In this project the design of a double base for two child restraint seats (CRS) has been developed. The objective of this project is to facilitate the transportation of two children in the rear seats of a car, maximizing the space available in the rear of the car and providing a comfortable movement to the user when placing the CRS baskets into the car. Scientific articles have been analysed providing a reference of the strength limitations and ergonomics aspects of the users as well as misuse of current CRS. Also, ergonomics and safety issues have been studied through these articles in order to fulfil with the current regulations established by the EU standards and the regulation 44 of Economic Commission for Europe. A market research and survey investigations have been done in order to study the features of existing CRS designs, opinion and needs of habitual users. The employed methodology based on a divergent and convergent design process has been carried out through different methods such as Brainstorming, 6-3-5 Method and Dark Horse Prototype in which many ideas, concepts and proposals have been developed and explained. The results of this project are shown and explained through a virtual 3D CAD model with their respective renders, explanations and technical drawings. The use and material selection of the final design are presented as well as the results of an ergonomic study performed by test with a simple physical prototype of the final design. The main outcomes of this project are included in conclusion, discussions and future work sections.

It was accidentally discovered in the 1940s that the addition of lead to double-base propellants, resulted in beneficial burn rate phenomena. However, due to its toxicity the Department of Defense has been trying to find a replacement for lead over the last decade. Research efforts with this goal in mind have generally used the same methodology of either adding different metals, using different grain sizes, or using different concentrations to obtain the same burn rate effects as lead. Although some metal oxides demonstrated significant promise, they also depleted the double-base propellant stabilizer faster than acceptable, decreasing shelf life. The research explored herein does not take the same approach, but rather attempts to replace lead and solve the stability problem at the molecular level using a novel design. The new method was to synthesize a stabilizer ligand complex with a less toxic metal to create a complex that both stabilized the propellant and provides a burn rate modifying agent. First, the synthesises of two leaded complexes, tetrakis (µ3-(4-methyl-3-nitrophenyl imido lead (II))) and bis(dinitrophenyl imido lead(II)) are reported as both a proof of concept and to determine a feasible synthetic pathway. After various unsuccessful attempts using common stabilizer molecules as ligands, n-phenylurea was identified as a suitable analogous stabilizer molecule and was bonded to a cobalt center to create hexa-1-phenylurea cobalt(II) nitrate. Additionally and serendipitously, unreported complexes of metal ions with dicyanamide were discovered, which generated a discussion between ligand strength and metal center. Each of the complexes are characterized in depth and many physical properties determined. / Chemistry

Propelentes sólidos são materiais energéticos que produzem gases em alta pressão por meio de uma reação de combustão. Qualquer propelente sólido inclui dois ou mais dos seguintes componentes: oxidante (nitratos e percloratos); combustível (resinas orgânicas ou polímeros); compostos químicos combinando oxidantes e combustíveis (nitrocelulose ou nitroglicerina); aditivos para facilitar processos de produção ou alterar a taxa de queima e inibidores (fita de etilcelulose), para restringir superfícies de combustão. Pequenas percentagens de aditivos são usadas para modificar diversas propriedades mecânicas, químicas e balísticas dos propelentes sólidos: acelerar ou desacelerar a velocidade de combustão (catalisadores e inibidores de combustão, respectivamente); assegurar a estabilidade química para prevenir a deterioração durante a estocagem; controlar as propriedades de processamento durante a produção de propelente (tempo de cura, fluidez para extrusão ou moldagem, etc.); controlar as propriedades de absorção de radiação no propelente em combustão; aumentar a resistência mecânica e diminuir a deformação elástica; e, finalmente, minimizar a sensibilidade térmica. No caso de propelentes sólidos Base Dupla (mistura de duas bases ativas: a nitrocelulose e a nitroglicerina), é possível alterar sua velocidade de queima principalmente pelo emprego de pequenos teores de modificadores balísticos, em geral sais orgânicos de cobre e chumbo. Neste trabalho, estudou-se a aceleração da velocidade de queima de uma formulação conhecida de propelente Base Dupla - BD, alterando o teor total dos modificadores balísticos cromato de cobre e estearato de chumbo (ou plastabil - nome comercial) na receita original, bem como a proporção entre eles. Estas alterações na formulação original devem, idealmente, preservar os parâmetros de desempenho estabelecidos para as propriedades químicas (estabilidade química) e mecânicas (densidade da massa e ensaios de tração), ao mesmo tempo otimizando o desempenho balístico, pelo aumento da velocidade de queima. Os resultados experimentais mostram que para os parâmetros de qualidade elongação e velocidade de queima a interação entre os fatores, Proporção Sal de Chumbo/Sal de Cobre (Fator A) e Teor de Modificadores Balísticos (Fator B) foram significativos, ou seja, quanto maior os fatores pior o resultado com as propriedades. Com os parâmetros de resistência a tração e densidade da massa, o fator A e B respectivamente influenciam negativamente quando aumentado em sua concentração. Para o parâmetro estabilidade química não houve nenhum sinal de melhora ou influencia dos fatores. No caso da velocidade de queima a interação AB é o que mais influencia. Melhorando significativamente a velocidade de queima. / Solid propellants are energetic materials which produce a considerable amount of high-pressure gases by means of a combustion reaction. Any solid propellant formulation includes at least two of the following items: oxidizer (nitrates and perchlorates); fuel (organic resins or polymers); chemical compounds combining oxidizers and fuels (nitrocellulose or nitroglycerine); additives to easy production operations or to modify the burning rate and inhibitors (tape ethyl-cellulose), to restrict the combustion surfaces. Small amounts of additives are employed to modify the mechanical, chemical and ballistic features of the solid propellants: to accelerate or diminish the burning rate (catalysts and inhibitors of burning, respectively); to assure the chemical stability in order to prevent the deterioration during stocking; to control the processing properties during propellant production (curing time, extrusion or casting rheology); to control the radiation absorption in the burning propellant; to enhance the mechanical resistance and to reduce the strain; and, finally, to get the thermal sensitivity to a minimum level. In the case of Double-Base solid propellants (blend of two energetic bases: nitrocellulose and nitroglycerine), it\'s possible to control its burning rate mainly by the use of small amounts of ballistic modifiers, generally copper and lead organic salts. This work has studied the burning rate acceleration of a known Double-Base propellant formulation, by changing the total amount of the ballistic modifiers copper chromate and lead stearate (commercially known as plastabil) in the original formulation, as well as the proportion between them. These changes at the original recipe should preserve, ideally, the performance levels required for the chemical (chemical stability) and mechanical properties (density and stress-strain evaluation), optimizing, at the same time, the ballistic performance, through the burning rate enhancement. Results show that for the parameters of quality and elongation rate of burning the interaction between factors, Proportion of Lead Salt / Salt Copper (Factor A) and content Ballistic Modifiers (Factor B) were significant, ie, the higher the worst factors result with the properties. With the parameters of tensile strength and mass density, the factor A and B respectively negatively influence increased when its concentration. For the chemical stability parameter there was no sign of improvement or influences of factors. In the case of burning rate AB interaction is what most influences. Significantly improving the speed of burning.

In this study, shelf life of three different crosslinked double base (XLDB) propellants stabilized with 2-nitrodiphenylamine (2-NDPA) and n-methyl-4-nitroaniline (MNA) were determined by using the stabilizer depletion method. Depletions of the stabilizers were monitored at different aging temperatures using High Performance Liquid Chromatography (HPLC). Kinetic models of pseudo zero, pseudo first, pseudo second and shifting order were used to find the best model equation that fits the experimental data. The rates of depletion of stabilizers were calculated at 45, 55 and 65&deg / C based on the best fit kinetic models. Using the rate constants at different temperatures, rate constants at room temperature were calculated by Arrhenius equation. The activation energies and frequency factors for the depletion of 2-NDPA and MNA were obtained for all XLDB propellants. Moreover, the results were evaluated based on the NATO standard / STANAG 4117 and the propellants were found stable according to the standard. Vacuum thermal stability (VTS) tests were also conducted to evaluate the stability of XLDB propellants. The propellant that includes the stabilizer mixture of MNA and 2-NDPA was found to have less stability than the propellants that include 2-NDPA only. However, there were rejection (puking) and migration of stabilizer derivatives for the aged samples of propellants that were stabilized with only 2-NDPA. Moreover, formation of voids and cracks were observed in block propellant samples due to excess gas generation.

Propelentes sólidos são materiais energéticos que produzem gases em alta pressão por meio de uma reação de combustão. Qualquer propelente sólido inclui dois ou mais dos seguintes componentes: oxidante (nitratos e percloratos); combustível (resinas orgânicas ou polímeros); compostos químicos combinando oxidantes e combustíveis (nitrocelulose ou nitroglicerina); aditivos para facilitar processos de produção ou alterar a taxa de queima e inibidores (fita de etilcelulose), para restringir superfícies de combustão. Pequenas percentagens de aditivos são usadas para modificar diversas propriedades mecânicas, químicas e balísticas dos propelentes sólidos: acelerar ou desacelerar a velocidade de combustão (catalisadores e inibidores de combustão, respectivamente); assegurar a estabilidade química para prevenir a deterioração durante a estocagem; controlar as propriedades de processamento durante a produção de propelente (tempo de cura, fluidez para extrusão ou moldagem, etc.); controlar as propriedades de absorção de radiação no propelente em combustão; aumentar a resistência mecânica e diminuir a deformação elástica; e, finalmente, minimizar a sensibilidade térmica. No caso de propelentes sólidos Base Dupla (mistura de duas bases ativas: a nitrocelulose e a nitroglicerina), é possível alterar sua velocidade de queima principalmente pelo emprego de pequenos teores de modificadores balísticos, em geral sais orgânicos de cobre e chumbo. Neste trabalho, estudou-se a aceleração da velocidade de queima de uma formulação conhecida de propelente Base Dupla - BD, alterando o teor total dos modificadores balísticos cromato de cobre e estearato de chumbo (ou plastabil - nome comercial) na receita original, bem como a proporção entre eles. Estas alterações na formulação original devem, idealmente, preservar os parâmetros de desempenho estabelecidos para as propriedades químicas (estabilidade química) e mecânicas (densidade da massa e ensaios de tração), ao mesmo tempo otimizando o desempenho balístico, pelo aumento da velocidade de queima. Os resultados experimentais mostram que para os parâmetros de qualidade elongação e velocidade de queima a interação entre os fatores, Proporção Sal de Chumbo/Sal de Cobre (Fator A) e Teor de Modificadores Balísticos (Fator B) foram significativos, ou seja, quanto maior os fatores pior o resultado com as propriedades. Com os parâmetros de resistência a tração e densidade da massa, o fator A e B respectivamente influenciam negativamente quando aumentado em sua concentração. Para o parâmetro estabilidade química não houve nenhum sinal de melhora ou influencia dos fatores. No caso da velocidade de queima a interação AB é o que mais influencia. Melhorando significativamente a velocidade de queima. / Solid propellants are energetic materials which produce a considerable amount of high-pressure gases by means of a combustion reaction. Any solid propellant formulation includes at least two of the following items: oxidizer (nitrates and perchlorates); fuel (organic resins or polymers); chemical compounds combining oxidizers and fuels (nitrocellulose or nitroglycerine); additives to easy production operations or to modify the burning rate and inhibitors (tape ethyl-cellulose), to restrict the combustion surfaces. Small amounts of additives are employed to modify the mechanical, chemical and ballistic features of the solid propellants: to accelerate or diminish the burning rate (catalysts and inhibitors of burning, respectively); to assure the chemical stability in order to prevent the deterioration during stocking; to control the processing properties during propellant production (curing time, extrusion or casting rheology); to control the radiation absorption in the burning propellant; to enhance the mechanical resistance and to reduce the strain; and, finally, to get the thermal sensitivity to a minimum level. In the case of Double-Base solid propellants (blend of two energetic bases: nitrocellulose and nitroglycerine), it\'s possible to control its burning rate mainly by the use of small amounts of ballistic modifiers, generally copper and lead organic salts. This work has studied the burning rate acceleration of a known Double-Base propellant formulation, by changing the total amount of the ballistic modifiers copper chromate and lead stearate (commercially known as plastabil) in the original formulation, as well as the proportion between them. These changes at the original recipe should preserve, ideally, the performance levels required for the chemical (chemical stability) and mechanical properties (density and stress-strain evaluation), optimizing, at the same time, the ballistic performance, through the burning rate enhancement. Results show that for the parameters of quality and elongation rate of burning the interaction between factors, Proportion of Lead Salt / Salt Copper (Factor A) and content Ballistic Modifiers (Factor B) were significant, ie, the higher the worst factors result with the properties. With the parameters of tensile strength and mass density, the factor A and B respectively negatively influence increased when its concentration. For the chemical stability parameter there was no sign of improvement or influences of factors. In the case of burning rate AB interaction is what most influences. Significantly improving the speed of burning.

During World War II, it was discovered that when lead was added to double-base propellants, it produced beneficial burn rate phenomena. Specifically, the propellant burn rate first increased unexpectedly at low pressures, then the burn rate became independent of pressure, followed lastly by “mesa burning” where the burn rate actually decreased with increasing pressure. This results in a beneficial negative feedback mechanism. Over the past 75 years, researchers have explored different lead complexes to achieve better propellant performance. However, over the last decade, research has shifted to finding an alternative to using lead as an additive to reduce toxicity. Until the attempts detailed herein, researchers had not, to our knowledge attempted to combine double-base propellant stabilizers with various metals to achieve these desired results. In doing so, we prepared two lead complexes, Tetrakis (µ3-(4-methyl-3-nitrophenyl imido lead (II))) 1, and Bis(dinitrophenyl imido lead(II)) 2, that were synthesized by reacting lead bis(trimethylsilyl)amide with a common double-base propellant stabilizer 2-nitrodiphenylamine (NDPA) and 4-methyl-3-nitroaniline. Both complexes formed from protolysis of the trimethylsilylamide ligand by the acidic proton of the amine, and crystallized from tetrahydrofuran (THF). Bomb calorimetry coupled with crystal density structure determined that 1 has a very high energy density of 74.1 MJ/L, more than three times the energy density of conventional nitroamine explosives, whereas 2 was lower at 38.2 MJ/L. The structure, charge and characterization of 1 and 2 are discussed. However, each complex is air sensitive making burn rate experimentation infeasible, so any possible changes to the propellant as an additive remained undetermined. Attempts to use of tin, zinc, or bismuth bis(trimethyl)amides in place of lead, were unsuccessfully characterized, although reactions were likely observed. / Chemistry

<p>Additive manufacturing of gun propellants is an emerging and promising field which addresses the limitations of conventional manufacturing techniques. Gun propellants are manufactured using wetted extrusion, which uses volatile solvents and dies of limited and constant geometries. On the other hand, additive techniques are faced with the challenges of maintaining the gun propellant’s energetic content as well as its structural integrity during high pressure combustion. The work presented in this thesis demonstrates the feasibility of producing functioning gun propellant grains using vibration-assisted 3D printing, a novel method which has been shown to extrude extremely viscous materials such as clays and propellant pastes. At first, the technique is compared to screw-driven additive methods which have been used in printing gun propellant pastes with slightly lower energetic content. In chapter two, diethylene glycol dinitrate (DEGDN), a highly energetic plasticizer, was investigated due to its potential to replace nitroglycerin in double base propellants with high nitroglycerin content. A novel isoconversional method was applied to analyze its decomposition kinetics. The ignition and lifetime values of diethylene glycol dinitrate were obtained using the new isoconversional method, in order to assess the safety of using the plasticizer in a modified double base propellant. In chapter three, a modified double base propellant (M8D) containing DEGDN was additively manufactured using VAP. The printed strands had little to no porosity, and their density was nearly equal to the theoretical maximum density of the mixture. The strands were burned at high pressures in a Crawford bomb and the burning was visualized using high speed cameras. The burning rate equation as a function of the M8D propellant as a function of pressure was obtained. Overall, this work shows that VAP is capable of printing highly energetic gun propellants with low solvent content, low porosity, with high printing speeds, and which have consistent burning characteristics at high pressures. </p>