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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

The formation and properties of polyamides containing Anthraquinone residues

Crangle, Andrew Alexander January 1974 (has links)
No description available.

Investigation of the thermoforming of polypropylene packaging

McConville, Eileen January 2014 (has links)
Packaging is one of the major fields for plastic materials, with extruded polypropylene (PP) sheet widely used in the production of thin gauge tubs and containers for the food and beverage industry using the thermoforming process. In an increasingly competitive market understanding the fundamental material properties and the effect of thermoforming process settings can help a company deliver material and efficiency savings allowing them to reduce production, manufacturing and development costs. The main aim of this work was to advance the practical understanding of the processing of PP for packaging applications, by linking the fundamental material behaviour to the industrial thin gauge thermoforming process. During this work investigations were carried out into the basic properties of commercial grades of PP and the affect of blending on material and end container properties. The effect of extrusion and thermoforming process conditions on end container properties were also investigated along with large strain mechanical stretching using lab equipment capable of replicating the industrial process settings. Investigations into both the affect of extrusion settings and thermoforming settings have shown that the PP material grade selected can have a greater effect than changes in process settings; with changes in settings having a different degree of effect on the different PP material grades. Therefore it is important for a thermoformer not just to consider the material type but the material grade or percentage blend during product development. This work has also highlighted the fact that complex blends can be created everyday in the industrial thin gauge thermoforming process and these blends will greatly affect t,he behaviour of the material during processing, and the end container properties. Overall the work demonstrates how susceptible PP is to changes in blends and processing conditions and will be particularly relevant to the developing recycled materials area.

Analysis of the stretch blow moulding process and subsequent simulation development

Nixon, James January 2015 (has links)
Injection stretch blow moulding (ISBM) is the most common processing method of producing thin-walled poly (ethylene) terephthalate (PET) containers. With numerous processing parameters and complex deformation, there is still a certain amount of expert knowledge required to successfully convert a PET preform into a useable bottle, capable of passing rigorous post-process testing. The purpose of this work is to develop an accurate simulation of the bottle forming procedure through extensive examination of the input parameters and how they affect the preform deformation and bottle characteristics. By removing the bottle mould, a free-stretch-blow analysis was performed over a large process window. This procedure utilised the digital image correlation (DIC) method with a patterned preform heated using an oil bath. A corresponding simulation was constructed using ABAQUS/Explicit FE solver and a constitutive viscoelastic user material subroutine. A comparison between the experimental and predicted values of internal cavity pressure, stretch-rod force and surface strain was performed resulting in reduced accuracy at low flow rate, sequential-type deformations. Free-stretch-blow trials also highlighted the need for adequate preform storage as increased moisture content affects the deformation behaviour. Reapplying the bottle mould and using the same process parameters revealed that the simulation had difficulties in predicted accurate bottle thickness, particularly at higher flow rate. An insufficient contact friction model was concluded and more insight into the heat transfer and back pressure between the polymer and mould was required. Results from the simulation also demonstrated that the previously assumed incompressible behaviour of PET during bottle formation is incorrect. A novel method of measuring strain levels in all three directions was devised to reveal that deformation mode greatly affects the value of Poisson's ratio. Insight into the ISBM process and development of the simulation has been advanced through this work and key areas of further improvement have been revealed.

Modelling the constitutive behaviour of poly(ethylene terephthalate) for the stretch blow moulding process

Yan, Shiyong January 2014 (has links)
The stretch blow moulding (SBM) process is the main method for the mass production of PET containers. Understanding and modelling the behaviour of PET is critical for design the optimum product and process. However due to its nonlinear viscoelastic behaviour, the behaviour of PET is highly sensitive to its thermomechanical history making the task of modelling its constitutive behaviour very complex. This means that the constitutive model will be useful only if it is known to be valid under the actual conditions of the SBM process of interest. The aim of this work was to develop a material model capable of capturing the deformation behaviour of PET subject to an arbitrary strain history, and to develop a new material characterization method providing new data for the deformation behaviour of PET relevant to the SBM process. In or~er to achieve this goal, a reliable, robust and non-touch characterization method was developed based on the data acquisition system and digital image correlation system to determine the stress-strain relationship of material in deforming preforms during free stretch-blow tests. Considerable experimental work, including conventional biaxial stretching tests and free stretch-blow tests, was carried out to characterize the mechanical properties of the material. These tests revealed the properties of PET under displacement-controlled deformation and load-controlled deformation. The material model was developed based on the original Buckley model in two aspects. One was the development of the 'lock-up' process in the network system, representing the onset of strain-induced crystallization (SIC). Another was the consideration of self-heating effect of PET during the deformation.

Investigation into the colouration of polypropylene

Zeng, Fuquan January 2002 (has links)
Polypropylene (PP) offers many advantages to the textile processor in terms of its durability and end use properties. However, a major technical flaw of PP is its inability to be dyed due to its relative lack of dye adsorption sites and high crystallinity. Therefore it is primarily mass pigmented, with pigment incorporated into the polymer melt prior to extrusion. While this approach offers a successful commercial route it does lack process flexibility. Some research has focused on modifying the polymer structure by incorporating dyeable copolymers or chemically degrading the base polymer by aqueous treatments to create polar groups for dye adsorption. However, both of these approaches have had little success due to processing difficulties, excessive deterioration of polymer properties and cost. In this study the primary thrust of the research has been to evaluate the use of dry gaseous fluorine treatments to modify the PP fibre and create dyeability and better colour fastness. XPS and FTIR indicate reaction between fluorine and the polypropylene fibre and the introduction of carboxyl groups and fluorine into the polymer. The introduction of these carboxyl groups and strongly electronegative negative fluorine leads to the fibre's enhanced basic dyeability. SEM analysis showed the impact of fluorine exposure on fibre surface morphology is relatively small. The effectiveness of pre-treatments on pigment dyeing and printing has also been evaluated. Colour fastness was significantly improved by a gaseous fluorine pretreatment of the textile substrate. The Helizarin Binder UDR pigment dyed system showed better performance in terms of colour fastness than other commercial binder systems evaluated. Optimisation of the binder to pigment ratio has been achieved in order to obtain good colour fastness. The dycability of moulded polyacetal zips was also examined in order to potentially replace the current mass pigmentation process. Fluorine pre-treatments showed no benefits in the overall colouration. properties in terms of long liquor dyeability or pigment dyeing. Of the disperse dyes evaluated the "high performance" SF and XF classes had the best colour fastness, in particular Dispersol Red CBN-SF, Dispersol Blue XF and Dispersol Flavine XF. A range of after-treatments were evaluated and a "reduction cleae, significantly improved the colour fastness. The polyacetal/polyester zip construction offered significant colouration difficulties due to the inherent problem of achieving a uniform, compatible, "soliX' dye shade. Although some success was achieved, commercial utilisation is less likely due to increasing process complexity.

Encapsulation of biocides in poly (vinyl chloride) and their ability to inhibit biofilm formation and biodegradation

Bayley, Kate January 2006 (has links)
No description available.

Synthesis and screening of biocompatible polymers using a multiparallel approach

Jose, Ann Jasmine January 2005 (has links)
No description available.

The synthesis and screening of polymer libraries using a high throughput approach

Mizomoto, Hitoshi January 2004 (has links)
No description available.

Surface etching studies of highly drawn polyethylenes

Tissington, Bryan January 1990 (has links)
No description available.

Morphology and properties of nylon 66 : effects of injection moulding on structure and performance

Jackson, Victor S. January 1973 (has links)
Nylon 66 injection-moulded insulators are used by British Rail outdoors for track insulation. It has been suspected that the conditions of initial moulding and treatment before use represent a significant factor affecting properties over a period of time in this application. A laboratory study has already been reported on the influence of spherulite size on mechanical properties, using a nucleated grade of Nylon 66 to compare with typical unnucleated polymer, but this work throws little light on the problem of unnucleated polymer as such or on the influence of injection conditions and the effects of moisture present after moulding. It was therefore decided to investigate these aspects using a standard unnucleated grade of Nylon 66.

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