The tire-terrain interaction is complex and tremendously important; it impacts the performance and safety of the vehicle and its occupants. Icy roads further enhance these complexities and adversely affect the handling of the vehicle. The analysis of the tire-ice contact focusing on individual aspects of tire construction and operation is imperative for tire industry's future. This study investigates the effects of the tread rubber compound on the drawbar pull performance of tires in contact with an ice layer near its melting point. A set of sixteen tires of eight different rubber compounds were considered. The tires were identical in design and tread patterns but have different tread rubber compounds. To study the effect of the tread rubber compound, all operational parameters were kept constant during the testing conducted on the Terramechanics Rig at the Terramechanics, Multibody, and Vehicle Systems laboratory. The tests led to conclusive evidence of the effect of the tread rubber compound on the drawbar performance (found to be most prominent in the linear region of the drawbar-slip curve) and on the resistive forces of free-rolling tires. Modeling of the tire-ice contact for estimation of temperature rise and water film height was performed using ATIIM 2.0. The performance of this in-house model was compared against three classical tire-ice friction models. A parametrization of the Magic Formula tire model was performed using experimental data and a Genetic Algorithm. The dependence of individual factors of the Magic Formula on the ambient temperature, tire age, and tread rubber compounds was investigated. / Master of Science / The interaction between the tire and icy road conditions in the context of the safety of the occupants of the vehicle is a demanding test of the skills of the driver. The expected maneuvers of a vehicle in response to the actions of the driver become heavily unpredictable depending on a variety of factors like the thickness of the ice, its temperature, ambient temperature, the conditions of the vehicle and the tire, etc. To overcome the issues that could arise, the development of winter tires got a boost, especially with siping and rubber compounding technology. This research focuses on the effects on the tire performance on ice due to the variation in the tread rubber compounds. The experimental accomplishment of the same was performed using the Terramechanics rig at the Terramechanics, Multibody, and Vehicle Systems (TMVS) laboratory. It was found that the effect of the rubber compound is most pronounced in the region where most vehicles operate under normal circumstances. An attempt was made to simulate the temperature rise in the contact patch and the water film that exists due to the localized melting of ice caused by frictional heating. Three classical friction models were used to compare the predictions against ATIIM 2.0, an in-house developed model. Using an optimization technique namely the Genetic Algorithm, efforts were made to understand the effects of the tread rubber compound, the ambient temperature, and the aging of the tire on the parameters of the Magic Formula model, an empirical model describing the performance of the tire.

A major challenge in tire research, is tire wear modeling. There are too many factors affecting tire wear, and part of those factors are difficult to be accurately expressed in physics and math. The objective of this research is to develop a machine learning based rubber sample wear model, and find the correlation between sample wear and tire wear. To develop this model, accurate and diverse wear data is necessary. The Dynamic Friction Tester (DFT) was designed and built for this purpose. This test machine has made it possible to collect accurate rubber sample wear data which has been validated under different conditions. Wear tests under diverse test conditions were conducted, and the test data were used to train machine learned based wear models with different algorithms, such as Neural Networks and Support Vector Machines. With test-proved wear behavior classification as additional input, and feature selection, performance of the trained rubber sample wear model has been further improved. To correlate rubber sample wear and tire wear, a set of correlation functions were developed and proposed. By validating the correlation functions using tire wear test data collected on roads, this research contributes a fast and economical approach to predict tire wear. / Doctor of Philosophy / Tire wear is closely related to the life time of tire, and excessive wear of tire can results in serious accidents. Since 1950s, research have been done to predict tire wear using experiments and empirical relations. These approaches are expensive, time consuming, and highly restricted to certain conditions. The objectives of this research is to develop a statistic based rubber sample wear model, and find the correlation between rubber sample wear and tire wear. To develop the statistic based rubber sample wear model, a test machine, named Dynamic Friction Tester (DFT) was designed and built to collect rubber sample wear data. The final rubber sample wear model is trained by wear data under 600 different test conditions. A set of mathematical equations were proposed to correlate rubber sample wear and tire wear. These equations were validated by actual tire wear data collected from lab and public roads. In combination of the statistic based rubber sample wear model and mathematical relation between rubber sample wear and tire wear, this research contributes a flexible, economical, and fast method to predict tire wear.

Yes / Natural rubber (NR) and crosslinked polyethylene (XLPE) waste streams were devulcanized by solid state shear milling (S3M), producing a fine powder that may be more easily reprocessed. Understanding devulcanization and the nature of decrosslinked thermoset materials is of utmost importance for turning these waste steams into functional products. It was found that the devulcanized powders contained significant concentrations of radicals, which may be active in the subsequent revulcanization process. The produced devulcanized powders were converted into recyclable thermoplastic vulcanizates (TPVs) by twin screw extrusion. Reprocessing of these powders into value-added products is an important step in recycling and the use of extrusion allows for high throughput and industrial viability. Herein, we demonstrate that the optimal conditions for reprocessing are dependent upon the particle size of the devulcanized powder. Furthermore, dynamic vulcanization is affected by the nature of these recyclate powders. The successfully prepared TPVs showed similar properties to virgin materials, with a high elongation to failure. Therefore, the conversion of waste rubber into the rubber phase of a TPV shows significant promise in moving towards sustainable products, providing the revulcanization step can be well controlled. / EPSRC and NSFC for their funding of this work through the Joint UK-China Low Carbon Manufacturing Grant, Grant number EP/S018573/1.

Wheat gluten, wheat gliadin, and corn zein agricultural proteins were evaluated as multifunctional additives that: (1) provided reinforcement, (2) improved thermal stability, and (3) lowered the cost of polymer composites. Wheat proteins were utilized in two polymer matrices: poly(vinyl alcohol) (PVA) and synthetic cis-1,4-polyisoprene rubber (IR). The proteins were hydrolyzed and dispersed in the polymer matrix, where they cooperatively self-assembled into nanostructures called amyloids. Amyloids have the potential for high rigidity and stability due to high β-sheet content. In Chapter II, trypsin hydrolyzed wheat gluten (THWG) proteins were incubated in aqueous PVA solutions, then the composite solutions were air dried and compression molded into films. Anisotropic protein aggregates formed through a typical mechanism of β-sheet self-assembly, where a greater molding time and pressure and/or a lower PVA molecular weight allowed for more protein aggregation. The larger protein structures provided less reinforcement. In Chapters III and IV, THWG and trypsin hydrolyzed gliadin (THGd), a component protein in wheat gluten, were compounded in synthetic polyisoprene rubber to form nanocomposites. The reinforcement correlated to the protein β-sheet content and varied with protein concentration, protein batch preparation, processing temperature, and compounding time. The isotropic β-sheet containing structures were very thermally stable, even under harsh rubber compounding conditions. By optimizing the processing parameters uniform protein dispersion and optimal IR reinforcement were achieved, although the protein and IR phases had poor compatibility. In Chapter V, the THGd-IR composites were cured using a typical cure package and molding process. Protein aggregation into nanostructured β-sheets was observed during the curing process. Rubber reinforcement increased as a function of protein concentration and curing time. In Chapter VI, a hydrophobic protein (zein) was substituted for the hydrophilic protein (gliadin) used previously to improve protein-IR compatibility. The zein protein was better at reinforcing IR, while gliadin improved mechanical stability. Both zein and gliadin improved the thermal stability of IR. The results from Chapters II-VI showed an interesting concept: in situ filler formation in polymer matrices where the choice of protein, polymer, and processing conditions influenced the final morphology and composite properties. / Doctor of Philosophy / We use plastics every day for a wide range of applications, from food packaging to automobile tires. Many of these plastics are composite materials, called “polymer composites,” meaning they are made of two or more chemically distinct materials where one material is a polymer. For reference, a polymer is a long chain molecule made of many (“poly-”) units (“- mer”). Polymer composites often contain additives which modify the properties of the polymer. For example, many soft polymers, such as tire rubber, need to be made stiffer and so a “reinforcing additive” is used to improve the stiffness of the rubber. Many composite materials are made stiffer so less material can be used. This process is called “lightweighting.” The automotive industry and food packaging industry use this process to reduce weight and fuel costs. In this research, plant proteins are tested as reinforcing additives in polymer composites. Plant proteins, such as wheat gluten, are abundant, non-toxic, sustainable, and can self-assemble into extremely small, stiff structures. For these reasons, plant proteins offer an environmentally friendly alternative to typical reinforcing additives. This dissertation shows that plant proteins can reinforce two polymers with very different properties. The first polymer is poly(vinyl alcohol) (PVA), which is biodegradable, hydrophilic (i.e., “water loving”), and is commonly used in flexible food packaging. The second polymer is synthetic cis-1,4-polyisoprene rubber (IR), which is non-biodegradable, hydrophobic (i.e., “water fearing”), and is commonly used in automotive tires. In Chapters II-V, the wheat gluten protein is hydrolyzed, i.e., chemically “chopped” into short chain peptides, to encourage the self-assembly of the plant protein into small, stiff structures. The self-assembled protein structures survive typical industrial processing techniques, such harsh rubber compounding conditions which involve high heat, pressure, and shear forces (i.e., the material is pushed in opposing directions). In Chapter VI, full corn and wheat proteins are incorporated into IR using standard industrial mixing and curing processes. The corn and wheat proteins reinforce the synthetic rubber and inhibit the degradation of the chemical structure of cured rubber under high heat. At certain protein concentrations, the proteins improve the elasticity and lessen the permanent deformation in the polymer composite. Together, Chapters II-VI show that proteins from diverse plant sources can be used to improve the performance of polymers with dissimilar properties.

In recent years the use of inflatable dams has become more widespread throughout the world. Various people have done studies on the shape and membrane tension of these structures; however, only a few authors have considered dynamic behavior. Due to the nature of the applications and the material composition of these structures, a study considering the dynamic response of an inflatable dam is warranted. In this study, the equation of motion for an air-inflated dam is derived, then solved using the Galerkin approximation method. The solution is performed for a one-term approximation and a two-term approximation, where both solutions use a sine function to approximate the deflected shape of the dam. Frequencies and amplitudes are calculated and presented in tables and plots for the first four modes, and three different values of the central angle of the dam. Comparisons to the results of other studies are presented at the conclusion of this study. / Master of Science

A complex permittivity measurement system composed of a network analyzer and a open-ended coaxial waveguide has been used to evaluate the permittivity of rubber samples. The conductivity of rubber provides an indication of the dispersion of carbon black throughout the rubber matrix. The technique is based on the Deschamps antenna modeling theorem which relates the effective admittance of an antenna in some arbitrary medium to the effective admittance of the same antenna embedded in free space. This technique is well suited for material with loss tangents between 0.1 and 1.0. Only material within a radius on the order of the outer conductor radius of the coaxial waveguide is interrogated. Inferred permittivity measurements for rubber samples are presented. An APC-7 connector is used as the transducer which provides a means for convenient calibration because standard calibration terminations can be used. The amount of pressure from the sample applied to the waveguide affects reflection coefficient measurements, preventing consistent results. / Master of Science

Tank track pads have been known to degrade rapidly under adverse conditions, especially during cross country service where the average life has been estimated to be 500 miles. Several factors have been identified as being the cause for such low service life. One of these is the 'quality of dispersion' which plays an important role in the performance of any rubber compound. In order to evaluate the effect of the quality of dispersion on the service life of rubber compounds, a controlled blending experiment was carried out with a recipe modeled on a standard track pad formula. Mechanisms of failure produced by a bad dispersion have been identified. Two interesting observations were made, one of which was the formation of voids and the other was crack propagation along flow lines which are directly relatable to processing conditions. / Master of Science

A reciclagem de materiais poliméricos tem sido objeto de estudos a fim de poupar recursos naturais, principalmente de fontes não renováveis, com objetivo de minimizar os impactos causados ao meio ambiente. Nesse cenário, aparecem os materiais elastoméricos, como a borracha, principalmente na utilizada da fabricação de pneus, uma vez que a indústria pneumática consome aproximadamente 60% da produção de borracha. Como a destinação final de forma ambientalmente correta do pneu é uma exigência devidamente amparada por normas e leis nacionais e internacionais, o objetivo desse trabalho é desenvolver um estudo sobre a eficácia das irradiações das micro-ondas no processo de desvulcanização do pó de pneu. Para esse estudo as amostras de pó de pneu foram submetidas a irradiações de micro-ondas, e posteriormente incorporadas às matrizes poliméricas de NR (borracha natural) e SBR (borracha de butadieno-estireno), e caracterizadas para verificação de suas propriedades. Para caracterização das amostras foram utilizados os seguintes ensaios: Espectroscopia no Infravermelho (FTIR), Dureza, Resistência à Tração e Alongamento, Reometria, Índice de Inchamento, Análise Termogravimétrica (TGA) e Microscopia Eletrônica de Varredura (MEV). Verificou-se viabilidade técnica da incorporação do pó de pneu nas matrizes de NR e SBR, uma vez que alguns resultados mostraram que a adição do pó de pneu irradiado via micro-ondas não ocasionou perdas significativas nas propriedades mecânicas e térmicas dos compostos. / The recycling of polymeric materials has been studied in order to save natural resources, mainly from non-renewable sources, in order to minimize the impacts caused to the environment. In this scenario, there are elastomeric materials, such as rubber, mainly used in tire manufacturing, since the pneumatic industry consumes approximately 60% of rubber production. As the final destination of an environmentally correct tire is a requirement, duly supported by national and international laws and regulations, the objective of this work is to develop a study on the efficiency of microwave irradiation in the process of tire powder devulcanization. For this study the tire powder samples were subjected to microwave irradiation, and later incorporated into the polymer matrices of NR (natural rubber) and SBR (butadiene-styrene rubber), and characterized for verification of their properties. For characterization of the samples the following tests were used: Infrared Spectroscopy (FTIR), Hardness, Tensile Strength and Stretching, Rheometry, Swell Index, Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (MEV). It was verified the technical feasibility of the incorporation of the tire powder in the NR and SBR matrices, since some results showed that the addition of the tire powder irradiated by microwave did not cause significant losses in the mechanical and thermal properties of the compounds.

Os estudos da epizootiologia foram realizados em Pindorama-SP e em Itiquira-MT durante dois anos. No primeiro local, constatou-se em agosto de 1998 uma epizootia de Sporothrix sp. em ninfas do percevejo. Em Itiquira, quando a infestação atingiu 56 ninfas e 18 adultos/folha, verificou-se a ocorrência natural de Sporothrix sp., reduzindo significativamente a população. Na seleção de fungos entomopatogênicos, testou-se sessenta isolados obtidos de diferentes hospedeiros e localidades sobre ninfas do 4º ínstar. Os melhores isolados foram B. bassiana (619 e 1196) com 56 e 84% de mortalidade com 3 dias após a inoculação, M. anisopliae (1144 e 1104) ambos com 90%, S. insectorum (1229) com 92% e P. fumosoroseus (1200) com 100%. Trichoderma sp., após quatro dias da inoculação causou 78% de mortalidade. Na avaliação de campo, as concentrações superiores a 10 12 e 10 13 conídios/ha foram eficientes para controle do percevejo sendo que os fungos P. fumosoroseus (1200), B. bassiana (447) e M. anisopliae (1175 e 1144) foram eficientes para controle de L. heveae. Nos estudos de toxicidade, as formulações Decis e Nuvacron foram compatíveis com B. brongniartii (619). A maioria das combinações, com exceção da formulação de Decis foi compatível com V. lecanii (972). M. anisopliae (1144) foi muito sensível para todas as formulações. Nuvacron e Stron foram compatíveis com B. bassiana (1196), P. fumosoroseus (1200) e S. insectorum (1229). Marshal foi compatível com B. bassiana (1196) e S. insectorum (1229) e Dipterex foi compatível com P. fumosoroseus (1200). Avaliou-se dois métodos de produção e dois meios de cultura para os fungos B. bassiana (1196), M. anisopliae (1189), Sporothrix insectorum (1229), Paecilomyces fumosoroseus (1200) e Verticillium lecanii (1200). Os fungos P. fumosoroseus e B. bassiana foram os que mais produziram pelo método da caixa. No método da bandeja, B. bassiana foi o fungo mais produtivo. Entre os métodos de produção testados V. lecanii produziu mais no método de bandeja e P. fumosoroseus no método da caixa. Em observações em Microscópio Eletrônico de Varredura LEO 435VP (MEV) verificou-se que em geral, todos os hifomicetos apresentaram ciclos biológicos semelhantes sobre L. heveae, tendo um período de adesão, germinação e início da penetração de 24 h, crescimento vegetativo entre 48 e 72 h, e a extrusão e conidiogênse dos patógenos em 96 h. / Studies on epizootiology were carried out in Pindorama-SP and Itiquira-MT, Brazil during two years. In Pindorama, in August 1998 an epizootic of Sporothrix sp. was observed in lacebug nymphs. In Itiquira, when the infestation reached 56 nymphs and 18 adults/leaf, a natural occurrence of Sporothrix sp. was observed, reducing significantly the pest population. Entomopathogenic fungi for use in lacebug control were selected from sixty isolates obtained from different hosts and applied to 4th instar nymphs. The best isolates were Beauveria bassiana (619 and 1196) with 56 and 84% mortality 3 days after the inoculation, Metarhizium anisopliae (1144 and 1104) both with 90%, S. insectorum (1229) with 92%, and Paecilomyces fumosoroseus (1200) with 100%. Trichoderma sp. caused 78% of mortality four days after inoculation. In field evaluations, the concentrations above 10 12 conidia/ha were efficient for control of the lacebug and the fungal isolates P. fumosoroseus (1200), B. bassiana (447) and M. anisopliae (1175 and 1144) were efficient for control of L. heveae. In the toxicity studies, the formulations Decis and Nuvacron were compatible with B. brongniartii (619). Most of the combinations, except for Decis, were compatible with Verticillium lecanii (972). M. anisopliae (1144) was very sensitive to all the formulations. Nuvacron and Stron were compatible with B. bassiana (1196), P. fumosoroseus (1200) and S. insectorum (1229). Marshal was compatible with B. bassiana (1196) and S. insectorum (1229), and Dipterex was compatible with P. fumosoroseus (1200). Two production methods and two culture media were evaluated for production of the fungi B. bassiana (1196), M. anisopliae (1189), S. insectorum (1229), P. fumosoroseus (1200) and V. lecanii (1200). The fungi P. fumosoroseus and B. bassiana were the most productive using the box method. In the tray method, B. bassiana was the most productive fungus. Between the production methods tested, V. lecanii was more productive in the tray method and P. fumosoroseus in the box method. Observations in Scanning Electronic Microscope LEO 435VP (SEM) revealed that, in general, all of the hyphomycetes had similar biological cycles on L. heveae, with adhesion, germination and beginning of the penetration within 24 h, vegetative growth between 48 and 72 h, and the extrusion and conidiogenesis of the pathogens by 96 h.

Este trabalho apresenta estudo sobre a viabilidade técnica da incorporação de borracha de pneus em ligantes asfálticos utilizados em obras de pavimentação. Trata-se de uma alternativa para solucionar um grave problema ambiental, pois no Brasil, anualmente, são descartados mais de 30 milhões de pneus, dos quais a maior parte é disposta em locais inadequados, servindo para a procriação de vetores de doenças e representando risco de contaminação do meio-ambiente. Os efeitos dos principais fatores que condicionam o comportamento do ligante asfalto-borracha (teor e granulometria da borracha, temperatura de mistura, tempo de reação) são avaliados através de ensaios tradicionais de caracterização de ligantes asfálticos e também ensaios do Método Superpave, que determinam propriedades fundamentais, diretamente relacionadas ao desempenho dos pavimentos no campo. Os resultados da análise estatística da programação fatorial de ensaios laboratoriais desenvolvida evidenciam o efeito preponderante do teor de borracha e, principalmente, que o ligante asfalto-borracha pode aumentar a resistência ao acúmulo de deformação permanente e ao aparecimento de trincas por fadiga do revestimento. / This work presents the results of a study about the technical feasibility of the use of asphalt-rubber binder by the asphalt paving industry. In Brazil, more than 30 million tires a year are disposed, mostly in inadequate sites, causing serious health and environmental problems. The effects of the main factors (rubber content, rubber particle size, temperature of mixture, reaction time) on the behavior of asphalt-rubber binders are evaluated by traditional tests and also by tests of the Superpave Method, which are based on fundamental properties, directly related to field performance. The results of the statistical analysis of the factorial design of laboratory experiments show the most significant effect of rubber content and, mainly, that asphalt-rubber binder can increase the resistance to permanent deformation and fatigue cracking.