No description available.

No description available.

In this study, the viscoelastic and morphological characterization of molded foams was the main focus. A series of molded foams based on toluene diisocyanate (TDI) and glycerol initiated polyethylene-oxide-capped propylene-oxide was studied in terms of the structure property features. The results were in many instances compared to those obtained on conventional slabstock foams based on TDI and glycerol initiated propylene-oxide. These comparisons were made to delineate and clarify distinct differences between these two different and very important systems. It was found that high temperatures and humidities "plasticized" the viscoelastic behavior of molded foams to a greater extent than that of slabstock foams; the molded foams displayed higher load decay values in the viscoelastic measurements than slabstock foams. In an attempt to understand these dramatic differences, the two types of “cross-links" (covalent cross-links and urea based phase separated hard segment domains) were evaluated. It was discovered that the structure of the hard segment domains dictated the foam's behavior, especially at elevated temperatures and humidity. Furthermore, it was found that the hard segment domains in slabstock foams had a much higher level of short range ordering. This was confirmed by wide-angle x-ray scattering (WAXS) and fourier transform infrared (FTIR) which revealed that the conventional slabstock foams had much more organized hard segment domains. It is thus concluded that the dramatic differences between the mechanical properties of molded and slabstock foams are due to the lower and weaker ordering of the hard segments in molded systems making these physical "cross-links" more labile at higher temperatures and humidities. These morphological differences were shown to be due primarily to differences in the formulation components between the two studied systems. First, the ethylene-oxide capping used in the polyol of molded foams to increase the reactivity is known to also increase the compatibility between the hard and soft segments thus promoting some phase-mixing. Second, the addition of diethanolamine (DEOA) added in the molded foam formulation to decrease demold times by enhancing cross-linking clearly resulted in the prevention of the full development of the hard-segment domains. It was also found that the copolymer polyol particles (CPP), added to molded foams to increase load bearing capabilities, had a negative effect on the viscoelastic properties. The viscoelastic properties of the CPP containing foams were more time-dependent than those of the foams lacking these particles. As expected, the incorporation of these particles increased the initial load and decreased the initial strain over the foams lacking the particles suggesting that the initial stiffness of these materials was increased. However, over a period of time, the amount of this initial load that decayed was greater for the CPP containing foams and furthermore, at elevated conditions, the load decreased to levels below those of the CPP lacking foams. A series of slabstock foams was also studied to evaluate the effect of toluene diisocyanate (TDI) index on the physical properties, and morphology of the foams. Extraction experiments using dimethyl formamide (DMF) showed that increasing the index increased the level of covalent cross-linking with perhaps a maximum being reached at an index of 100. Viscoelastic measurements also supported the claim of increased crosslinking with TDI index. The initial load in load relaxation experiments systematically increased with increasing TDI while the percent decay in a three hour period decreased. Temperature and/or humidity "plasticized" the load relaxation behavior in all the foams studied indicating that the hard segment domain physical "cross-links" play a significant role in the properties of these materials. The morphology of the foams was also found to be influenced by the TDI index. Small angle x-ray scattering (SAXS), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) all provided evidence that an increase in the TDI index promoted phase mixing. FTIR and WAXS showed that the short range ordering within the hard segment domains displayed a maximum at an index of 100 and decreased as the index was increased. Finally, the influence of transient moisture conditions on the viscoelastic behavior was also investigated. In creep extractions, as the moisture conditions were cycled from low to high humidity while maintaining constant temperature, the compressive strain increased in subsequent steps where the strain levels under cyclic moisture conditions surpassed those observed at the highest constant relative humidity. This overall phenomenon of enhanced creep under cyclic moisture levels was attributed to water interacting with the hydrogen bonded structure within the foam. These hydrophillic interactions, principally promoted within the hard segment regions due to high hydrogen bonding, are disrupted causing slippage and increases in strain. As the foam is rapidly dried, regions of free volume are induced by the loss of water thus causing further increases in strain prior to the re-establishment of well ordered hydrogen bonding. / Ph. D.

Cavity balancing is the process of altering the flow front within a cavity through thickness and design changes such that the desired fill pattern is achieved. The 2 dimensional (2D) cavity-balancing algorithm, developed by Lam and Seow [1] can only handle 2D geometry. This represents a major drawback as most, if not all of the practical injected parts are not 2D parts. To overcome this difficulty, the present investigation has developed a 2.5 dimensional (2.5D) cavity balancing optimization routine implemented within a 2.5 D finite elements domain. The aim of the automated cavity balancing routine is to reduce product development time and to improve product quality. This will lower the level of prerequisite expert knowledge necessary for successful mold and part design. The automated cavity balancing routine has been developed using the concept of flow paths. The hill-climbing algorithm of Lam and Seow is utilized but modified for the generation of flow paths for 2.5D parts. The algorithm has been implemented in a computer program running as an external loop to the MOLDFLOW software. Case studies are provided to demonstrate the efficiency of this routine. / Singapore-MIT Alliance (SMA)

No description available.

Se as margens para ganhos financeiros são estreitas e o lucro está atrelado à produtividade, como ocorre nas indústrias de injeção de termoplásticos, cada centavo deve ser considerado. Cada perda no processo deve ser minimizada seja com redução em tempo de ciclo, redução em tempo de máquina parada, estudos de setup, automatização ou reciclagem, não somente de produtos não conformes e canais e de injeção, prática comum nas empresas transformadoras, mas também, das borras plásticas geradas no processo de purga de máquinas injetoras. O presente trabalho propõe a realização de um estudo acerca da viabilidade técnica para a reutilização e reprocessamento da matéria-prima obtida a partir das borras plásticas injetadas, um resíduo industrial, evitando sua deposição no meio ambiente ou venda como sucata, visando um fim mais nobre para esse resíduo tão comum nas empresas de transformação de termoplásticas por injeção. O envelhecimento das amostras por exposição natural e a comparação da performance entre amostras expostas e não expostas possibilitou um estudo comparativo de diversas propriedades e do comportamento do PEAD oriundo de borras plásticas injetadas. A fim de viabilizar a reciclagem, uma metodologia que incluiu procedimentos de coleta, separação, classificação, corte, moagem e formulação de misturas com diferentes frações de moído de borra de PEAD e PEAD virgem é apresentada. Com a realização de ensaios físicos, térmicos, mecânicos, reológicos obteve-se meios para analisar e avaliar as propriedades do polietileno de alta densidade (PEAD) proveniente de borras plásticas injetadas. Ressalta-se que, as condições de exposição ao intemperismo natural ao qual as amostras foram submetidas nesse estudo, são consideradas agressivas, visto que a radiação ultravioleta (UV) chegou ao índice extremo de acordo com a classificação utilizada pela OMS. Por fim, concluiu-se que para aplicações em bens duráveis, que serão expostos ao intemperismo natural, o simples fracionamento entre material reciclado, oriundo de borras plásticas injetadas e PEAD virgem não se mostra eficiente, pois há perda de propriedades mecânicas, principalmente no alongamento na ruptura. A aditivação das formulações é uma opção para obtenção de melhores resultados embora envolva custos adicionais. / If the margins are narrow for financial winnings and the profit is related to productivity, as occurs in thermoplastic injection industries, every penny should be considered. Each loss in the process should be minimized such as a reduction in cycle time, reduction in downtime, set up studies, automation or recycling not only of off-specification products and branch injection, common practice in manufacturing companies, but also, plastic sludge generated in the injection machines purge process. This paper proposes the achievement of a study about the technical viability for reuse and reprocessing of raw materials obtained from the injected plastic sludge, a industrial waste, preventing their deposition in the environment or their sale as scrap, seeking a nobler end for that residue so common in thermoplastic processing industries by injection. The aging of samples by natural exposure and the comparison of the performance between exposed and unexposed samples made possible a comparative study of various properties and the collection of information about the properties and behavior of reprocessed HDPE from injected plastic sludges. In order to facilitate recycling, a methodology that included procedures for collecting, separating, sorting, cutting, grinding and formulation of mixtures with different ground fractions of HDPE grounds and virgin HDPE is presented. Com a realização de ensaios físicos, térmicos, mecânicos, reológicos obteve-se meios para analisar e avaliar as propriedades do polietileno de alta densidade (PEAD) proveniente de borras plásticas injetadas. With the realization of physical tests, thermal, mechanical, rheological was obtained ways to analyze and evaluate the high-density polyethylene properties (HDPE) plastic injection-molded from sludges. It is noteworthy that, the conditions of exposure to natural weathering which the samples were submitted in this study are considered aggressive, once the ultraviolet (UV) index was considerated extreme according to the classification used by WHO. Finally, it was concluded that for applications in durable products, which will be exposed to natural weathering, the simple fractionation of recycled material coming from injected plastic sludge and virgin HDPE is inefficient because there is loss of mechanical properties, especially in the stretch at break. The additivation of formulations is an option for better results even though it involves additional costs.

Se as margens para ganhos financeiros são estreitas e o lucro está atrelado à produtividade, como ocorre nas indústrias de injeção de termoplásticos, cada centavo deve ser considerado. Cada perda no processo deve ser minimizada seja com redução em tempo de ciclo, redução em tempo de máquina parada, estudos de setup, automatização ou reciclagem, não somente de produtos não conformes e canais e de injeção, prática comum nas empresas transformadoras, mas também, das borras plásticas geradas no processo de purga de máquinas injetoras. O presente trabalho propõe a realização de um estudo acerca da viabilidade técnica para a reutilização e reprocessamento da matéria-prima obtida a partir das borras plásticas injetadas, um resíduo industrial, evitando sua deposição no meio ambiente ou venda como sucata, visando um fim mais nobre para esse resíduo tão comum nas empresas de transformação de termoplásticas por injeção. O envelhecimento das amostras por exposição natural e a comparação da performance entre amostras expostas e não expostas possibilitou um estudo comparativo de diversas propriedades e do comportamento do PEAD oriundo de borras plásticas injetadas. A fim de viabilizar a reciclagem, uma metodologia que incluiu procedimentos de coleta, separação, classificação, corte, moagem e formulação de misturas com diferentes frações de moído de borra de PEAD e PEAD virgem é apresentada. Com a realização de ensaios físicos, térmicos, mecânicos, reológicos obteve-se meios para analisar e avaliar as propriedades do polietileno de alta densidade (PEAD) proveniente de borras plásticas injetadas. Ressalta-se que, as condições de exposição ao intemperismo natural ao qual as amostras foram submetidas nesse estudo, são consideradas agressivas, visto que a radiação ultravioleta (UV) chegou ao índice extremo de acordo com a classificação utilizada pela OMS. Por fim, concluiu-se que para aplicações em bens duráveis, que serão expostos ao intemperismo natural, o simples fracionamento entre material reciclado, oriundo de borras plásticas injetadas e PEAD virgem não se mostra eficiente, pois há perda de propriedades mecânicas, principalmente no alongamento na ruptura. A aditivação das formulações é uma opção para obtenção de melhores resultados embora envolva custos adicionais. / If the margins are narrow for financial winnings and the profit is related to productivity, as occurs in thermoplastic injection industries, every penny should be considered. Each loss in the process should be minimized such as a reduction in cycle time, reduction in downtime, set up studies, automation or recycling not only of off-specification products and branch injection, common practice in manufacturing companies, but also, plastic sludge generated in the injection machines purge process. This paper proposes the achievement of a study about the technical viability for reuse and reprocessing of raw materials obtained from the injected plastic sludge, a industrial waste, preventing their deposition in the environment or their sale as scrap, seeking a nobler end for that residue so common in thermoplastic processing industries by injection. The aging of samples by natural exposure and the comparison of the performance between exposed and unexposed samples made possible a comparative study of various properties and the collection of information about the properties and behavior of reprocessed HDPE from injected plastic sludges. In order to facilitate recycling, a methodology that included procedures for collecting, separating, sorting, cutting, grinding and formulation of mixtures with different ground fractions of HDPE grounds and virgin HDPE is presented. Com a realização de ensaios físicos, térmicos, mecânicos, reológicos obteve-se meios para analisar e avaliar as propriedades do polietileno de alta densidade (PEAD) proveniente de borras plásticas injetadas. With the realization of physical tests, thermal, mechanical, rheological was obtained ways to analyze and evaluate the high-density polyethylene properties (HDPE) plastic injection-molded from sludges. It is noteworthy that, the conditions of exposure to natural weathering which the samples were submitted in this study are considered aggressive, once the ultraviolet (UV) index was considerated extreme according to the classification used by WHO. Finally, it was concluded that for applications in durable products, which will be exposed to natural weathering, the simple fractionation of recycled material coming from injected plastic sludge and virgin HDPE is inefficient because there is loss of mechanical properties, especially in the stretch at break. The additivation of formulations is an option for better results even though it involves additional costs.

Se as margens para ganhos financeiros são estreitas e o lucro está atrelado à produtividade, como ocorre nas indústrias de injeção de termoplásticos, cada centavo deve ser considerado. Cada perda no processo deve ser minimizada seja com redução em tempo de ciclo, redução em tempo de máquina parada, estudos de setup, automatização ou reciclagem, não somente de produtos não conformes e canais e de injeção, prática comum nas empresas transformadoras, mas também, das borras plásticas geradas no processo de purga de máquinas injetoras. O presente trabalho propõe a realização de um estudo acerca da viabilidade técnica para a reutilização e reprocessamento da matéria-prima obtida a partir das borras plásticas injetadas, um resíduo industrial, evitando sua deposição no meio ambiente ou venda como sucata, visando um fim mais nobre para esse resíduo tão comum nas empresas de transformação de termoplásticas por injeção. O envelhecimento das amostras por exposição natural e a comparação da performance entre amostras expostas e não expostas possibilitou um estudo comparativo de diversas propriedades e do comportamento do PEAD oriundo de borras plásticas injetadas. A fim de viabilizar a reciclagem, uma metodologia que incluiu procedimentos de coleta, separação, classificação, corte, moagem e formulação de misturas com diferentes frações de moído de borra de PEAD e PEAD virgem é apresentada. Com a realização de ensaios físicos, térmicos, mecânicos, reológicos obteve-se meios para analisar e avaliar as propriedades do polietileno de alta densidade (PEAD) proveniente de borras plásticas injetadas. Ressalta-se que, as condições de exposição ao intemperismo natural ao qual as amostras foram submetidas nesse estudo, são consideradas agressivas, visto que a radiação ultravioleta (UV) chegou ao índice extremo de acordo com a classificação utilizada pela OMS. Por fim, concluiu-se que para aplicações em bens duráveis, que serão expostos ao intemperismo natural, o simples fracionamento entre material reciclado, oriundo de borras plásticas injetadas e PEAD virgem não se mostra eficiente, pois há perda de propriedades mecânicas, principalmente no alongamento na ruptura. A aditivação das formulações é uma opção para obtenção de melhores resultados embora envolva custos adicionais. / If the margins are narrow for financial winnings and the profit is related to productivity, as occurs in thermoplastic injection industries, every penny should be considered. Each loss in the process should be minimized such as a reduction in cycle time, reduction in downtime, set up studies, automation or recycling not only of off-specification products and branch injection, common practice in manufacturing companies, but also, plastic sludge generated in the injection machines purge process. This paper proposes the achievement of a study about the technical viability for reuse and reprocessing of raw materials obtained from the injected plastic sludge, a industrial waste, preventing their deposition in the environment or their sale as scrap, seeking a nobler end for that residue so common in thermoplastic processing industries by injection. The aging of samples by natural exposure and the comparison of the performance between exposed and unexposed samples made possible a comparative study of various properties and the collection of information about the properties and behavior of reprocessed HDPE from injected plastic sludges. In order to facilitate recycling, a methodology that included procedures for collecting, separating, sorting, cutting, grinding and formulation of mixtures with different ground fractions of HDPE grounds and virgin HDPE is presented. Com a realização de ensaios físicos, térmicos, mecânicos, reológicos obteve-se meios para analisar e avaliar as propriedades do polietileno de alta densidade (PEAD) proveniente de borras plásticas injetadas. With the realization of physical tests, thermal, mechanical, rheological was obtained ways to analyze and evaluate the high-density polyethylene properties (HDPE) plastic injection-molded from sludges. It is noteworthy that, the conditions of exposure to natural weathering which the samples were submitted in this study are considered aggressive, once the ultraviolet (UV) index was considerated extreme according to the classification used by WHO. Finally, it was concluded that for applications in durable products, which will be exposed to natural weathering, the simple fractionation of recycled material coming from injected plastic sludge and virgin HDPE is inefficient because there is loss of mechanical properties, especially in the stretch at break. The additivation of formulations is an option for better results even though it involves additional costs.

Orientador: Marco-Aurelio De Paoli / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-07T18:50:45Z (GMT). No. of bitstreams: 1 Maia_DenisonRicardoJustino_D.pdf: 7384890 bytes, checksum: efeedfba27b5af359387e70f46fd71c7 (MD5) Previous issue date: 2006 / Resumo: No presente trabalho foi estudado uma alternativa para atenuar a degradação e o embranquecimento de peças injetadas de poli(propileno-co-etileno) contendo TiO2. O pigmento branco TiO2 (rutilo e anatase) apresenta efeito catalítico na degradação fotoxidativa do polímero, em um processo iniciado pela reação de um elétron fotoexcitado na banda de condução do TiO2 com oxigênio atmosférico. Durante longos períodos de exposição ambiental das peças observa-se que a tensão gerada por flexão não tem efeito detectável na degradação, tendo-se atribuído o fenômeno a processos de relaxação das cadeias poliméricas. Com intuito de minimizar os efeitos catalíticos do TiO2 foi utilizado o pigmento preto negro de fumo condutor (NFcd) em substituição ao negro de fumo comum (NFcm), sendo observado menor degradabilidade para estas amostras. O efeito não foi verificado para amostras que não continham TiO2, e assim mostrou-se que o processo está relacionado à interação do NFcd com o TiO2. Propõe-se que as características condutoras do pigmento preto estão relacionadas à desativação do elétron fotoexcitado do catalisador TiO2. Em testes com nove estabilizantes comerciais foi selecionado o sistema estabilizante NDS Anox¿ como o mais efetivo na estabilização da formulação, combinando alta estabilidade e maior homogeneidade das características degradativas das amostras. Em adição, não foi verificada interação sinérgica ou antagônica entre o estabilizante NDS Anox¿ e o NFcd, mostrando que a alta eficiência do estabilizante constitui-se na variável mais importante na estabilização do material. Também apresentamos nesse trabalho uma alternativa de aplicação para a técnica quimiométrica mapas auto-organizáveis (SOM), utilizada no tratamento e classificação de espectros de reflectância FT -IR, se mostrando uma ferramenta útil na caracterização comparativa da degradação das amostras poliméricas. / Abstract: In this work we studied an alternative to minimize degradation and whitening of injected parts made of TiO2 containing poly(propylene-co-ethylene). The catalytic effect of the white pigment TiO2 (anatase and rutile) in the polymer photooxidation has been assigned to the reaction of an excited electron in the conduction band of TiO2 with atmospheric O2. For long periods of ambient exposition it was observed that tension generated by flexion does not affect degradation, and it was assigned to polymeric chain relaxation processes. To minimize catalytic action of TiO2 we used the black pigment conducting carbon black (CCB) in substitution to the non conducting grade (CB), and it has been verified less degradation in these samples. The effect was not observed for samples without TiO2, hence the process is related to the interaction between CCB and TiO2. We propose that the improvement of stability is associated to deactivation of the excited electron in the conduction band of TiO2. Tests of nine commercial stabilizer mixtures have selected NDB Anox¿ as the most effective in the formulation stabilization, combining high stability and greater homogeneity of samples degradation characteristics. In addition synergistic or antagonistic interaction was not observed between NDB Anox¿ and CCB, showing that the high stability provided by the stabilizer system is the major variable in the material stabilization. We also present an alternative application for self-organizing maps (SOM), used in this work for FTIR reflectance spectra treatment and classification, providing an useful tool in the characterization of comparative degradation of polymeric samples. / Doutorado / Quimica Inorganica / Doutor em Ciências

Företaget AB Strängbetong har på senare tid noterat ett ökat antal ingjutna lyft i tillverkningen av håldäckselement vilket skapar merarbeten. För att kunna vara konkurrenskraftiga på marknaden krävs en billig och effektiv produkt som är enkel att tillverka. Det ökade antalet ingjutna lyft höjer priset på produkten samtidigt som tillverkningen kompliceras. Syftet med denna rapport ligger därför i att undersöka orsaken till den ökade mängden ingjutna lyft i håldäckselementen, men även vilka förbättringsmöjligheter som finns. För att ge svar på den ställda problemformuleringen har intervjuer genomförts med anställda på företaget AB Strängbetong som är en av de ledande stomentreprenörerna på den svenska marknaden. Metoden har kompletterats med en litteraturgenomgång av företagets standarder och arbetsmiljöverkets föreskrifter.Ökningen beror till stor del på ett ökat säkerhetsfokus kombinerat med mer komplexa konstruktioner. Anledningen till att håldäckselement i första hand ska förses med ingjutna lyft är då ingreppen i plattan blivit så omfattande att lyft med ordinarie lyftutrustning ej är möjliga, men även på grund av avsaknaden av materiella resurser vid mindre projekt. Det finns emellertid meningsskiljaktigheter angående ingjutna lyft där vissa av de anställda, med anknytning till montage, inte ser det ökade antalet som ett problem utan snarare som en vinst på grund av säkrare och effektivare montage.Slutsatsen är att inte se ingjutna lyft som den primära lösningen. I stället bör det ses över om det konstruktionsmässigt går att undvika ingrepp i de kritiska delarna av håldäckselementen. I kombination med fler resurser till mindre byggen samt lösningar i kringliggande konstruktionsdelar kan både tids- och kostnadsbesparingar göras. En effektivisering skulle i sin helhet troligen även minska klimatpåverkan. / The company AB Strängbetong has recently noted an increased number of molded lifts in the manufacture of hollow-core slabs, which generates additional work. To be market competitive requires a cheap and efficient product that is easy to manufacture. The increased number of molded lifts makes the product more expensive at the same time as the production becomes more complicated. The purpose of this report is therefore to investigate the cause of the increased number of molded lifts in the hollow-core slabs, and suggest how the process can be improved. To provide answers to the posed problem formulation, interviews were conducted with employees at the company AB Strängbetong, which is one of the leading frame contractors on the Swedish market. The method has been supplemented with a literature review of the company's standards and the Swedish Work Environment Authority's regulations.The increase is largely due to an increased safety focus combined with more complex constructions. The reason why hollow-core slabs should primarily be provided with molded lifts is not only for when the interventions in the element have become so extensive that lifting with ordinary lifting equipment is not possible, but also due to a lack of material resources for smaller projects. However, there are differences of opinion regarding molded lifts where some of the employees, who work with assembly, do not see the increased number of as a problem but rather as a gain due to safer and more efficient assembly procedures.The conclusion is to not see molded lifts as the primary solution. It should rather be considered whether it is structurally possible to avoid interference with the critical parts of the hollow-core slabs. In combination with more resources for smaller constructions as well as solutions in surrounding construction parts, both time and cost savings can be made. An increase in efficiency as a whole would probably also reduce the climate impact of the company.