in a near spherical shape of the coalesced agglomerate and, hence, minimises attrition due to subsequent collisions. The relationship between the optimum impact velocity and the liquid viscosity and surface tension is illustrated. The effect of varying the angle of impact on the coalescence/attrition behaviour is also reported. (DX 187, 340).

Polymer modified cements and mortars have become popular for use as patch repair materials. General evidence suggests that these materials offer considerable improvements compared to traditional mortars although the mechanisms for this are not fully understood. This work elucidates the factors which govern some properties and performance of different polymer systems. In view of the wide range of commercial systems available, investigations concentrated on the use of three of the most commonly available groups of polymers. These were: (1) Styrene Butadiene Rubber (SBR), (2) Acrylics and, (3) Ethylene Vinyl Acetates (EVA). The later two were in the form of both emulsions and redispersible powders. Experiments concentrated on: (1) Rheological behaviour of polymer modified cement pastes; (2) Workability of polymer modified mortars; (3) Influence of curing conditions on the pore size distribution and diffusion of chloride ions; (4) Bond strength of polymer modified cement and mortar patches; and (5) Microscopic examination and semi-quantitative analyses of the bulk and interfacial microstructures. The following main conclusions were reached: (1) The addition of polymer emulsions have a considerable influence on the workability of fresh cement pastes, the extent of this depending on the type of system used. (2) The rheological parameters of fresh polymer modified mortars can be established using a two-point workability test which may be used when comparing the properties of different systems at constant workability. (3) Curing conditions affect the properties of polymer modified systems and a wet/dry curing regime was essential for good adhesion of these materials to mortar substrates. (4) In contrast, the wet/dry curing regime resulted in a curing affected zone at the surface of patch materials. This can result in a much coarser pore structure and enhanced diffusion of e.g. chloride ions. (5) The microstructure of polymer modified systems was very different compared with the unmodified cement/mortar and varied depending on curing conditions.

Investigations concentrated on the styrene butadiene rubber (SBR) latex and formulations included standard carboxylated and special carboxylated latexes. The aqueous component, containing the stabilisers and antifoaming agent but not the polymer solids, was also used. For comparison, limited investigations were carried out using other polymer types e.g. acrylic, ethylene-vinyl acetate (EVA), and redispersible powders rather than emulsions. The major findings were: 1) All latex systems investigated acted as retarders for cement hydration. The extent of retardation depends on the type of polymer. The mechanism for cement hydration may be changed, and excessive retardation influences properties. 2) Polymer modified cements exhibited either similar or coarser pore structures compared with unmodified cements. Results suggest that polymer mainly exists in a mixture of cement hydrates and polymer phase. Very little evidence was found for the formation of a distinct polymer film phase. 3) During the first few days of curing the polymer solids are removed from the pore solution and concentrations of OH-, Na+ and K+ are reduced. These observations are probably a result of polymer-cement surface interactions since there was no evidence of any chemical reactions or degradation of the polymer. 4) Improved diffusional resistance of modified cements depends on the ability to achieve adequate workability at low w/c ratio, rather than modification of matrix structure.

A laboratory study was undertaken featuring a selection of minestones from several British coalfields. The stability of minestone and CSM in sea water and distilled water was assessed using slaking tests and immersion monitoring and the bearing on the use of these materials for hydraulic construction is discussed. Following a review of current erosion apparatus, the erosion/abrasion test and rotating cylinder device were chosen and employed to assess the erosion resistance of minestone and CSM. Comparison was made with a sand mix designed to represent a dredged sand, the more traditional, bulk hydraulic construction material. The results of the erosion study suggest that both minestone and CSM were more resistant to erosion and abrasion than equivalently treated sand mixes. The greater resistance of minestone to the agents of erosion and abrasion is attributed to several factors including the size of the particles, a greater degree of cement bonding and the ability of the minestone aggregate to absorb, rather than transmit shock waves produced by impacting abrasive particles. Although minestone is shown to be highly unstable when subjected to cyclic changes in its moisture content, the study suggests that even in an intertidal regime where cyclic immersion does takes place, minestone will retain sufficient moisture within its fabric to prevent slaking from taking place. The slaking study reveals a close relationship between slaking susceptibility and total pore surface area as revealed by porosimetry. The immersion study shows that although the fabric of CSM is rapidly attacked in sea water, a high degree of the disruption is associated with the edges and corners of samples (ie. free surface) while the integrity of the internal fabric remains relatively intact. CSM samples were shown to be resilient when subjected to immersion in distilled water.

No description available.

The synthesis, stability and properties of two particular processible conducting polymer types, polyaniline and polythiothene have been investigated. Those two classes of polymers have great commercial potential but their properties can be difficult to control. Polythiophene was evaluated as potentially useful in a photolithographic process. When polymers are involved in image formation, changing the solubility of the exposed polymer is usually required. Photodegradation was chosen as a way to render crosslinked polythiophene soluble. The photodegradation study was divided in two parts; in solution and in the solid state. Methylene blue was used in both cases as a generator of singlet oxygen. The polymer effectively underwent photodegradation under irradiation at 670nm. It could not be determined from our studies whether this effect was due to methylene blue or spontaneous photodecomposition of the polymer itself. This line of work was then discontinued and we focused on the polyanilines. The synthesis of various polymers of the polyaniline family was performed and different modes of polymerisation evaluated. In particular the parameters of the emulsion polymerisation of PANI-DBSA (dodecylbenzene sulfonic acid doped polyaniline) were evaluated and a new process was formulated. The doping on heating of polyaniline base (EB) with two dopants DBSA and toluene sulfonic acid (TSA) was studied using differential scanning calorimetry (DSC). Polymers with a molar ratio of base unit/dopant of 1 presented the good thermal stability and solubility expected from sulfonic acid doped polyanilines. The conductivity of the samples obtained was up to 15 Scm[sup]-1 and was improved by annealing polymer films, which led to conductivities of up to 25 Scm[sup]-1. Finally, a comprehensive study of the thermal stability of the various polyanilines produced is presented. The good stability of polyaniline was demonstrated by DSC and thermogravimetric (TGA) studies. The initial degradation stages were allocated to the loss or decomposition of dopants. Some degradation products were identified by gas chromatography coupled with mass spectrometry (GC-MS) and correlate with loss and decomposition of the dopants. The kinetic parameters of the decomposition of the polymers were calculated using a computer package and a tailored logarithmic method. Those parameters were then used in mathematical models of the TGA decomposition curves. They showed good agreement with the experimental results therefore proving the accuracy of the kinetic parameters. Attempts at stabilisation of the polymer using commercially available antioxidants showed that it is possible to enhance polyaniline stability even further. The secondary antioxidants used (trivalent phosphorus and divalent sulphur containing compounds) demonstrated a more positive effect on the stability of the polymers than the primary antioxidants (hindered phenols). However, even in the best conditions only a minor reduction in weight loss of the polymers can be obtained.

Environmental considerations have led to the phase out of chlorofluorocarbon (CFC) refrigerants from the domestic refrigeration industry. One intriguing aspect is that the chlorine in CFCs is a good lubricating agent and any deterioration of system performance may adversely influence other environmental considerations. Based on the above, the aim of this research is to address the sustainable development of domestic refrigeration systems using the replacement refrigerant HFC-134a. The work focuses on the emissions that may arise if the electrical consumption of the product deteriorates or its durability is curtailed. Tribological characteristics on compressor components influence both of these product attributes and therefore a thorough system analysis was carried out. An in-house built experimental test rig, which monitored slight variations in the electrical power drawn by a reciprocating hermetic compressor, was used under different experimental conditions. Furthermore, a detailed life cycle assessment on a domestic refrigerator was performed to help quantify the ensuing environmental burdens. In this way, a relation between tribological characteristics, power consumption and environmental impact was studied. Results have shown that the CFC substitute will increase friction and wear characteristics on the aluminium alloy connecting rod and the steel gudgeon pin. These characteristics led to an increase in the electrical energy consumption of the compressor such that the indirect global warming implications are set to rise with HFC-134a. If the sustainable development of this product is to be ascertained then a change in refrigerants alone will not suffice. New design considerations, primarily aimed at servicing and extending the life of the hermetic compressor itself, are considered. This work helps stimulate new ideas to address environmental issues influenced by traditional engineering disciplines. For this reason additional future research work, which will help determine these implications further, is outlined.

No description available.