Thesis (Ph. D.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 487-524).

Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 174-176).

Thesis (M.S.)--Ohio State University, 2006. / Includes bibliographical references (leaf 111). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 101-107).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (p. 89-102).

This is the thesis which explains the progress made in the analysis, simulation and testing of plastics forming. This progress can be applied to injection and compression mould design. Three activities of plastics forming have been investigated, namely filling analysis, cooling analysis and ejecting analysis. The filling section of plastics forming has been analysed and calculated by using MOLDFLOW and FILLCALC V. software. A comparing of high speed compression moulding and injection moulding has been made. The cooling section of plastics forming has been analysed by using MOLDFLOW software and a finite difference computer program. The latter program can be used as a sample program to calculate the feasibility of cooling different materials to required target temperatures under controlled cooling conditions. The application of thermal imaging has been also introduced to determine the actual process temperatures. Thermal imaging can be used as a powerful tool to analyse mould surface temperatures and to verify the mathematical model. A buckling problem for ejecting section has been modelled and calculated by PATRAN/ABAQUS finite element analysis software and tested. These calculations and analysis are applied to the special case but can be use as an example for general analysis and calculation in the ejection section of plastics forming.

The application of flow injection analysis into the simultaneous determination of two or more components has been challenging for many years. Various detectors such as ultraviolet/visible absorption, fluorescence, and electrochemical detectors, have been used individually or in combination with each other. Combining two optical detectors such as fluorescence and ultraviolet/visible absorbance, however, has always been challenging due to their incompatibilities. However, the recent developments in fibre optics, solid-state light sources and miniaturised charged coupled devices (CCD), allow novel designs and most of the incompatibilities be circumvented. A flow injection manifold can now be adapted so that only one flow cell is used along with a diode array CCD detector that can detect both fluorescence and absorbance simultaneously. The initial development and testing of such dual detection system is described in this thesis.

La maîtrise des cycles thermiques lors des opérations de moulage des élastomères est un enjeu important pour les industriels de la mise en oeuvre du caoutchouc. L’objectif scientifique de ce travail de thèse est d’atteindre une maîtrise précise des températures dans les moules lors des opérations de moulage et d’optimiser les conditions de régulation thermique de ceux-ci dès la conception. Dans ce travail, nous proposons une nouvelle conception des moules, de son système de chauffage et de régulation permettant la maîtrise des températures au plus près de la matière injectée. L’originalité de ce moule réside dans la réduction de la masse d’acier chauffée et la mise en place de zones de chauffe isolées thermiquement entre elles, indépendamment régulées. Cette démarche a été validée par la mise en place d’un montage expérimental original afin d’étudier les transferts thermiques dans l’outillage lors de l’injection de l’élastomère. Une instrumentation fine et complexe du moule dans les cavités moulantes et les canaux d’injection matière, permet le suivi de l’évolution du champ thermique. Les mesures expérimentales permettent d’étudier les phénomènes thermiques intervenant dans l’outillage pendant les cycles de moulage et vérifier l’homogénéité des champs de températures dans le moule. Il permet de valider la stabilité thermique de l’outillage en cours de production. Ces mesures permettent de construire une base de données expérimentale pour alimenter les outils numériques d’aide à la conception des outillages. Les analyses thermique et énergétique des cycles de moulage ont permis une optimisation des paramètres de process afin de mieux maitriser la consommation énergétique lors de la production pour une qualité de pièce équivalente voir meilleure. / The control of the thermal cycles during the operations of moulding of elastomers is an important issue for the rubber industry. The scientific objective of this work is to reach a precise control of the temperature in the moulds during the molding operations in order to optimize the conditions of thermal regulation of those as of the design. In this work, we propose a new design of the moulds, its heating system and regulation allowing us to control the temperatures closest to the part material. The originality of this mould lies in the reduction of the heated mass of the steel and the installation of heating zones thermally isolating between them and independently controlled. This approach was validated by the installation of an original experimental setup in order to study the heat transfers in the tools during the injection of elastomer. A fine and complex instrumentation of the mould in the moulding cavities and the channels of injection matter, allows the follow-up of the evolution of the thermal field. An experimental measurement makes it possible to study the thermal phenomena intervening in the tools during the moulding cycles and to check the homogeneity of the temperatures fields in the mould. It makes it possible to validate the thermal stability of the tools in the course of production. These measurements make it possible to build an experimental database to supply the digital tools of assistance to the design of the tools. The thermic analyses and energetics of the mouldings cycles allowed an optimization of the process parameters in order to better control energy consumption during the production for an equivalent part quality see better.

The objective of this research project was to carry out the investigation of the relationship between processing conditions, micromorphology and mechanical properties of isotactic polypropylene homopolymer using conventional and shear controlled orientation injection moulding (SCORIM) techniques by systematically changing carefully controlled processing conditions, mould geometry and compound additives. Both SCORIM and conventional techniques were employed for iPP injection moulding using three moulds of different shapes by varying the processing conditions, including nozzle temperature, mould temperature, injection speed, hold pressure and oscillating patterns of pistons. The results obtained were compared so as to indicate the differences in microstructure and physical properties resulting from the two moulding techniques. A range of analytical methods were employed. Optical transmitted light microscopy was used to reveal the skin-core morphology and preferentially oriented fibrous textures. Transmitted Electron Microscopy represented the enlargement of the fibrous alignment. Micro hardness analysed the hardness and isotropy characteristics by measuring the diagonal lengths of the indentations. Mechanical testing determined Young's modulus, the strength and toughness of the mouldings. X-ray diffraction exhibited the distribution of the cc, 6 and 7 crystalline phases of the iPP mouldings. The WAXS Debye patterns confirmed the existence of the preferred orientation through the thickness of the moulding. Differential Scanning Calorimetry analysed the thermal behaviour from the endothermal and exothermal curves. In the initial stage of the study, the polypropylene was moulded in the form of a standard tensile bar on a conventional Sandretto injection machine in order to obtain the basic characteristics of the polypropylene study material, which could then be used to compare with those properties to be gained using the SCORIM technique. A ring mould was then used in a Negri Bossi twin injection machine to investigate improvements in uniformity of micromorphology and dimensional reproducibility of mouldings made possible by four live-feed injection moulding. Later, a study was carried out on injection moulding of polypropylene by varying processing conditions, including three hold pressures, two mould temperatures and two nozzle temperatures for both conventional and SCORIM injection processes by using a rectangular bar mould in a Demag injection moulding machine. In the finial stage, the study explores the influences of composition, in essence a limited range of nucleating agents, and processing methods, and aspects of the micromorphology, dimensional control and the mechanical properties of polypropylene. Polypropylene, as a sernicrystalline polymer, represents a class of materials in which mechanical properties are strongly influenced by processing conditions and micromorphology.

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