Previous studies of high-density polyethylene pipes have been based on the premise that residual stresses have no effects and have almost no role to play in the failure and performance of theses pipes. It is thought that previous studies have underestimated the effects of the residual stresses in pipes at the design stage particularly when assessing pipe-soil interaction and ground loading effects. This project tried to assess the effect of residual stresses in soil-pipe interaction of HDPE (PEIOO) pipes, and opened two main areas of research: (a) to investigate the actual residual stress profile in the pipes as a result of the manufacturing process; and, (b) to take these residual stress profiles, which have been previously ignored, in consideration to assess the performance of the pipe and the surrounding soil. A review of the existing techniques available for the determination of residual stresses was carried out and a literature review was done on how these techniques were used by various authors. On the whole, most of these techniques involved destructive tests that are believed, here, to alter the residual stress profile and magnitude in the pipe wall. The current study has tried to develop an innovative stress-optical technique for the determination of residual stresses with minimal alteration to the residual stress profile and its magnitude. After determining the residual stress profile and magnitudes by the new method, the interaction of the residual stress with internal pressure effects and ground loading effects on pipes is studied. The studies included the numerical modelling of the pipe when the residual stress in the pipe wall incorporated and the pipe subjected to internal pressure loading as well as external loadings from the weight of the surrounding soil. A number of earlier researchers have investigated the soil structure interaction parameters which affect the structural behaviour of buried flexible pipes. However, to date none of the studies have incorporated residual stresses in pipe-soil interaction modelling and the current study has raised awareness of the consequent absence in current design procedure [BS EN 1295-3; 1998].

This thesis focused on comparing various levels of a coagent (bismaleimide, BMI) within an unfilled fluoroelastomer (FKM) in both the cured and uncured states, and determining whether high levels of coagent could still produce an elastomer with acceptable mechanical properties. Further, to determine any links between morphology, cure chemistry/kinetics, and the mechanical properties of the material. Adding BMI as a coagent, even at higher than normal loadings, was shown to produce a material with acceptable mechanical properties (as per ASTM D2000). This conclusion is different to that drawn from literature, where it is suggested that materials with high levels of coagent are brittle and cannot form ‘useful’ products. In the uncured state, the BMI powder acts as a filler of low structure. In the cured state, the BMI coagent also acts as a filler, with SEM and EDX analysis demonstrating that any domains of coagent acting as a filler were below the resolution of the microscope, even though DSC analyses indicated that the two materials were immiscible. The effectiveness of the reinforcement using BMI as a coagent at high loadings has shown to be very high; potentially greater than that of some carbon blacks in other elastomers. With increasing levels of BMI coagent, it was also shown that the molecular weight between cross-links decreased. This occurs even though the elastomer chains can only be cross-linked at the chain ends. Therefore, it is proposed that the BMI is forming filler-like domains. However, these interact with the elastomer molecules, restricting chain mobility. Following progression of the cure process was possible using infrared analyses and by rheometer studies, with infra-red analysis shown not to be as reliable as utilising the rheometer. The cure reactions associated with increasing BMI content were non-linear with regards to Arrhenius plots. This demonstrates different competing reactions when curing the material.

The most common failure mode for polyolefin pipes is slow crack growth. A crack is preceded by a craze, a voided wedge of material bridged by highly deformed fibrils. Upon failure of the fibrils, the crack propagates. Both the tendency of the material to form voids and the strength of the fibril at the craze - crack interface are governed by the effective entanglement network. The effective entanglement network comprises all the intermolecular junctions in the material that can effectively transfer load at the time scale of the experiment. In this work, the effective entanglement network of bimodal polyethylene is probed through tensile and creep measurements. Bimodal polyethylene is the industrial standard material for polyethylene pressure pipes, and consists of a high molecular mass, branched fraction and a low molecular mass, linear fraction. The former is responsible for the resistance to slow crack growth, the latter for enabling processing. In the first part of the work, the influence of molecular mass and branch content of the high molecular mass fraction on the effective molecular network is studied. It is found that only a combination of high molecular mass and high branch content increases the resistance of the network. In the second part of the work, the high molecular mass fraction of the bimodal polyethylenes is isolated. Again, a combination of high molecular mass with high branch content results in a higher effective entanglement network, and overall the resistance to deformation is higher in these materials than in the bimodal materials. It is concluded that the resilience of the network depends on the available network density and the friction caused by side chain branches. Independently of the morphological origin of this friction in the solid material, it can be expected to vary with the monomeric friction in the melt.

The bonding of rigid PVC to a plasticised PVC film using a reactive hot melt polyurethane adhesive has been investigated in order to improve the stability and durability of the bonding between the PVC and the adhesive. (The primers used to modify the surface of rigid PVC are mainly solvent-based products, either methylene chloride based or methyl ethyl ketone based). With Adhesion Promoters, such concerns are environmental (High VOC emissions and clean-up costs), introductions of dirt, high maintenance costs, and safety. Chlorinated solvents, most commonly used in Adhesion Promoters, are highly flammable and toxic which in turn is dangerous to plant and personnel alike. These solvent-based products were band by European Union environment agency in2011. Alternative surface modification technique should replace the solvent prima to modify the surface of the commercial PVC. Consequently the flame treatment technique was employed to modify the surface of the commercial PVC before bonding to a plasticised PVC film by using a reactive hot melt polyurethane adhesive. Before surface modification of the PVCs, the PVC samples were investigated by employing surface analysis’s techniques such as X-ray photoelectron spectroscopy (XPS), contact angle measurements (CAM), atomic force microscopy (AFM) and energy dispersive X-ray (EDX) and DMA. In order to avoid the damage of the PVC samples while they expose to X-ray irradiation. Initially, XPS and EDX were employed in a X-ray degradation study of PVC to determine the maximum time a PVC sample can be exposed to an X-ray source where X-ray has minimum effect on the surface of PVC. The samples used in the degradation study were pure PVC (drop cast in THF on to aluminium foil to produce a PVC film as reference) and three industrial PVC blends. EDX analysis of a pure PVC specimen exposed to an X-ray source showed 5% degradation after ten minutes X-ray exposure. Additionally, a further degradation study was undertaken in which a 1mm diameter gold disc was sputter coated on to PVC sample surfaces. This study revealed that the PVC concentration decreased due to Xray degradation, however, the Au/C ratio remained constant suggesting there was no redisposition of C on to the PVC samples. A liquid propane gas (LPG) based flame treatment was used to modify the surface of rigid PVC (Veka) to improve its wettability and its adhesive properties. The surface properties and chemistry of the modified surface were characterised by CAM, XPS and AFM. Results show that the LPG flame treatment of the PVC (Veka and Rehau) produces both morphological and compositional changes of the surface. LPG flame treatment of the PVC V and R resulted in an increase in the surface free energy of the PVC surface. CAM result for the LPG flame treated PVC showed increased wettability of the PVC sample. The ultra-low-angle microtomy (ULAM) technique was developed to impart a ultra-low –angle taper through polymeric multilayers at ambient temperatures. Here the ULAM technique has been enhanced by in situ cooling of the samples using a cryo-stage (C-ULAM). XPS line scan analysis across a UV primer/PVC interface exposed using C-ULAM indicates penetration of UV primer in to the PVC formulation. XPS line scan analysis of C-ULAM exposed PU/PVC and PVC/PU/PVC interfaces shows penetration of PU in to PVC formulation. The UV primer shows greater penetration in to the PVC (ΔZ = 8nm) than reactive hot melt PU adhesive (ΔZ = 5nm) due to its application in the liquid phase at ambient temperature. The penetration of PU in to the PVC increased after LPG flame treatment of the PVC due to changing surface roughness of PVC by flame treatment. Dynamic Mechanical Analysis (DMA) was employed to investigate effect of LPG flame treatment on the mechanical property of the PVC samples, nineteen months after surface modification of PVCs samples by LPG flame treatment. The DMA results indicate that when the PVC sample treated by flame while the release agent is on the surface of the PVC, the release agent and PVC promote a strong bond and therefore become one solid sample together. The result was indicated that, an increase of 10% in storage modulus, from 8083 MPa for samples without RA to 8822 MPa for samples with RA. These results are in agreement with the results from AFM analysis. By comparing the result of the tan delta of PVC-V with release agent before and after flame treatment, it can be seen that the effect of flame treatment on tan delta profile is not significant. Also the temperature value at tan delta peak indicates the value of glass transition temperature. The fact that this has not significantly changed indicates that the nature of the material has not changed after the flame treatment. In order to study the mechanical property of sandwich layer samples, made of (Rigid PVC/PU adhesive/ Plasticised PVC), with different curing system the Dynamic mechanical analysis (Three point bending/ DMA) of all sandwich layer samples were carried out nineteen months after they have bonded together. The result obtained from DMA results shows 10% increase on loss modules test of sandwich layers, which bonded while prima was applied on the surface of the PVC.

Polyethylene (PE) is the most produced polyolefin worldwide. Since recently discovered long-chain branches (LCB) have been shown to improve the processability, this thesis concentrates on the synthesis of new catalysts capable of producing long-chain branched polyethylene (LCB PE), the investigation of the mechanism which leads to LCB, and the control of the branching degree. The synthesis of new Group IV metal complexes with aromatic carbon-donor ligands which are η1-bound to the metal centre is described. These ligands include biphenyls, diphenylpyridines and terphenyls. Furthermore, an amido complex has been prepared and its synthesis and characterisation is presented herein. All complexes with carbon-based ligands are highly sensitive to air and moisture. Only the use of metal precursors with electron donating ligands enabled the formation of such complexes and it is concluded that electron donating ligands stabilise the electron deficient metal centre and metal-carbon bond. Polymerisation studies showed that the new complexes are active ethylene polymerisation catalysts. Their activity usually increases with temperature. The effect of hydrogen on the polymerisation activity cannot be predicted. Sensitive rheology measurements of the polymer melts revealed the presence of long-chain branches and it has been shown that the Group IV metal complexes with carbon-based ligands described in this thesis are producing LCB PE. Initial experiments towards the investigation of the long-chain branch forming mechanism are described within this thesis. Although not finished, a suitable route to complexes bearing a long alkyl chain has been established, which can be pursued in further studies. A series of tertiary-alkyl amines has been prepared and reacted with a silane to give the targeted aminosilane ligand. The effect of alkyl chain substituents on a cyclopentadienyl ligand in metallocenes has additionally been investigated with respect to the formation of LCB. In order to control the number of LCB in a PE resin, a bicatalytic system involving a bis(imino)pyridineiron catalyst that produces linear PE, an α-diiminenickel catalyst that produces branched PE and a chain transfer agent (CTA) was investigated. The combination of chain shuttling and chain walking as common mechanisms involved in ethylene polymerisation with late transition metal complexes showed to be a promising approach for the control of branching in PE while using ethylene as only monomer feed. Not only can branching be induced by carefully selecting the catalyst ratio and amount of CTA, but it has been shown that chain straightening occurs.

This thesis is concerned with the development of the Ketonex dispersion process in order to reliably and reproducibly produce PEKK dispersions with controlled properties, together with the modification of pre-existing process parameters to achieve a range of particulate PAEK copolymers. Specific emphasis was placed on industrial considerations, pre-commercial scale-up and addressing potential materials applications. Chapter 1 explores well established methods for the production of PAEKs by both nucleophilic and electrophilic routes. General materials properties are described, and structure-property relationships are discussed. Chapter 2 describes in detail the process parameters associated with the Ketonex dispersion process. Parameters are discussed on a laboratory scale and are related to scale-up, industrial and commercial considerations. Chapter 3 evaluates the production of PEKKs with a range of T:I ratios by the dispersion process. The PEKKs are analysed using a range of techniques and are compared to literature data for process evaluation. Chapter 4 discusses the theory behind the action of the benzoic acid dispersant used in the dispersion process, which results in the production of fine particulate PEKK. A hypothesis involving the nucleation of polymerisation by aluminium benzoate is proposed. Chapter 5 demonstrates how the dispersion process can be modified to produce a range of PAEK copolymers. The incorporation of imide and sulfone co-monomers are evaluated in detail, while a selection of alternative monomers undergo preliminary evaluation. Chapter 6 addresses an epoxy toughening application. Amine end-capped PAEKs are produced by the dispersion process by in situ functionalisation. A protected end-capper is devised, its attachment and deprotection confirmed through a model compound approach and is successfully applied to the polymerisation system.

No description available.

Polyvinyl chloride was oriented by hot drawing. The deformation was investigated under uniaxial tension at room temperature and at 50°C. The onset of yield was localised in deformation bands of which two kinds, referred to as type 1 and type 2, were observed. Type 2 bands formed before type 1 bands, but only type 1 bands developed into a running neck. The yield behaviour could be satisfactorily accounted for by a yield criterion based on the von Mises criterion, provided that a term representing an internal compressive stress in the molecular alignment direction was included. The internal stress was found to increase from zero with increasing prior extension ratio and birefringence, and was also equal to the true stress acting on the material during the initial hot drawing. The inclusion of a hydrostatic stress term in the criterion, the application to anisotropic materials of the Coulomb criterion and a critical strain form of the von Mises criterion are considered. Optical anisotropy changes are discussed in terms of an affine deformation model, which was found to apply for deformation at room temperature and 50°C, but not at 71°C and 90°C. The model has also been applied to the deformation, at 50°C, of oriented polyvinyl chloride, the molecular alignment of which was described by three different distribution functions. The agreement between theory and experiment was best for what is referred to as the Kuhn and Grun type 1 distribution. Stress whitening, which developed during hot stretching, is associated with changes in the room temperature deformation behaviour. There was a yield fracture transition at lambda[o] = 0° and a change in ductile fracture behavior at other values of lambda[o]. The ductile fracture direction in stress whitened material has been accounted for by a theory which proposed that the minimum energy was used in propagating the fracture. Two different kinds of type 1 bands were observed in oriented polyethylene. It is suggested that crystallinity may affect the position of the minimum yield stress.

The treatment confines itself to the analysis and design of components compression-moulded in glass-reinforced polyester systems, with particular reference to fan wings and associated mouldings. The first of the three parts develops approximate analysis to express the behaviour of simplified standard fibre arrays. No claim for rigorous accuracy is made, the intention being to demonstrate the mechanics of the composite material rather than to express its performance in precise terms. Expressions are, however, derived for various parameters and carried into the second section for comparison with measured quantities. The second section deals with extensive mechanical tests carried out on standard fibre-matrix systems. The test pieces were compression-moulded under moderate control conditions to simulate commercial practice, so that some estimate of the variation in properties, to be expected in such conditions could be obtained. Under static test conditions this variation is found to depend upon the quantity being tested; tensile test results show, greater scatter in 'weak' than in 'strong' systems, due generally to the greater influence of matrix imperfections in the former categories, while shear results showed, considerable variation in all categories. Some variation, particularly in the latter case, could be accounted for by the simple test methods employed. Further tests included fatigue, creep and thermal expansion, but these were insufficiently exhaustive to show any decisive trends. Agreement with some of the formulae develpped in the first part is found to be good; in other cases an empirical correction offers reasonable correlation, while in some fields -particularly dealing with thermal expansion - no meaningful- basis for comparison can be established. The third section discusses the problems of design in the context of extensive testing of fan wings. Many of the test results unfortunately had to be discarded, either through irrelevance or through lack of information concerning the basic structure, all the test wings, having been moulded, elsewhere. It is also to be regretted- that the test programme was terminated before analysis was complete, so that no further tests could be carried out to resolve ambiguities in the final breakdown. Examination of failure modes, however, indicates clear errors in the design of the existing wings, and suggestions are made for an improved design. Further analysis makes it clear that the range of materials used in current production will not permit compression moulding of wings for fans greater, than 60 in. in diameter for 4-pole 50-c/s operation, or greater, than 48 in for 2-pole speeds, no matter how sophisticated the method of production may become. It is shown that design processes based upon the analysis generated in the first two parts may only be applied with advantage where the moulding charge is of the complex form required for high strength, implying an essentially preformed structure with little flow during moulding. Simpler charges for lower, strength duties may be formulated by simple rules, but can only develop optimum mechanical properties through, trial and error in the moulding sequence. No attempt is made to enter into detailed comparisons with the work of other experimenters. The basic theory in the first part indicates similar trends to those postulated in similar simple theory by Shaffer7, Corten8, Jones9 and Krenchel10, but the compression moulding practice using glass reinforced material in the second and third parts does not appear to have been covered elsewhere.

No description available.