The frictional behaviour of rubber is a topic of great interest and importance due to the invaluable uses of rubber in industry. The very particular behaviour of rubber also makes rubber friction a fascinating subject matter. Despite this it is still a topic not well understood. Previous studies have attempted to link the fracture mechanics of rubber crack propagation to the adhesive friction of rubber. The feasibility of such an approach to the adhesive friction of a rough rubber against a smooth surface, a configuration which can occur in various situations such as rubber seals or windscreen wipers, has been investigated. Rolling friction, described well by a fracture-like peeling process, is used to evaluate the viscoelastic dependence of sliding friction for various combinations of surfaces. A novel use of rubber is proposed as a material for particles to be used for jamming based soft robotics applications. This area of soft robotics is comparatively new and the materials that are being used at present are neither well established nor have been examined in great detail. Rubber would offer a material easily manufactured to desired shapes and dimensions with a wide range of moduli allowing modification to suit specific applications. The effect of jammed rubber particles on the response of a jammed packing to an externally applied load is examined. The evolution of inter-particle forces is studied using a rheometer configuration. Finite element techniques and modelling are employed to study the rubber in more detail.

This work reports the investigation of Cu-mediated polymerization systems and its limits, in order to obtain functional branched polymers, in particular star-shaped and graft-shaped polymers. A novel initiator structure has allowed developing a new approach to synthesise sequence controlled multiblock star polymers via Cu-mediated reversible deactivation radical polymerization (RDRP) in water. This technique allows the preparation of pentablock star shaped polymers in just under 90 minutes of reaction time. The obtained polymers had a good agreement between theoretical and experimental molecular weights and excellent control over molecular weight distribution. Alternatively, the Cu-mediated RDRP of star polymers using a British 1 penny coin was described, displaying similar results as in the literature, providing better experimental conditions. As the copper coin was recovered unharmed, the catalyst was found to be economically very effective. Furthermore, poly(2-ethyl oxazoline) (PEtOx) was polymerized with good control and partially hydrolysed to poly(ethylene imine) (PEI) to yield PEtOx-r-PEI using a microwave reactor. The secondary amines of PEI was converted to macroinitiators, to allow the polymerization of acrylamides in aqueous medium, resulting in graft type polymers based on a poly(oxazoline) backbone with acrylamide side chains. Finally, the synthesis of carbohydrate-monomers was described, which allows to obtain monomers with a different number of carbohydrates (one, two or three). These monomers were polymerised via aqueous SET-LRP, to explore their interaction with carbohydrate binding lectins and to understand the impact on binding of carbohydrate density on polymers and polymer chain length.

Hybrid energy harvesters (HEHs) targeting multiple energy forms have been drawing increasing interest in recent years. While large scale photovoltaic power plants are capable of providing energy for domestic usage, research has also been focused on kinetic energy harvester with less power output which can be integrated into self-powered electronics such as implantable device, remote wireless sensor, wearables, etc. A number of successful designs of hybrid energy harvesters have been demonstrated which could scavenge solar and kinetic energy simultaneously. However the structures remain complicated; the majority of the designs involve different types of energy harvesters connected in series, which involves complex fabrication processes. Here, a simple structure based on a p-n junction piezoelectric nanogenerator (NG) was designed. The utilization of columnar piezoelectric n-type ZnO nanorods coated with light absorber layer enabled the device to harvest both kinetic and solar energy. This was adapted to either form a N719-based dye-sensitized solar cell (N719-HEH), or a perovskite solar cell (PSC-HEH). To allow high processing temperatures while maintaining mechanical flexibility, Corning© Willow™ (CW) glass substrate was used and compared to the more common ITO/PET. CW showed 56% lower charge transfer resistance and a related 4 times fold increase in power conversion efficiency for N719-HEHs. Oscillation (NG effect) and illumination (PV effect) testing indicated that both N719-HEHS and PSC-HEHs operated as kinetic and solar energy harvesters separately, with the current generated by the photovoltaic orders of magnitude greater than it from mechanical excitation. In addition, under illumination, both N719-HEHs and PSC-HEHs demonstrated further current output enhancement when oscillation was applied. The fact that the current output under NG+PV condition was higher than the summation of current output achieved under NG and PV conditions individually, suggests the piezoelectric potential originated from ZnO affected the charge dynamics within the devices. Thus, HEHs with enhanced output were successfully designed and developed.

Echinoderms, for example sea cucumber, contain a unique collagenous tissue, with special biomechanical properties, which could near-instantly change their mechanical state (going from stiff to soft, and vice versa, in less than a second). However, the structure-function relation has so far not been exploited. Understanding how the material design of mutable collagenous tissue (MCT) enables this remarkable dynamical mechanical behaviour will help enable development of new biomaterials with adaptable mechanical properties. Currently, it is hypothesised that MCT can rapidly form crosslinks between the collagen fibrils and stiffen the interfibrillar matrix under neural control, but this had never been shown directly. In this thesis, we carried out an experimental study of quantifying how the interfibrillar matrix response to stimuli agents, to generate active forces and change conformation using a synchrotron in situ X-ray nanomechanical imaging method. By the uncovering of the mechanisms of active force generation, a valuable guideline, which could be applied in bioinspired constructs that response to external stimuli, can be obtained.

It is a well-known phenomenon that during Marangoni condensation of binary mixtures, a small concentration of more volatile constituent with smaller surface tension gives significant heat transfer enhancements. This is due to surface tension gradients causing instability in condensate film, resulting in a pseudo-dropwise mode of condensation which resembles closely to dropwise condensation of pure fluid on the hydrophobic surface, consequently, the film gets thinner with lower thermal resistance across the condensate film and thus higher heat transfer coefficient is achieved. Marangoni condensation of steam-ethanol mixtures has been widely investigated in the past. However, Marangoni condensation of self-rewetting fluids e.g. steam-butanol is yet to be investigated where the constituent in a small concentration is a less volatile component. Marangoni condensation of steam-ethanol, steam-butanol and steam-propanol mixtures has been investigated on a horizontal smooth tube at an atmospheric pressure. For all experiments, concentrations by mass in the boiler feed when cold prior to start of the experiment were 0.001%, 0.005%, 0.01%, 0.025%, 0.05%, 0.1%, 0.5% and 1.0%. The coolant temperature rise was measured accurately with a ten-junction thermopile. Tube wall temperature was measured using four thermocouples embedded in the test tube wall. Effects of pressure and vapour velocity over a wide range of vapour-to-surface temperature difference have been investigated. Care was taken to avoid error due to the presence of air in the vapour. Marangoni condensation of steam-butanol and steam propanol mixtures show significant heat transfer enhancements compared with that of steam-ethanol mixtures. Higher Heat flux and heat-transfer coefficients were observed. For the steam-ethanol mixtures, enhancement ratio (heat flux or heat-transfer coefficient divided by the corresponding value for pure steam condensation on a horizontal smooth tube for the same vapour-to-surface temperature difference and vapour velocity) of 5.5 was found at an ethanol concentration of 0.01%. For steam-butanol mixtures, the maximum enhancement ratio was found to be 11 at a concentration of 0.005% and 0.01%. For steam-propanol mixtures, the maximum enhancement ratio of 8.5 was found at the same mass concentrations as steam-butanol mixtures. Enhancement ratio was generally higher at lower ethanol concentrations, increases at first with increasing vapour-to-surface temperature difference and subsequently decreases at high vapour-to-surface temperature difference. Finally, a semi-empirical model was proposed to predict the Marangoni condensation of steam-ethanol mixtures based on the vapour phase diffusion theory of Sparrow and Marchall (1969) and pure steam dropwise theory of Rose (2002).

This thesis concerns crack growth phenomena in rubber. It is widely known that a relationship exists between the magnitude of the stored energy release rate available to drive a crack, called the tearing energy (7'), and the resultant crack growth rate. For rubbers this basic relationship is said to be a characteristic of the material. The magnitude of T is related to both the visco-elastic losses and the crack tip diameter (d) However the actual size of d and its relationship with the viscoelastic losses is not clear. This thesis examines the crack growth behaviour in relation to d and the visco-elastic losses for a wide range of rubbers, whose visco-elastic properties are altered either by swelling in a liquid, altering the test temperature or the cross-link density and by the incorporation of fillers. Static, constant T, crack growth tests were carried out. These revealed that two different crack growth processes exist. For the fast crack growth process, T is determined by variations in the visco-elastic losses alone. For the slow crack growth process, T is determined by variations in both the visco-elastic losses and d. It is proposed here that the factors, which alter d, are associated with cavitation ahead of the crack tip for unfilled materials and with strength anisotropy for carbon black filled materials. In cyclic crack growth tests, the crack growth per cycle, dc/dn, can be considered to result from the sum of time and cyclic dependent crack growth components. For the first time, the detailed magnitudes of the contribution of each of these components to dc/dn have been determined, for a wide range of materials and mechanisms responsible for this behaviour are postulated. Also crack growth tests, both static and cyclic, were extended to very large extensions. Lastly this investigation revealed that the tensile strength for both ciystallising and noncrystallising rubber can be predicted using the tearing energy concept for a variety of loading regimes.

The research carried out in this thesis describes the processing of liquids and ceramic suspensions, having a viscosity >100mPa s, using electrostatic atomization, mainly in the stable cone-jet mode. Electrostatic atomization, also called electrospraying, refers to a process where a liquid or a suspension is made to flow through a needle. The liquid or suspension is subjected to a high voltage maintained between the needle and a ground electrode. Two major physical properties, namely electrical conductivity and viscosity, affect electrostatic atornization in the stable cone-jet mode and the investigations described in this thesis focussed on the latter. Firstly, a set of liquid mixtures were prepared using distilled water and glycerol. The dc electrical conductivity of these mixtures were kept constant and the viscosity was varied. The mixtures were subjected to electrostatic atornization and in each case the mode of atornization, the cone/jet characteristics and relic sizes were studied as a function of viscosity. The effect of applied voltage on the conejet mode electrostatic atornization of glycerol having a viscosity of 1338mPa s was also investigated. Secondly, the possibilities of electrostatically atomizing ceramic suspensions were studied in detail. Several alumina suspensions were used including one containing a high volume fraction of solids (20 vol. % - the highest filler loading attempted to date using any jet-based processing route). Applied voltage - flow rate - atornization mode maps were constructed for this suspension incorporating even pico-flow rate regimes. This is a new input into the aerosol science and engineering literature. This section also highlights the importance of controlling the applied voltage and flow rate as these parameters affect the jet diameter and relic/droplet size generated. The effect of the geometry of the ground electrode used for electrostatic atornization was also investigated. In particular, the use of a point-like ground electrode was studied for the very first time. The third and most innovative facet of this research was the discovery of ceramic electrostatic atornization printing (CEAP) and the use of electrostatic atornization to produce ceramic foams. In CEAP a point-like ground electrode is used to focus the spray which was printed as characters, collection of characters and single tracks. This investigation was extended to explore the printing of multiple tracks produced with the aid of several needles and ground electrodes which worked simultaneously. A ring shaped ground electrode was used to electrospray ceramic droplets onto a polyurethane template and this paved the way for the development of a new method to prepare open-cell ceramic foams with a very high porosity. This method was extended to prepare ceramic structures and complex components.

The positive temperature coefficient (PTC) effect in conductive polymer composites (CPC) are still poorly understood with the thermal expansion of the polymer matrix accepted as the main cause. This thesis aims to study a model system able to explain the effect of the filler size and shape on the PTC behaviour of CPCs. Silver coated glass spheres and flakes are used as conductive fillers due to the ease in controlling uniform size and shape. In a controlled system it was demonstrated that the PTC intensity increases with increasing filler size and with decreasing filler content, both for conductive fillers. Combinations of different conductive fillers were investigated to explore the possibility to obtain both low percolation thresholds and high PTC intensities. Model systems in which at least one of the two conductive fillers is of relatively homogenous size and shape were used to facilitate unravelling some of the complicated relationships between (mixed) conductive fillers and the PTC effect. The PTC intensity of mixed fillers composites were dominated by the filler with the lowest PTC intensity, even at very low volume fractions. The PTC intensity was not only influenced by the conductive particle size but also by its size distribution. The effect of difference in linear coefficient of thermal expansion (CTE) of conductive fillers and polymer matrix based on a change in filler core on PTC behaviour was investigated. Damage to the particles due to the poor adhesion between the silver coating and the PMMA bead lead to the composite behaving like mixed filler composite. Hybrid polymers filled with silver coated glass flakes was also examined in order to enhance the PTC intensity. The PTC intensity of the composite increased with increasing PPE content but the negative temperature coefficient (NTC) effect was observed in all the composites.

This work was on the effect of electric current on the processing of ceramics. The focus was on electromigration/electrochemistry and plasma effects. While there is no solid evidence that there is plasma in Spark Plasma Sintering, (SPS), newer techniques e.g. flash, use different conditions so there is an interest in understanding the conditions under which a plasma forms. The minimum arcing voltage was found from literature to be from 10-15V for materials of interest. This is above that found in SPS (10V). However, due to the many contact points in a powder compact much higher voltages (50V) were required in practical experiments. Optical spectroscopy was used to verify the formation of a plasma, and emission peaks from the powder compact material were visible implying they were vaporised and formed the plasma. Electromigration was exploited to alter the oxidation of zirconium diboride, by passing current through the oxide layer (120μm zirconia base grown at 1200°C) oxygen could be pumped either away or toward the diboride bulk. Small cubes (3mm) of diboride had platinum foil electrodes applied on both sides and oxidation was performed at 1400°C for 5hr. Without a field the oxide grew to 360μm, by applying 10V and 100mA the oxide grew to 150μm under the +ve electrode but 1400μm under the -ve electrode. Electrochemical reduction was believed to have occurred due to the electrical properties of the material changing during oxidation and visible blackening of the oxide. Combining the techniques from both earlier works, a contactless flash sintering setup was developed. This used two plasma arcs as electrodes to heat and pass current through the sample. Various materials, currents and times were used, but the best result was with SiC:B4C which was sintered in 3s with 6A, the microstructure showed sharp grains, no segregation and limited grain growth ( initially 0.7μm SiC and 0.5μm B4C, this grew to 1.1μm and 1.4μm). This was the first recorded case of contactless flash sintering and the technique has the potential to sinter ceramics in a continuous manner.

Rubber abrasion is one of the most important properties for rubber products, such as tyres. However, due to its complexity rubber abrasion is still a very challenging topic in rubber research. Rubber abrasion is not governed by a single mechanism. Different mechanisms can dominate the abrasion behaviour depending on the rubber compound, base polymer type, loading severity, contact conditions, testing temperature and chemical environment. This study investigates the different mechanisms for rubber abrasion and the transition between these mechanisms using two types of abrasion apparatus, a blade abrader and a surface abrader, respectively. Blade abrasion was used to generate the abrasion pattern. Once the abrasion pattern was formed on the rubber surface under unidirectional sliding, the underlying mechanism was primarily one of fatigue crack growth, which is referred as "fatigue wear" in the literature. An independent pure shear fatigue test with various loading profiles was conducted to predict the crack growth rate using a fracture mechanics approach during these abrasion tests. The tearing energy during blade abrasion was calculated using a fracture mechanics approach. A Finite Element Analysis (FEA) technique using the Virtual Crack Closure Technique (VCCT) was adopted. The VCCT approach was a simpler, faster and more reliable approach to derive the tearing energy under these complicated large strain contact conditions. The prediction of the abrasion rate using this independent measurement of the crack growth resistance of materials worked best for unfilled SBR material. A bespoke surface contact abrasion machine was used to investigate rubber abrasion on silicon carbide sandpaper under both dry and wet conditions. Depending on the materials, contact conditions and sliding velocity, two different mechanisms were observed. The first being a mechanochemical degradation, during which a sticky layer was generated on the rubber surface. This behaviour is also called "smearing wear". The second failure mode resulted from a purely mechanical fracture named "abrasive wear". It seemed that the carbon black filled rubber was more susceptible to smearing wear than the silica filled one. Higher sliding velocities promoted smearing wear, possibly due to higher temperatures being generated at the interface. Alternatively, water lubrication was seen to promote abrasive wear. Therefore, the abrasion mechanism changed to more rapid abrasive wear under wet conditions, which resulted in a significant increase in the rate of weight loss. Finally, the sticky debris generated during the smearing wear was characterised using various different techniques. This revealed that the sticky debris had more oxygen and lower carbon and sulphur content. It contained a greater amount volatiles and generated more char formation during its degradation in the air. The molecular weight of the sticky debris was much lower when compared to the original uncured rubber. It seemed that in the sticky debris the filler network can slowly recover and the degraded polymer chains can re-absorb back onto filler surface forming "bound rubber", which leads to faster rates of weight loss.