Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Eric M. Furst, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Eric M. Furst, Dept. of Chemical Engineering. Includes bibliographical references.

The morphology and mechanical properties of foams made out of ethylene-α-olefin copolymers (EC) having well-characterized rheological properties were investigated. The polymers differed in the amount of comonomer contained, type of comonomer and molecular weight, resulting in variable thermal properties and different rheological responses under shear and extensional flow. All of the octene-based copolymers with comparable rheological properties had similar foam morphology. However grades with low extensional viscosity and low crystallization points resulted in poor foams. Increasing density resulted in a higher secant modulus of the foamed samples. To further investigate the effects of material properties, trimethylolpropane trimethacrylate (TMPTMA) and triallyl trimesate (TAM) coagents were used to generate a series of PP derivatives through radical mediated melt state reactive modification. Coagent modification resulted in pronounced effects in the molecular weights and viscosities of the derivatives. However, evidence of long-chain branching (LCB) was only present in TAM modified PPs. Significant increases in the crystallization temperature, heat of fusion and crystallization rate were attributed to the formation of nanoparticles, which resulted in a heterogeneous nucleation effect, both for crystallization and foaming. Generally lower viscosities, coupled by strain hardening, enhanced nucleation and increased crystallization temperatures induced by the nanoparticles resulted in foams with higher expansion ratios and smaller cells, due to higher rates of cell growth, coupled with suppressed coalescence. Nanocomposites based on isotactic PP and nanosilica (SiO2) were prepared using a co-rotating twin-screw extruder (TSE) in order to investigate foaming on a larger scale. High shear stress, sufficient residence time, and high fill ratio in the melting section of the screw were the most important factors in achieving good nanosilica dispersion. Well-dispersed surface-modified hydrophobic SiO2 particles were effective nucleating agents for foaming, when used at loadings below 1 phr. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2013-01-02 11:11:07.767

I describe an experimental apparatus used to perform deformation experiments relevant to volcanology. The apparatus supports low-load, high-temperature deformation experiments under dry and wet conditions on natural and synthetic samples. The experiments recover the transient rheology of complex (melt ± porosity ± solids) volcanic materials during uniaxial deformation. The key component to this apparatus is a steel cell designed for high-temperature deformation experiments under controlled water pressure. Experiments are run under constant displacement rates or constant loads; the range of accessible experimental conditions include: 25 - 1100 °C, load stresses 0 to 150 MPa, strain rates 10⁻⁶ to 10⁻² s⁻¹, and fluid pressures 0-150 MPa. I present a suite of high-temperature, uniaxial deformation experiments performed on 25 by 50 mm unjacketed cores of porous Φ∼0.8) sintered rhyolitic ash. The experiments were performed at, both, atmospheric (dry) and elevated water pressure conditions (wet). Dry experiments were conducted mainly at 900 °C, but also included a suite of lower temperature experiments at 850, 800 and 750 °C. Wet experiments were performed at ∼650 °C under water pressures of 1, 2.5, 3, and 5 MPa, and at a fixed PH2O of ∼2.5 MPa for temperatures of ∼385, 450, and 550 °C. During deformation, strain is manifest by shortening of the cores, reduction of porosity, flattening of ash particles, and radial bulging of the cores. The continuous reduction of porosity leads to a dynamic transient strain-dependent rheology and requires strain to be partitioned between a volume (porosity loss) and a shear (radial bulging) component. The effect of increasing porosity is to expand the window for viscous deformation for dry melts by delaying the onset of brittle deformation by ∼50 °C (875 °C to 825 °C). The effect is more pronounced in hydrous melts (∼0.67 — 0.78 wt. % H₂0) where the viscous to brittle transition is depressed by ∼140 to 150 °C. Increasing water pressure also delays the onset of strain hardening due to compaction-driven porosity reduction. These rheological data are pertinent to volcanic processes where high-temperature porous magmas I liquids are encountered (e.g., magma flow in conduits, welding of pyroclastic materials).

The most known regenerated cellulosic fiber is viscose, produced in a wet spinning process, but due to cost and environmental issues other processes have been developed. Lyocell fibers, produced in air-gap spinning, have superior dry and wet strenght and a lower environmental impact compared to viscose. Research in different cellulose solvent has increased significantly tha last decadess, due to an increased cotton price and a decreased paper production, providing more wood pulp to production of regenerated cellulosic fibers.   Inorganic molten salt hydrates have the ability of dissolving cellulose for production of textile fibers. Aqueous zinc chloride was investigated at Swerea IVF from dissolution of cellulose to fiber spinning.   Aqueous zinc chloride has a dissolving capacity of up to at least 13.5 % cellulose, possibly much higher. Dissolving concentration ZnCl2/water range from 65-76 % amd lowest possible ZnCl2 concentration increases as the cellulose concentration increases. Above around 68 % ZnCl2 results in a significantly increased viscosity due to a polymeric structure formed by zinc chloride, creating a network of cellulose-zinc complexes and causing a gel behaviour of the dope difficult to use in spinning processes. The dissolving capacity of 68 % ZnCl2 is only about 8 % cellulose, which is very low compared to other solvents used today e.g. Lyocell and ILs.   Additions of 0.3 % CaCl2 or 0.05-0.1 % NaOH is used to decrease degradation of cellulose. The addition causes ans increased viscosity, which is either a result of less degradation of the interaction of the added molecules to zinc-cellulose complexes. Addition of NaOH results in a temperature dependent geleation at increased temperatures (75˚C and 80˚C), which also might be an effect of the interaction.   Highest tensile strenght was reached for wet spun fibers coagulated in ethanol of 9.5 % cellulose with 0.1 % NaOH addition, with a tenacity of 13-15 cN/tex, elongation of 10-12 % and wet strenght 30 % of dry strenght. Beacuse of many disadvantages of zinc chloride as a solvent, e.g. degradation of cellulose, corrosivity and the viscosity and gel behaviour at cellulose concentrations of 9.5 % and 13.5 % cellulose, a future possibility of a conventional production of textile fibers appears to be quite limited.

Cocoa butter is a highly complex system of triacyglycerides which has been shown to crystallize in a markedly different fashion under the application of shear. A rheometer insert was developed to enable the intact extraction of sheared samples for study of melting properties, crystal orientation and breaking stress. Samples were created by ramping from 50°C at three different cooling rates (0.5, 1 and 2°C/min) to three different end point temperatures (16, 18 and 20°C), creating nine different temperature sets. Viscosities of the cocoa butter samples under shear were recorded during sample creation and large jumps in viscosity were identified as form II and form V crystallization. Comparison of crystallization times for the nine different temperature profiles allowed for the conclusion that over a shear range of 90 – 1000 s^-1 there was no further appreciable shear acceleration of the form V transformation for the 16 and 18°C temperatures and only a slight increase up to 500 s^-1 for the 20°C temperature. Sheared samples were also examined with differential scanning calorimetry. Samples were examined for peak melting temperature on each of day 0, day 1, day 7 and day 28. Six of the nine different temperature conditions examined yielded a critical shear rate, above which the melting points of the samples were dramatically different than for low shear and no shear samples. For the day 0 and day 1 samples, above 500 s^-1 the melting temperatures were ~2°C higher than for 360 s-1 and below. For the day 7 and day 28 samples, above 500 s^-1 the peak melting temperatures were ~2°C lower than for the lower shear and no shear samples. The orientation of sheared samples was also examined using x-ray diffraction. In all of the nine temperature sets, orientation was present for shear rates of 360 s^-1 and higher. Breaking stress measurements were performed on sheared and non-sheared samples. These tests showed results remarkably similar to those seen in the DSC tests, with a critical shear rate existing in six of the nine temperature sets, above which an increase in the breaking strength occurs. Examination of samples on either side of the critical shear rate with x-ray diffraction yielded two distinct x-ray patterns leading to speculation that the application of high shear rates causes a change in the crystallization of cocoa butter leading to selective crystallization and the formation of a compositionally different form V crystal with fewer defects than its lower/no shear counterparts.

Cocoa butter is a highly complex system of triacyglycerides which has been shown to crystallize in a markedly different fashion under the application of shear. A rheometer insert was developed to enable the intact extraction of sheared samples for study of melting properties, crystal orientation and breaking stress. Samples were created by ramping from 50°C at three different cooling rates (0.5, 1 and 2°C/min) to three different end point temperatures (16, 18 and 20°C), creating nine different temperature sets. Viscosities of the cocoa butter samples under shear were recorded during sample creation and large jumps in viscosity were identified as form II and form V crystallization. Comparison of crystallization times for the nine different temperature profiles allowed for the conclusion that over a shear range of 90 – 1000 s^-1 there was no further appreciable shear acceleration of the form V transformation for the 16 and 18°C temperatures and only a slight increase up to 500 s^-1 for the 20°C temperature. Sheared samples were also examined with differential scanning calorimetry. Samples were examined for peak melting temperature on each of day 0, day 1, day 7 and day 28. Six of the nine different temperature conditions examined yielded a critical shear rate, above which the melting points of the samples were dramatically different than for low shear and no shear samples. For the day 0 and day 1 samples, above 500 s^-1 the melting temperatures were ~2°C higher than for 360 s-1 and below. For the day 7 and day 28 samples, above 500 s^-1 the peak melting temperatures were ~2°C lower than for the lower shear and no shear samples. The orientation of sheared samples was also examined using x-ray diffraction. In all of the nine temperature sets, orientation was present for shear rates of 360 s^-1 and higher. Breaking stress measurements were performed on sheared and non-sheared samples. These tests showed results remarkably similar to those seen in the DSC tests, with a critical shear rate existing in six of the nine temperature sets, above which an increase in the breaking strength occurs. Examination of samples on either side of the critical shear rate with x-ray diffraction yielded two distinct x-ray patterns leading to speculation that the application of high shear rates causes a change in the crystallization of cocoa butter leading to selective crystallization and the formation of a compositionally different form V crystal with fewer defects than its lower/no shear counterparts.

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Thesis (Ph. D.)--Lehigh University, 2004. / Includes vita. Includes bibliographical references (leaves 111-116).