O poli(cloreto de vinila) PVC é o segundo termoplástico mais consumido no mundo devido a sua versatilidade e seu amplo espectro de utilização. O desenvolvimento de modelos matemáticos representativos é de grande importância para o projeto, análise e otimização de processos de polimerização. A determinação das condições de operação ótimas para um reator de polimerização levando em conta as restrições operacionais e de qualidade do polímero produzido poderia, em princípio, ser realizada de maneira empírica. Entretanto, pode ser feita de maneira muito mais eficiente, econômica e segura através da solução de um problema de otimização. Para tanto, é imprescindível dispor de um modelo matemático representativo do processo de polimerização, confiável e validado experimentalmente em condições tão amplas quanto possível. Dentro deste panorama, o presente trabalho buscou desenvolver, a partir de modelos previamente descritos na literatura, um modelo matemático do processo de polimerização em suspensão de cloreto de vinila. Parâmetros do modelo referentes às limitações difusionais das constantes de terminação e propagação foram ajustados. As previsões do modelo foram comparadas com dados experimentais obtidos na literatura, referentes a diferentes tipos de iniciador, e diferentes condições operacionais. Verificou-se que o modelo desenvolvido foi capaz de representar adequadamente todos os dados experimentais testados quando ajustado individualmente para cada ensaio. Quando aplicada uma correlação generalizada para os parâmetros ajustáveis, o modelo representou de forma satisfatória, tanto qualitativa como quantitativamente, a maioria dos dados experimentais. As possíveis causas para as discrepâncias encontradas em alguns casos foram discutidas e recomendações para melhoramento do modelo foram apresentadas. / Poly (vinyl chloride) PVC is the second-largest thermoplastic that is consumed in the world because of its versatility and comprehensive series of application. The development of representative mathematical models is important for the design, analysis and optimization of polymerization processes. The determination of the optimal operational conditions for a polymerization reactor taking into account operational constraints and quality of the polymer produced could be, in principle, achieved by empirical trial-and-error procedure. However, this can be made in a much more efficient, economic, and safe way through the solution of an optimization problem for which it is required a representative mathematical model of the polymerization process. Such model should be reliable and validated over as wide a range of experimental conditions as possible. In this scenario, the objective of the present work was to develop a mathematical model for suspension polymerization of vinyl chloride, with the abovementioned features, from the models previously described in literature. Model parameters for the diffusion-controlled termination and propagation rate constant were estimated. The model predictions were compared with experimental data taken from the literature, covering different kinds of initiators and different operational conditions. It was found that the model was able to suitably represent all the experimental data tested when fitted for each run. When a general correlation for the adjustable parameters was obtained and included in the model, the model predictions reproduced satisfactorily most of the experimental data in both qualitative and quantitative fashions. Possible causes for the discrepancies found in some cases were discussed and recommendations for model improvement were suggested.

Made available in DSpace on 2014-06-12T23:15:38Z (GMT). No. of bitstreams: 2 arquivo7432_1.pdf: 2032621 bytes, checksum: 08207254498102f66498fd2876c20c69 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / Faculdade de Amparo à Ciência e Tecnologia do Estado de Pernambuco / A importância de fazer uma blenda, que é uma tecnologia relativamente recente, está associada ao fato de seu desenvolvimento ser menos oneroso do que o desenvolvimento de novos materiais por meio de métodos de síntese. Nesse estudo foi utilizada a blenda de poli(cloreto de vinila)/poliestireno (PVC/PS), nas composições 95/05, 90/10, 70/30, 50/50 e 30/70. Com o objetivo de estudar a miscibilidade da blenda PVC/PS, empregando as técnicas de viscosimetria pelos modelos de Krigbaum-Wall, Garcia et al. e Pan et al. em solução; espectroscopia no infravermelho com transformada de Fourier (FT-IR), índice de refração e microscopia eletrônica de varredura (MEV), foram igualmente utilizadas. Embora a análise de miscibilidade por viscosimetria seja de fácil execução, os resultados da blenda PVC/PS mostraram-se diferentes, quando foram comparados os três modelos propostos. O modelo de Pan et al. foi o que mais se aproximou dos resultados obtidos, junto às técnicas de FT-IR e índice de refração, onde o resultado foi de imiscibilidade da blenda PVC/PS em toda a sua extensão. Por outro lado, quando as blendas foram irradiadas, o PS comportou-se como agente radioprotetor da matriz do PVC, devido a dissipação de boa parte de energia absorvida na ressonância existente no interior dos anéis aromáticos. O fator de proteção do PS foi calculado em 78 e 70% para as proporções de 95/05 e 90/10, respectivamente. A radiação gama, na dose de 50 kGy, também atuou no sistema como agente compatibilizante na blenda de composição 95/05. Mudanças nas propriedades mecânicas dos filmes de PVC, PS e nas blendas PVC/PS, na dose de esterilização (25 kGy) também foram observadas neste estudo

[pt] O PVC é o único polímero de grande consumo que não é 100% originário do petróleo, pois contêm, em peso, 57% de cloro (derivado do cloreto de sódio - sal de cozinha) e apenas os restantes 43% de eteno são derivados do petróleo. Como as matrizes ricas em cloro são privilegiadas para aplicações em meios ambientes ricos em bactérias, tais como dutos enterrados ou imersos em água do mar, o PVC já vem sendo usado em diversas aplicações na área de transporte de fluidos, notadamente água, mas pode ser considerado também uma alternativa para o transporte de outros fluidos. Assim sendo este trabalho estuda o efeito físico - químico do envelhecimento do poli (cloreto de vinila) – PVC, utilizando amostras em pó, expostas a diversos fluidos (água, etanol e diesel), por diversos períodos de tempo. A primeira parte do trabalho consistiu na caracterização do material como recebido e a segunda na caracterização do material após exposição aos fluidos. As técnicas de caracterização utilizadas foram termogravimetria (TGA), termogravimetria diferencial (DTGA), calorimetria diferencial de varredura (DSC), métodos espectroscópicos (FTIR-ATR) e de Difração de Raios X, que permitiram avaliar a interação físico-química dos diversos fluidos com o PVC. Os resultados obtidos mostraram que a morfologia do PVC não foi afetada pelo envelhecimento, também indicam que e possível a difusão dos fluidos dentro da matriz polimérica. / [en] The PVC is the unique polymer of great consume that is not 100% derived from oil, because it contains, by weight, 57% chlorine (derived from sodium chloride - table salt) and only the remaining 43% of ethylene is derived from oil. As the matrix rich in chloride is preferred for applications in media environments rich in bacteria, such as pipelines buried or immersed in sea water, the PVC is being used in various applications in the transport of fluids, especially water, but can be also considered an alternative for the transport of other fluids. Thus this work studies the physical - chemical effect aging of poly (vinyl chloride) - PVC, using powder samples exposed to various fluids (water, ethanol and diesel) for various periods of time. The first part of the work was to characterize the material as received and the second the characterization of the material after exposure to fluids. The characterization techniques used were thermogravimetry (TGA), differential thermogravimetry (DTGA), differential scanning calorimetry (DSC), spectroscopic methods (FTIR-ATR) and X-ray diffraction, to measure the physico-chemical interaction of different fluids with PVC. The results showed that the morphology of PVC was not affected by aging, and it can also indicate the diffusion possibility of fluid within the polymer matrix.

This thesis is focused on the construction of punching device for punching continuously extruded plastic profile. This device is part of a larger production line. The theoretical part of this work will be focused in an introduction to plastic extrusion, cutting, molding properties and market research with punched plastic profiles. The practical part will deal with the product description, production line and the structural design of the entire machine itself including calculations. Part of this work are also drawing of selected parts and a 3D model.

Wetlands in densely urbanized landscapes display altered physical, chemical, and biological features; however, long term trends in these are poorly known. The purpose of this study was to determine if biological, physical, and chemical changes in isolated cypress domes are related to time since incorporation within an urban landscape. Sixteen cypress domes in Tampa, Florida were placed into four decadal age groups based on construction date of residential homes within 200 m of wetland edge, with multiples in each age group: 1970s, 1980s, 1990s, 2000s, and rural sites as regional controls. Each site was visited monthly from July 2008 until July 2009. Hylid treefrogs were monitored using PVC refugia and mating calls. Non-hylid anuran species were monitored using mating call surveys and pitfall traps. Hydrology, pH, and conductivity were recorded, transects were made once at each site from wetland center to terrestrial edge in all four cardinal directions, and all trees greater than 8cm DBH were identified and measured for basal area. The dominant treefrog captured was the exotic O. septentrionalis, which was significantly more abundant in 1990s urban cypress domes than either rural sites or other urban decadal groups. The number of both the exotic O. septentrionalis and the native H. cinerea were positively correlated to more recent decades of development surrounding wetlands. H. squirella was detected at sites where O. septentrionalis was rare, and H. femoralis was found almost exclusively at rural sites. Hydroperiods of all urban cypress domes were three times longer on average than rural sites, and conductivity was significantly elevated at all urban sites. In cypress domes within the 1970s decade group, the relative abundance of Florida "facultative wet" tree species was greater than "obligate wet" tree species suggesting encroachment of Acer rubrum into cypress domes possibly due to decades of fire exclusion. At these long isolated sites exotic plants such as Sapium sebiferum were most abundant. Results indicate rapid changes in both physico-chemical characteristics and anuran composition, and long term effects of decreased treefrog abundance and altered tree community structure following incorporation within the urban landscape.

Plasten Polyvinylklorid har under lång tid kritiserats ur miljösynpunkt på grund av plastens hälsofarliga beståndsdelar. PVC har medfört enorma miljöskador på ozonskiktet som orsakats av klorfluorkolväten men det som framförallt varit bekymrande på senare tid är mjukningsmedel som har skapat oro över deras möjliga hormonstörande effekter. Detta har medfört en politisk osäkerhet och otrygghet för företag som arbetar med PVC. Företaget HRD Carpets AB önskar utveckla ett alternativt ersättningsmaterial för PVC plastmattor och ser helst fram emot en biobaserad lösning. Syftet med denna studie är att finna ett lämpligt ersättningsmaterial för PVC plastmattor. Målet har varit att genomföra en studie som ger underlag för ett alternativt ersättningsmaterial som går att vidareutveckla i form av fortsatta studier. Kravspecifikationen har varit utgångspunkten i denna studie för att finna ett lämpligt ersättningsmaterial. De mekaniska egenskaperna för PVC plasten som används i fabriken har identifierats och tolkats genom ett dragprovningstest som genomförts. Dessa egenskaper har varit de elementära kraven tillsammans med övriga krav som framgår i kravspecifikationen. I denna studie undersöks alternativa biomaterial samt syntetiska material. Med hjälp utav programvaran Cambridge Engineering Selector har ett urval av material tagits fram och undersökts genom en urvalsprocess. Genom intervjuer, publikationer, journaler och litteraturer har biobaserade alternativ undersökts. Resultatet visade att den syntetiska plasten Polybutylentereftalat (PBT) tillsammans med färgämnen uppfyller de basala krav för det tillämpningsområdet som undersöks. Resultatet visade att biomaterialet Polymjölksyra (PLA) och Polybutensuccinat (PBS) uppfyller samtliga krav och kan lämpa sig som alternativa lösningar. Dessa material har dock en kort livslängd och att öka materialets hållbarhet är en utmaning med dessa biomaterial. / The Polyvinyl chloride (PVC) has been criticized from an environmental point of view due to the plastic's hazardous components for a long time. PVC has caused enormous environmental damage to the ozone layer caused by chlorofluorocarbons. The plasticizers used for PVC are concerning because of their possible endocrine disrupting effects. This has led to political uncertainty and insecurity for companies working with PVC. The company HRD Carpets AB wishes to develop an alternative replacement material for PVC plastic carpets and looks preferably towards a bio-based solution. The purpose of this study is to find a suitable replacement material for PVC plastic carpets. The goal of this study is to provide a basis for an alternative replacement material and can be further developed in the form of further studies. The requirements specifications have been the starting point in this study to find a suitable replacement material. The mechanical properties of PVC, which is used in the company, have been identified and interpreted through a tensile test. These properties have been the elementary requirements combined with other requirements that appear in the requirements specification. This study examines alternative biomaterials and synthetic materials. With the help of the Cambridge Engineering Selector software, a selection of materials was found through a selection process. Then through interviews, publications, journals and literature, bio-based alternatives have been explored. The results showed that the synthetic plastic Polybutylene Terephthalate (PBT) together with color additives meet the basic requirements specification being investigated. The results also showed that the biomaterial Polylactic Acid (PLA) and Polybutene Succinate (PBS) meet the requirements and can function as alternative solutions. However, these materials have a short lifespan, increasing the durability of the material is a challenge with these biomaterials.

<p> The mechanism by which PVC particles remained stable in n-butylchloride was investigated.</p> <p> The PVC particles were made by aqueous emulsion polymerization with benzoyl peroxide initiator and polyvinyl alcohol surfactant. The particles were cleaned by ion exchange and their surface charge was found to be 0.068 ± 0.005 C/m^2. Dispersions of PVC in n-butylchloride were prepared by two methods. In the first, the particles were dried in an oven. The dried particles were redispersed in n-butylchloride via sonication. This produced a dispersion consisting of 0.26 kg/m^3 of PVC particles with an arithmetic volume average diameter of 317 nm and a standard deviation of 93 nm. The second method involved dialyzing the cleaned aqueous latex with methanol and then with n-butylchloride. The dialysis method was inferior to the sonication method. The dialysis method was time consuming, it produced a dispersion with large particle diameter, the dispersion was contaminated with water and methanol and surface species were removed by the methanol.</p> <p> The particles were found to be stabilized by an electrostatic mechanism. This was verified by observing that the particles migrated to the positive electrode when exposed to a potential difference of 1000 V. A surface potential of 0.203 V was calculated for the particles from mobility measurements and the Huckel equation.</p> <p> The charge separation that must occur to allow the particles to have the negative charge is hypothesized to be a result of organic molecules such as PVC-PVA oligomers that dissolve from the particles and form micelles. These molecules were readily soluble in methanol and only slightly soluble in n-butylchloride. As a result, when the dispersion was washed with methanol, the particles flocculated. The presence of these species in the dispersant was supported by evidence from ultra-violet, infra-red and nuclear magnetic resonance spectroscopy. The electronegative groups in the micelles provide a reasonably polar environment for hydrogen ions to exist. These hydrogen ions became the countercharge for the negatively charged particles.</p> / Thesis / Master of Engineering (MEngr)

No description available.

No description available.

The adverse effects of contaminated outdoor air have been recognized and subject to control for many years. More recently environmental engineers and health professionals have become cognizant of the hazards associated with contaminated indoor air. It is now understood that contaminated indoor air negatively impacts human health, worker productivity, and physical property. Volatile organic compounds (VOCs) are a common class of indoor air pollutants. Building materials such as treated wood, pressed-wood products, wallboard, sealants, adhesives, floor coverings, and paints can be sources of VOC emissions. The knowledge-base necessary to develop effective solutions to indoor air quality problems requires an understanding of the emissions behavior of indoor materials. Environmental chambers are often utilized to characterize indoor material as sources of VOC emissions to indoor air. Chamber studies, although expensive and time consuming, can be utilized to provide estimates of the rates at which a particular material emits VOCs under a specific set of environmental conditions. By fitting curves to emissions data obtained through chamber studies, VOC emissions models have been constructed. These models are frequently empirical and as a consequence, 1) apply only to the specific material and environmental conditions investigated, 2) provide little understanding of the source/sink characteristics of the material, and 3) provide little knowledge of the mass transfer processes governing emissions behavior. As a result, our understanding of the mechanisms that control VOC emissions from indoor materials remains rudimentary. Physically-based models that describe the emissions characteristics of building materials would greatly facilitate the process of improving indoor air quality. Evidence exists suggesting well-established fundamental mass transfer mechanisms govern emissions from indoor materials. Of the various mechanisms governing emissions behaviors, diffusion appears to be one of the most significant. The primary objective of this research was to demonstrate that the VOC emissions source behavior of a diffusion-controlled homogenous building material could be predicted using a mechanistic mathematical model. A commercial grade sheet vinyl flooring (VF) was selected for study because VF is present in many residential and commercial buildings, is relatively homogenous, and has been shown to emit hazardous organic chemicals. If successful, this research would demonstrate that the proposed strategy could be generalized to other VOC sources using appropriately constructed mathematical models. Satisfying the research objective required development of a physically-based model to predict gas-phase VOC concentrations resulting from exposure to a diffusion-controlled material. Key parameters for this model are the solid-phase diffusion coefficient, D; the solid/air partition coefficient, K; and the initial solid-phase VOC concentration, C0. D and K have been previously quantified for only a few indoor materials and methods for determining C0 are rudimentary. Therefore, this research project required development and execution of methods for quantifying D, K, and C0. D and K were quantified using a recording microbalance. C0 was evaluated using a new technique of cryogenic milling followed by fluidized bed desorption. The model was validated by exposing a VF sample in an environmental chamber and directly measuring gas-phase VOC concentrations resulting from mass transfer from the solid material. Further model validation was achieved by directly measuring the VOC concentration profiles after exposure in environmental chambers. Because the key model parameters were quantified independently of chamber studies, the model validation process provided a rigorous test of the validity of the mass transfer model in particular and of the source characterization strategy in general. The results of this research contribute to our understanding of the fundamental mechanisms that govern emissions of VOCs from vinyl flooring and provide a sound theoretical foundation for characterization of a wide range of other sources of indoor VOCs. This understanding could facilitate product reformulation strategies aimed at preventing or reducing indoor air contamination. Mass transfer models could also be utilized to develop standards for the environmental performance of indoor materials. The proposed approach will prove useful in conjunction with broader studies on sick building syndrome to identify sources that may have a critical impact on the health and comfort of building occupants. / Ph. D.