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Aqueous polyuethane (PU) colloids, like many other water-borne polymer colloids, have become an increasingly important class of materials in the surface coating industry. Three processing stages, the pre-dispersion, dispersion and postdispersion stages, are generally involved in the production of aqueous PU colloids. However, existing researches have neglected the importance of the dispersion stage. The present study aims to develop better understanding of the dispersion stage during the production of aqueous PU colloids. Non chain-extendable PU pre-polymer (PUp) is used to enable independent study of the dispersion stage and the phase inversion process is chosen due to its widespread industrial usage. Valid drop size characterisation techniques and phase inversion detection methods have been developed in this project. Three different dispersion regions have also been identified by changing the ionic group content of PUp. Each dispersion region is associated with a particular dispersion type. Those are (I) Stable aqueous emulsions that contain small PUp-in-water drops. They were produced using PUp with more than 0.2 mmole/g of ionic groups. (2) Aqueous PUp colloids with 0.05 ~ 0.2 mmole/g of ionic groups. These emulsions contain a mixture of drop structures, including simple drops and different multiple drops. (3) Aqueous PUp dispersions containing less than 0.05 mmole/g of ionic groups. These dispersions are not stable and the resultant dispersions separated when agitation was stopped. Modified phase inversion maps are introduced to represent the occurrence of all three dispersion regions. The modified phase inversion maps are partly analogous to those of conventional non-ionic-surfactant-water (nSOW) systems. The three dispersion regions have also been "reproduced" successfully using external surfactants as substitutes for the internal stabilising groups. A new catastrophic phase inversion mechanism is proposed to explain the existence of all three dispersion regions. Other variables studied during this project include different neutralising agents. different amount of carboxylic acid groups, operating temperatures and material addition rates. In conclusion, this project shows that the phase inversion process is a feasible route for producing aqueous polymer dispersions with little or no added external surfactants. Stable PUp-W dispersions can also be produced below the minimum ionic group content reported in existing literatures.

The degree of carbon black dispersion is a very important consideration in the manufacture of rubber both in quality control and basic research. A study has been made of various aspects of assessing dispersion and the dispersion process of carbon black in rubber. The main objectives of this work were: (1) To investigate the relationship between the light scattered at a fixed angle from the rubber surface and carbon black dispersion and hence develop and evaluate a new dispersion assessment system. (2) To determine the normal variations of industrial rubber mixing installations, and (3) To study the effect of internal mixing variables on black dispersion and other properties of rubber. To achieve these goals a carbon black dispersion assessment system based on an inverted Dark Field Reflected Light (D.F.R.L.) microscope was developed in three versions and successfully tested. The three versions differed in their degree of sophistication and automation and would be expected to find application ranging from routine quality control to research. The basic principle was that a rubber sample (cured or uncured) was cut with a new razor blade and the surface observed in a D.F.R.L. microscope. The light beam from the sample surface is sensed by a photometer and its intensity was shown to be related to black dispersion. In version III an automatic stage driven by two stepper motors was designed and fitted to the microscope to perform object plane scanning. The photometer and the stage were interfaced with an Apple II microcomputer providing the following functions; stage control, photometer control, data acquisition, statistical analysis, data storage and results output. The system was evaluated by taking measurements on several identically formulated compounds differing only in black dispersion. A general rubber goods and a tyre manufacturing installation were studied. Several production batches were sampled at various mixing stages and subjected to black dispersion assessment, cure and vulcanisate properties measurement. Analysis of variance of the results was accomplished with a statistical computer package designated GENSTAT Version 4.03. Factorial experimental designs and multivariate regression analysis techniques were used in studying the effect of mixing variables on black dispersion and other properties. The results are presented in the form of response equations and contour graphs are used to enable second order interactions to be readily identified.

Increasing wind penetration adds to the importance of enhancing the reliability of wind, to mitigate the magnitude and frequency of changes in electricity generation. This work addresses how improvements can be made to reliability through the geographic dispersal of wind farms in Ontario, Canada, using modeled North American Regional Reanalysis data. Optimal configurations of wind farm locations are determined according to two criteria. The first selects combinations of wind farms that follow temporal demand patterns, by maximizing the difference between the energy price and the cost of electricity. The second attempts to select combinations of wind farms that minimize the coefficient of variation in the aggregate output. It is found that there are no wind regimes in Ontario that match demand sufficiently for a viable development strategy, but that combinations of as few as three locations can reduce the coefficient of variation by over 30%, compared to a single region.

Increasing wind penetration adds to the importance of enhancing the reliability of wind, to mitigate the magnitude and frequency of changes in electricity generation. This work addresses how improvements can be made to reliability through the geographic dispersal of wind farms in Ontario, Canada, using modeled North American Regional Reanalysis data. Optimal configurations of wind farm locations are determined according to two criteria. The first selects combinations of wind farms that follow temporal demand patterns, by maximizing the difference between the energy price and the cost of electricity. The second attempts to select combinations of wind farms that minimize the coefficient of variation in the aggregate output. It is found that there are no wind regimes in Ontario that match demand sufficiently for a viable development strategy, but that combinations of as few as three locations can reduce the coefficient of variation by over 30%, compared to a single region.

The primary objective of this thesis was to develop a nucleation regime map to determine the controlling nucleation mechanism as a function of material properties and operating parameters. Two distinct regimes of nucleation were identified. The drop controlled nucleation regime occurs when nucleation conditions are ideal and one drop produces one nucleus granule and the controlling property is the droplet size. The nuclei formation kinetics are fast and the binder droplets penetrate into the powder bed pores almost immediately. In this region, the nuclei distribution reflects the drop size distribution as one drop tends to form one granule provided that (a) drops hitting the powder surface do not overlap - low spray flux Ya and (b) the drop must wet into the bed completely before bed mixing brings it into contact with another partially absorbed drop on the bed surface - low penetration time tp. If either criterion is not met, powder mixing characteristics will dominate. In the mechanical dispersion regime, the viscous or poorly wetting binder is slow to flow through the powder pores and form nuclei and good mixing is required for binder dispersion. The kinetics of nuclei formation were characterised using a simple drop penetration time test. A single drop of binder fluid was placed on a loosely packed powder bed and the time taken for the fluid to penetrate completely was measured for a range of powder and binder combinations. Loosely packed powder beds contain large macrovoids which are included in the existing Kozeny approach to estimating pore size. However it was found that these pores do not participate in liquid flow. A new two phase model was proposed where the total volume of the macrovoids was assumed to be the difference between the bed porosity and the tap porosity. A new parameter, the effective porosity eeff, was defined as the tap porosity multiplied by the estimated fraction of pores that terminate at a macrovoid and are effectively blocked pores. The pore sizes and drop penetration times were recalculated using the effective porosity and the predicted tp values were generally within an order of magnitude of the experimental results for all powders. The drop penetration time is reduced by small drops, low viscosity fluids, porous powders (but without macrovoids), large powder pores, high surface tension, low contact angle and pre-wetting of the powder bed. A new dimensionless group, the dimensionless spray flux Ya was defined to characterise the three most important operating variables in binder dispersion: liquid binder flowrate, drop size and powder flux through the spray zone. At low Ya, the majority of drops land on the powder sufficiently well separated to allow ideal “drop controlled” nucleation where one drop forms one granule. As Ya increases, the probability of drop footprints overlapping to give larger agglomerate nuclei increases. Monte-Carlo simulations were performed to validate the spray flux theory. The proportion of nuclei formed from single drops falls exponentially as Ya increases and to remain in the drop controlled regime Ya must be kept below 0.1. Analytical solutions based on the Poisson distribution for the fraction of single drop nuclei as a function of Ya were an excellent match with the Monte-Carlo data. Further validation experiments in carefully designed ex-granulator experiments and in an industrial granulator were performed. The results matched the theoretical solutions and demonstrated the ability of Ya to describe the nucleation zone in a real granulator. The proposed nucleation regime map demonstrated the interaction between drop penetration time and spray flux in nucleation. At short penetration times, such as the water and lactose system, decreasing Ya causes a shift towards the drop controlled regime and a narrower nuclei distribution. When penetration time is long, the nuclei size distribution is always larger and broader. Granulation may still be successful if the mechanical dispersion forces are able to break up the binder clumps and distribute the binder through the powder. The nucleation regime map should prove to be a useful tool for maintaining effective liquid distribution during scale-up as well as a useful trouble-shooting tool. It allows the dominant mechanism controlling the nucleation process to be easily identified using relatively simple parameters and a rational approach can then be used to control the properties of the nuclei.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "May, 2006." Includes bibliographical references (leaf 80). Online version available on the World Wide Web.

Stuttgart, Univ., Diss., 2006.

Zugl.: Mainz, Univ., Diss., 2005

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.