Research on nanofluids has been undertaken for several years because of the reported enhancements of thermal properties such as thermal conductivity and enhanced heat transfer performance in laminar flow. Nanofluid is the fluid where nanoparticles are dispersed in a base fluid. Thermal conductivity and viscosity are considered to be the most prominent factors in the efficient use of nanofluids. A change in thermal conductivity and viscosity also changes the convective heat transfer coefficient. Nanoparticles can be metallic or non-metallic and also can have different shapes. In this study, Poly-Alpha-Olefin (PAO) has been used as a base fluid with Alumina (Al2O3) nanoparticles. Poly-Alpha-Olefin is commonly used for engine lubrication in military applications and cooling in electronic and industrial devices. Several nanofluid samples were made by METSS Corp. in Ohio, USA using different dispersants, different base fluids and different morphology of alumina nanoparticles. The mass fraction of nanoparticles is from 2.5 to 20 percent. The thermal properties of each sample such as thermal conductivity and viscosity have been measured. Thermal conductivity of nanofluids and pure base fluids were both measured and the thermal conductivity enhancement has been calculated. Also, the heat transfer coefficient has been determined for laminar flow under constant heat flux conditions. Results indicate that all the tested nanofluids and base fluid samples show a Newtonian behavior. Among the nanofluid samples, NF-048, which contains non-spherical Alumina nanoparticles exhibits the greatest thermal conductivity enhancement when compared to pure PAO. Heat transfer tests were conducted with pure PAO and NF-048, and an enhancement in convective heat transfer coefficient was observed. The thermal conductivity of NF-048 increases with temperature, which is consistent with heat transfer results. Furthermore, the percentage enhancement in convective heat transfer coefficient was shown to increase non-linearly with the axial distance in the heat transfer section. NF-048 exhibits a lower Re (Reynolds number)*Ra (Rayleigh number) than pure PAO under laminar flow constant heat flux conditions indicating that nanoparticle morphology and composition are the two main factors responsible for convective heat transfer enhancement at low Reynolds number.

The morphology, crystallization and melting behaviors of a series of ethylene/alpha-olefin copolymers were investigated as a function of comonomer content, comonomer type and processing conditions, including crystallization temperature and time. This was achieved by using a combination of techniques such as Nuclear Magnetic Resonance Spectroscopy (NMR), Differential Scanning Calorimetry (DSC), Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR). The results from the thermal analysis studies clearly indicated the existence of two distinct regions of crystallization, demarcated by a cross-over temperature, 𝑇*. The high temperature region (above 𝑇*) displayed cooling-rate dependence as well as significant hysteresis in crystallinity between cooling and heating processes, similar to that observed in linear polyethylene. This implied that the crystals associated with this region were formed via chain-folded lamellar growth. However, the lower temperature region (below 𝑇*) exhibited reversible changes in crystallinity between cooling and heating, and was found to be independent of the cooling rate. The temporal evolution of secondary crystallization in the copolymers was studied for times ranging from 100-106 min, at different crystallization temperatures (Tx). Two distinct melting endotherms were discerned at crystallization temperatures below 𝑇*. A higher melting endotherm that remained invariant with crystallization time (tx) was associated with lamellar crystals that were formed during primary crystallization. In contrast, both the positions as well as the magnitude of the lower temperature endotherm were found to vary systematically with log (tx). The peak positions of the low endotherm, i.e., the melting temperature of the secondary crystals, were found to consistently extrapolate to the crystallization temperature at very short times. Based on this and other considerations, the secondary crystals were associated with the melting of thin stacks of polymer chains aggregated in the form of "fringed-micelle"-like bundled crystals. The temperature dependence of the kinetic parameters (derived from Avrami and other analyses) above 𝑇* and their invariance below 𝑇*, suggested that the transformation in morphology from lamellar to bundled crystals was gradual and systematic, as the branch content was increased or as the crystallization temperature was lowered. Further verification of this result was obtained via AFM experiments. A systematic variation in morphology from lamellar to spot-like (lamellae were less clearly visible) was clearly discerned on increasing the comonomer content. Furthermore, a second morphological feature represented by bridge-like links between the lamellae, and approximately perpendicular to them, was also observed for some copolymers. This feature was correlated with the bundled crystals discussed above. The presence of an alternate crystal structure, in addition to the usual orthorhombic crystal form expected for linear polyethylene, was also established from the results of the FTIR studies. The relative proportions of the second crystal form in the copolymers as a function of branch content and temperature were modeled and estimated via mathematical deconvolution and curve-fitting processes. Comparing the results to those of the hexagonal rotator phase of n-paraffins, it was proposed that the second crystal structure in the copolymers could be assigned to a hexagonal type unit cell structure. Furthermore, the crystallization and melting behaviors of all three types of copolymers studied - ethylene/1-butene, ethylene/1-pentene and ethylene/1-hexene - were found to be identical to each other, suggesting that the crystallization process examined was independent of branch type for the ethyl, propyl and butyl branches examined. Since the lengthy butyl branch (in the ethylene-hexene copolymers) is not likely to be accommodated in the crystal, it was concluded that all three branch types were predominantly excluded from the crystal structure. Based on the results from these studies, a new model for the crystallization mechanism in these copolymers was proposed and could be further extended to other semicrystalline polymers such as PET, PEEK, PVC, PBT, i-PS and polycarbonate. In this model, the primary and secondary crystallization stages were redefined on the basis of the chain-folded lamellar growth process. According to the model, secondary crystallization involves the generation of the bundled crystals that may be viewed as physical cross-links in the amorphous phase. Therefore, it may provide a means of correlating the temporal evolution of secondary crystallization to the time and temperature dependence of the physical properties of semicrystalline polymers, above their glass transition temperatures. / Ph. D.

<p>Maleation is a common means of modification for many commodity polymers and is used to several ends. In this study, various waxes were functionalized with maleic anhydride through several maleation processes, with the end goal of obtaining a cost effective processes to make emulsifiers to be used in emulsions that impart water-resistance to building products, such as gypsum wallboards. Research was done in collaboration with an industrial partner, in order to replace commercially available emulsifiers currently being used in their processes with a less costly product that could easily be made on-site based on their consumption requirements, through a solvent-free approach. Reactions involving both the free-radical initiated maleation of paraffin waxes and thermal addition of maleic anhydride to alpha-olefins were examined extensively. It was found that emulsions with properties matching or exceeding those of control emulsion formulations were obtainable using experimental emulsifiers made through both maleation methods. When used in gypsum wallboards, emulsifiers made through thermal maleation showed levels of water-repellency that matched or exceeded those of control formulations at lower loading levels, while emulsifiers made through free-radical maleation were subject to performance issues.</p> / Master of Applied Science (MASc)

Dissociation of gas hydrates has been the primary concern of the oil and gas industry for flow assurance, mainly in an offshore environment. There is also a growing interest in the rapid formation of gas hydrates for gas storage, transport of natural gas and carbon sequestration. In this thesis, we experimentally measure the kinetics of formation and dissociation of methane hydrates and the effect of various anionic and cationic surfactants such as sodium dodecyl sulfate (SDS), cetyl trimethylammonium bromide (CTAB) and alpha olefin sulfonate (AOS) on the association/dissociation rate constants. The importance and necessity of micelle formation in these surfactants has been studied. The effect of foam generation on the rate of formation of these hydrates has also been measured. SDS was found to significantly decrease the induction time for hydrate formation. There was an added decrease in the induction time when a foamed mixture of water and SDS was used. On the other hand CTAB and AOS had an inhibiting effect. The contribution of micelles towards promoting hydrate formation was demonstrated with a series of experiments using SDS. The micelles formed by these surfactants appear to serve as nucleation sites for the association of hydrates. New experimental data is presented to show that some surfactants and the use of foam can significantly increase the rate of hydrate formation. Other surfactants are shown to act as inhibitors. A new experimental setup is presented that allows us to distinguish between surfactants that act as promoters and inhibitors for hydrate formation. / text

Nesta Dissertação, foram realizadas reações de copolimerização de 1,3-butadieno com diferentes alfa-olefinas (1-hexeno, 1-octeno e 1-dodeceno) utilizando-se um sistema catalítico do tipo Ziegler-Natta ternário constituído por versatato de neodímio, hidreto de diisobutilalumínio e cloreto de t-butila. O sistema catalítico também foi avaliado em reações de homopolimerização com cada alfa-olefina. As condições reacionais, tanto da síntese do catalisador como das reações de polimerização, foram mantidas constantes. Foi estudada a influência de diferentes teores de cada alfa-olefina (1, 3, 5, 10, 20 e 30 % em relação ao 1,3-butadieno) sobre a conversão da polimerização, a microestrutura, a massa molar, as propriedades viscosimétricas e a estabilidade térmica dos polímeros obtidos. Foi avaliada, ainda, a influência do tamanho da cadeia da alfa-olefina sobre as características da polimerização. Os polímeros foram caracterizados por espectroscopia na região do infravermelho (FTIR), cromatografia por exclusão de tamanho (SEC), viscosimetria capilar e termogravimetria (TG). A microestrutura dos polímeros, praticamente, não variou com a adição das alfa-olefinas. A massa molar numérica média (Mn) não sofreu alterações significativas, enquanto que a massa molar ponderal média (Mw) apresentou tendência ao aumento, quanto maior foi a incorporação de comonômero. A viscosidade intrínseca não apresentou uma tendência com a adição da alfa-olefina na reação, permanecendo na faixa de 2,015 a 3,557 dL/g. A estabilidade térmica do copolímero mostrou uma tendência a aumentar com a incorporação das alfa-olefinas / In this work, were performed copolymerization reactions of 1,3-butadiene with different alpha-olefins (1-hexene, 1-octene and 1-dodecene), using a ternary catalytic system of Ziegler-Natta, constituted by neodymium versatate, diisobutylaluminum hydride and t-butyl chloride. The catalytic system was also evaluated in homopolymerization reactions with the alpha-olefins. The reaction conditions, both the catalyst synthesis as the polymerization reactions, were kept constant. The influence of different content of each alpha-olefin (1, 3, 5, 10, 20 and 30% compared to 1,3-butadiene) on the polymerization conversion, the microstructure, molar mass, viscometric properties and thermal stability of polymers was studied. The influence of alpha-olefin chain size on polymerization characteristics was also evaluated. The polymers were characterized by infrared spectroscopy (FTIR), size exclusion chromatography (SEC), capillary viscometry and thermogravimetry (TG). The polymer microstructure, practically, did not change with the addition of alpha-olefins. The number average molecular mass (Mn) has not changed; while the weight average molecular mass (Mw) trended to increase. The intrinsic viscosity did not show a trend with the alpha-olefin addition, remaining in the range from 2.015 to 3.557 dL/g. The copolymer thermal stability showed a tendency to increase with the incorporation of alpha-olefins

Nesta Dissertação, foram realizadas reações de copolimerização de 1,3-butadieno com diferentes alfa-olefinas (1-hexeno, 1-octeno e 1-dodeceno) utilizando-se um sistema catalítico do tipo Ziegler-Natta ternário constituído por versatato de neodímio, hidreto de diisobutilalumínio e cloreto de t-butila. O sistema catalítico também foi avaliado em reações de homopolimerização com cada alfa-olefina. As condições reacionais, tanto da síntese do catalisador como das reações de polimerização, foram mantidas constantes. Foi estudada a influência de diferentes teores de cada alfa-olefina (1, 3, 5, 10, 20 e 30 % em relação ao 1,3-butadieno) sobre a conversão da polimerização, a microestrutura, a massa molar, as propriedades viscosimétricas e a estabilidade térmica dos polímeros obtidos. Foi avaliada, ainda, a influência do tamanho da cadeia da alfa-olefina sobre as características da polimerização. Os polímeros foram caracterizados por espectroscopia na região do infravermelho (FTIR), cromatografia por exclusão de tamanho (SEC), viscosimetria capilar e termogravimetria (TG). A microestrutura dos polímeros, praticamente, não variou com a adição das alfa-olefinas. A massa molar numérica média (Mn) não sofreu alterações significativas, enquanto que a massa molar ponderal média (Mw) apresentou tendência ao aumento, quanto maior foi a incorporação de comonômero. A viscosidade intrínseca não apresentou uma tendência com a adição da alfa-olefina na reação, permanecendo na faixa de 2,015 a 3,557 dL/g. A estabilidade térmica do copolímero mostrou uma tendência a aumentar com a incorporação das alfa-olefinas / In this work, were performed copolymerization reactions of 1,3-butadiene with different alpha-olefins (1-hexene, 1-octene and 1-dodecene), using a ternary catalytic system of Ziegler-Natta, constituted by neodymium versatate, diisobutylaluminum hydride and t-butyl chloride. The catalytic system was also evaluated in homopolymerization reactions with the alpha-olefins. The reaction conditions, both the catalyst synthesis as the polymerization reactions, were kept constant. The influence of different content of each alpha-olefin (1, 3, 5, 10, 20 and 30% compared to 1,3-butadiene) on the polymerization conversion, the microstructure, molar mass, viscometric properties and thermal stability of polymers was studied. The influence of alpha-olefin chain size on polymerization characteristics was also evaluated. The polymers were characterized by infrared spectroscopy (FTIR), size exclusion chromatography (SEC), capillary viscometry and thermogravimetry (TG). The polymer microstructure, practically, did not change with the addition of alpha-olefins. The number average molecular mass (Mn) has not changed; while the weight average molecular mass (Mw) trended to increase. The intrinsic viscosity did not show a trend with the alpha-olefin addition, remaining in the range from 2.015 to 3.557 dL/g. The copolymer thermal stability showed a tendency to increase with the incorporation of alpha-olefins

There is an increasing trend towards advancing the understanding and development of ethylene oligomerization catalysts, both in academia and industry. The metal of choice in this chemistry is invariably chromium, which has shown great versatility in selective trimerization/tetramerization, non-selective oligomerization and polymerization of ethylene. While much success has been achieved in ethylene trimerization, the same con not be said about tetramerization catalysis. Aminophosphine based ligands have demonstrated their ability towards selective 1-octene production, however, the popular PNP catalyst is able to achieve only 70% selectivity. In order to explore the possibility of developing and enhancing the selectivity of chromium based ethylene tetramerization catalyst, this thesis work was undertaken. The ligand systems we chose for our work were bidentate aminophosphine based (PN(CH2)nNP), which has yielded interesting selective oligomerization. Subtle modifications were found to result in drastic changes in selectivity, from tetramerization (PN(CH2)3NP) to trimerization (PN(CH2)2NP). We managed to successfully develop the first truly selective (over 90%) 1-octene catalyst with polymer-free behavior. Further modifications on the ligand framework, where one atom of Si was used to link the two NP units, resulted in non-selective oligomerization, in which case we determined that the oxidation-state of chromium is a key player. We explored other modifications on our selective ligands in which one of the arms on the bidentate ligand was replaced with a base-donor amine, phosphine or pyridine, and resulted in interesting selectivity changes. The final modification that we tested was a novel N(CH2)2P ligand and found it to be a highly active, non-selective oligomerization catalyst.

There is an increasing trend towards advancing the understanding and development of ethylene oligomerization catalysts, both in academia and industry. The metal of choice in this chemistry is invariably chromium, which has shown great versatility in selective trimerization/tetramerization, non-selective oligomerization and polymerization of ethylene. While much success has been achieved in ethylene trimerization, the same con not be said about tetramerization catalysis. Aminophosphine based ligands have demonstrated their ability towards selective 1-octene production, however, the popular PNP catalyst is able to achieve only 70% selectivity. In order to explore the possibility of developing and enhancing the selectivity of chromium based ethylene tetramerization catalyst, this thesis work was undertaken. The ligand systems we chose for our work were bidentate aminophosphine based (PN(CH2)nNP), which has yielded interesting selective oligomerization. Subtle modifications were found to result in drastic changes in selectivity, from tetramerization (PN(CH2)3NP) to trimerization (PN(CH2)2NP). We managed to successfully develop the first truly selective (over 90%) 1-octene catalyst with polymer-free behavior. Further modifications on the ligand framework, where one atom of Si was used to link the two NP units, resulted in non-selective oligomerization, in which case we determined that the oxidation-state of chromium is a key player. We explored other modifications on our selective ligands in which one of the arms on the bidentate ligand was replaced with a base-donor amine, phosphine or pyridine, and resulted in interesting selectivity changes. The final modification that we tested was a novel N(CH2)2P ligand and found it to be a highly active, non-selective oligomerization catalyst.

There is an increasing trend towards advancing the understanding and development of ethylene oligomerization catalysts, both in academia and industry. The metal of choice in this chemistry is invariably chromium, which has shown great versatility in selective trimerization/tetramerization, non-selective oligomerization and polymerization of ethylene. While much success has been achieved in ethylene trimerization, the same con not be said about tetramerization catalysis. Aminophosphine based ligands have demonstrated their ability towards selective 1-octene production, however, the popular PNP catalyst is able to achieve only 70% selectivity. In order to explore the possibility of developing and enhancing the selectivity of chromium based ethylene tetramerization catalyst, this thesis work was undertaken. The ligand systems we chose for our work were bidentate aminophosphine based (PN(CH2)nNP), which has yielded interesting selective oligomerization. Subtle modifications were found to result in drastic changes in selectivity, from tetramerization (PN(CH2)3NP) to trimerization (PN(CH2)2NP). We managed to successfully develop the first truly selective (over 90%) 1-octene catalyst with polymer-free behavior. Further modifications on the ligand framework, where one atom of Si was used to link the two NP units, resulted in non-selective oligomerization, in which case we determined that the oxidation-state of chromium is a key player. We explored other modifications on our selective ligands in which one of the arms on the bidentate ligand was replaced with a base-donor amine, phosphine or pyridine, and resulted in interesting selectivity changes. The final modification that we tested was a novel N(CH2)2P ligand and found it to be a highly active, non-selective oligomerization catalyst.

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