A reciclagem de diversos tipos de materiais tem adquirido importância nos últimos anos. Problemas ambientais graves como o acúmulo de rejeitos e a poluição atmosférica, causados pelo crescente consumo de materiais poliméricos, incentivam estudos para o desenvolvimento de diferentes formas de reaproveitamento. Entretanto, a reciclagem de polímeros elastômeros tem demonstrado grande complexidade, pois o material depois de vulcanizado não pode ser remoldado pelo simples aquecimento. A desvulcanização por microondas é uma técnica promissora para contornar este problema, uma vez que possibilita restituir a capacidade de moldagem dos elastômeros. Neste trabalho foi feito um estudo sobre a desvulcanização por micro-ondas em processo contínuo e em batelada do elastômero estireno-butadieno (SBR) com diferentes quantidades de negro de fumo e em diferentes condições de processamento, de modo a avaliar os processos de desvulcanização e esclarecer melhor os fenômenos e reações químicas envolvidas. A eficiência dos diferentes sistemas de desvulcanização adotados foi avaliada por meio de análises termogravimétricas (TG), dinâmico-mecânicas (DMA), calorimetria exploratória diferencial (DSC), espectroscopia no infravermelho (FTIR), espectrometria de ressonância magnética nuclear (RMN), densidade de ligação cruzada e teor de gel. A desvulcanização foi mais efetiva no elastômero SBR com maiores teores de negro de fumo, empregando o sistema de desvulcanização em batelada com uma única fonte de radiação, enquanto que a desvulcanização contínua não apresentou resultados relevantes para o sistema adotado. O material desvulcanizado demonstrou mudanças químicas e físicas consideráveis na sua estrutura. Assim, a reciclagem de elastômeros utilizando a energia das micro-ondas torna-se possível e provoca mudanças estruturais no material para borracha com altos teores de negro de fumo utilizando o sistema batelada. / The recycling of several materials has acquired importance in the last few years. Serious environmental problems as the increase in waste material and air pollution, caused by the growing consumption of polymeric material, stimulate works to development of distinct ways of reclamations. However, the recycling of elastomers has demonstrated more complexity than other polymeric materials because, after vulcanized, the material can not be remolded by simple heating. The microwave devulcanization is a promissory technique to solve this problem, in as it makes it possible to replace the remold capacity of elastomers. In this work it was studied the devulcanization by microwave in continuous and batch processes of styrene-butadiene rubber (SBR) with different amount of carbon black (CB) and in different process conditions, to evaluate the devulcanization process and to clarify the involved phenomena and chemical. The efficiency of distinct devulcanization systems was evaluated through thermogravimetric analyses (TG), dynamic-mechanical analysis (DMA), differential scattering calorimetric (DSC), Fourier transformed infrared (FTIR), nuclear magnetic resonance (NMR), crosslink density and gel content analysis. The devulcanization was more effective in SBR elastomer with higher amount of carbon black, used the batch systems devulcanization with a single source of radiation, whereas the continuous devulcanization did not show relevant results to the adopted system. The devulcanized material exhibited considerable chemical and physical alteration in its structure. Thus, the elastomers recycling using the microwave energy is possible and generates structural modification in the material for rubber with high amount of carbon black in batch system.

A reciclagem de diversos tipos de materiais tem adquirido importância nos últimos anos. Problemas ambientais graves como o acúmulo de rejeitos e a poluição atmosférica, causados pelo crescente consumo de materiais poliméricos, incentivam estudos para o desenvolvimento de diferentes formas de reaproveitamento. Entretanto, a reciclagem de polímeros elastômeros tem demonstrado grande complexidade, pois o material depois de vulcanizado não pode ser remoldado pelo simples aquecimento. A desvulcanização por microondas é uma técnica promissora para contornar este problema, uma vez que possibilita restituir a capacidade de moldagem dos elastômeros. Neste trabalho foi feito um estudo sobre a desvulcanização por micro-ondas em processo contínuo e em batelada do elastômero estireno-butadieno (SBR) com diferentes quantidades de negro de fumo e em diferentes condições de processamento, de modo a avaliar os processos de desvulcanização e esclarecer melhor os fenômenos e reações químicas envolvidas. A eficiência dos diferentes sistemas de desvulcanização adotados foi avaliada por meio de análises termogravimétricas (TG), dinâmico-mecânicas (DMA), calorimetria exploratória diferencial (DSC), espectroscopia no infravermelho (FTIR), espectrometria de ressonância magnética nuclear (RMN), densidade de ligação cruzada e teor de gel. A desvulcanização foi mais efetiva no elastômero SBR com maiores teores de negro de fumo, empregando o sistema de desvulcanização em batelada com uma única fonte de radiação, enquanto que a desvulcanização contínua não apresentou resultados relevantes para o sistema adotado. O material desvulcanizado demonstrou mudanças químicas e físicas consideráveis na sua estrutura. Assim, a reciclagem de elastômeros utilizando a energia das micro-ondas torna-se possível e provoca mudanças estruturais no material para borracha com altos teores de negro de fumo utilizando o sistema batelada. / The recycling of several materials has acquired importance in the last few years. Serious environmental problems as the increase in waste material and air pollution, caused by the growing consumption of polymeric material, stimulate works to development of distinct ways of reclamations. However, the recycling of elastomers has demonstrated more complexity than other polymeric materials because, after vulcanized, the material can not be remolded by simple heating. The microwave devulcanization is a promissory technique to solve this problem, in as it makes it possible to replace the remold capacity of elastomers. In this work it was studied the devulcanization by microwave in continuous and batch processes of styrene-butadiene rubber (SBR) with different amount of carbon black (CB) and in different process conditions, to evaluate the devulcanization process and to clarify the involved phenomena and chemical. The efficiency of distinct devulcanization systems was evaluated through thermogravimetric analyses (TG), dynamic-mechanical analysis (DMA), differential scattering calorimetric (DSC), Fourier transformed infrared (FTIR), nuclear magnetic resonance (NMR), crosslink density and gel content analysis. The devulcanization was more effective in SBR elastomer with higher amount of carbon black, used the batch systems devulcanization with a single source of radiation, whereas the continuous devulcanization did not show relevant results to the adopted system. The devulcanized material exhibited considerable chemical and physical alteration in its structure. Thus, the elastomers recycling using the microwave energy is possible and generates structural modification in the material for rubber with high amount of carbon black in batch system.

One of the current problems faced by mankind is the problem of safe disposal of waste rubber. Statistics show that the number of waste tires is continuously increasing at a very rapid rate. Since rubber materials do not decompose easily (due to their crosslinked structure), they end up being a serious ???environmental problem???. An intuitive solution to prevent the accumulation of the scrap tires is to continuously reuse them. A new patented reclamation method was discovered in our laboratory, which makes use of a twin screw extruder (TSE) in order to produce reclaimed rubber (referred as devulcanized rubber (DR) from here on) of very high quality. Also, this method has proven to be more economical than other commercial reclaiming methods. Products made solely from a reclaimed material face challenges from those made by virgin materials because of relatively poor properties. However, the striking advantage of using reclaimed rubbers is the cost reduction. Hence, it is important to work on establishing methods by which these reclaimed rubbers could be efficiently used and incorporated into present day products. The deterioration of properties could be minimized by blending them with varying amounts of other materials. A possibility in this direction is manufacturing of thermoplastic vulcanizates (TPVs) using reclaimed rubber and general purpose thermoplastics. In accordance with this idea, the focus of this research is to prepare DR and polypropylene (PP) based TPVs. DR is unique as the rubber itself consists of two phases- one phase consisting of uncrosslinked (including devulcanized rubber molecules), and the other phase consisting of crosslinked (un-devulcanized) rubber. These un-devulcanized crumbs act as stress concentrators because they do not break-up easily, and lead to poor physical properties. Hence, this project tries to find out ways to increase the interfacial adhesion between the rubber and PP by using reactive and non-reactive techniques. Preliminary experiments were carried out in a batch mixer to compare DR and rubber crumb (CR). DR based TPVs showed better properties than CR based TPVs, however, the properties were not useful for commercial applications. Sulphur based dynamic vulcanization was studied in a batch mixer and found to be not effective in improving the properties of DR based blends. On the other hand, DCP/ sulphur based curing system was found to show significant improvement in properties. Therefore, DCP/sulphur based curing package was studied in detail on the blends consisting of DR and PP. The optimum ratio of DCP/sulphur was found to vary depending on the ratio of DR/PP. A hypothesis regarding the mechanism of DCP/sulphur curing has been proposed, which seem to correlate well with the experimental results observed. Additionally, it was determined that DR prepared from tire rubber (DRT) performed better than DR prepared from waste EPDM (DRE) for the curing system used. Accordingly, experiments on a TSE were carried out using DRT and a combination of compatibilizing resins and curatives. This combination showed a drastic improvement in blends properties and once again the optimum ratio of compatibilizing resins seemed to depend on the ratio of DRT/PP. As a result of the work, successful strategies based on reactive compatibilization techniques were developed in order to prepare useful TPVs having up to 70% DR. A series of compatibilization techniques has been evaluated using design of experiments and various characterization techniques such as mechanical tests, scanning electron microscopy, thermal analysis and crosslink density measurements. This led to the development of a formulation, which could improve the blend properties significantly. A tensile strength of around 10 MPa and an elongation-at-break of 150-180 % could be achieved for devulcanized rubber (70%) based TPVs, which has broadened the scope for its commercial applications. In addition to that, the process was established on a TSE that has enabled a continuous and steady production of these TPVs with reasonable throughputs.

abstract: It is common to use crumb rubber as modifier in bitumen. Good performance of crumb rubber in bitumen has been reported in terms of improving characteristics like higher skid resistance, reducing noise, higher rutting resistance and longevity. However, due to the vulcanization, the polymeric crosslinked structure of crumb rubber suffers from inadequate dispersion and incompatibility in bitumen where storage stability becomes an issue. To solve this problem, partial surface devulcanization of the rubber via chemical and microbial surface activation was examined in this study showing both method can be effective to enhance rubber-bitumen interactions and subsequently storage stability of the rubberized bitumen. To ensure proper surface activation, it is important to thoroughly understand chemo-mechanics of bitumen containing rubber particles as well as underlying interaction mechanism at the molecular level. Therefore, this study integrates a multi-scale approach using density functional theory based computational modeling and laboratory experiments to provide an in-depth understanding of the mechanisms of interaction between surface activated rubber and bitumen. To do so, efficacy of various bio-modifiers was examined and compared it terms of both surface activation capability and durability of resulting rubberized bitumen. It was found that biomodifiers with various compositions can have either synergistic or antagonistic effect onchemo-mechanics of rubberized bitumen. The study was further extended to study the interplay of Polyphosphoric Acid (PPA) and these biomodified rubberized bitumens showing not all modifiers have high synergy with PPA in bitumens. Finally, durability of rubberized bitumen was studied in terms of its resistance to Ultraviolet (UV) aging. It was shown that there is a strong relation between composition of biomodified rubberized bitumen and its resistance to UV-aging. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2020

No description available.

Made available in DSpace on 2017-07-21T20:42:34Z (GMT). No. of bitstreams: 1 Armando Madalosso Vieira Filho.pdf: 12599724 bytes, checksum: 65d627ecd808a90acce0c965752d8655 (MD5) Previous issue date: 2009-09-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Finding new ways and techniques of recycling has been one of the main paths searched by investigators to solve the problem of the garbage. For this study were chosen two of the polymers with large volumes of post-consumer material: LDPE and rubber tire. Several studies have been made to incorporate rubber tire in polymers by following different paths one of them is the devulcanization of rubber tire by microwave. The focus of this study was process and characterize blends of virgin and / or recycled LDPE with ground tire rubber. Both formulations, virgin and recycled LDPE, were made with percentage by weight of 0, 5, 10, 20 and 40 of rubber in and with percentage by weight of 0 and 10 in the blends of 50% virgin / 50% recycled LDPE. The formulations were processed into a of single screw extruder, granulated, injected and treated with microwave “in situ”. Tests were made for size distribution of the rubber, tensile, bending, optical and scanning electron microscopy, DSC and infrared spectroscopy. As results obtained were: a rubber tire can be used as an additive for staining, mechanical properties similar to almost all formulations was obtained with up to 10% of tire rubber. The amount of rubber incorporated and composition (recycled or virgin) influence the mechanical and thermal properties of some blends. The treatment with microwaves "in situ" presented influence on the mechanical and thermal properties in the formulations tested, presenting differential properties, such as increased maximum stress in some formulations, demonstrating that the study of the treatment is technologically interesting. / Encontrar novos meios e técnicas de reciclagem têm sido um dos grandes caminhos buscados por pesquisadores para resolver o problema do lixo. Para este estudo foram escolhidos dois dos polímeros com grandes volumes de material pós-consumo: PEBD e borracha de pneu. Várias pesquisas têm sido feitas no sentido de incorporar borracha de pneu em polímeros seguindo diversos caminhos e dentre eles está a desvulcanização da borracha por microondas. O objetivo deste trabalho foi processar e caracterizar misturas de PEBD virgem e/ou recicladas incorporadas com pó de borracha de pneu. Foram feitas formulações com teores de 0, 5, 10, 20 e 40% em peso de borracha no PEBD virgem e reciclado, e 0 e 10% em blendas de PEBD/ PEBD reciclado (50/50). As formulações foram processadas em extrusora de rosca simples, injetadas e tratadas com microondas “in situ”. Foram feitos ensaios de distribuição granulométrica da borracha, tração, flexão, microscopia, DSC e FTIR. Observou-se: que a borracha de pneu pode servir como aditivo para fins de coloração; propriedades mecânicas similares com até 10% de borracha para quase todas as formulações; que a quantidade de borracha incorporada e o tipo de matriz influenciam as propriedades mecânicas e térmicas. O tratamento “in situ” com microondas apresentou influência nas propriedades mecânicas e térmicas nas formulações ensaiadas apresentando propriedades diferenciadas, como aumento da tensão máxima em algumas formulações, demonstrando que o estudo do tratamento é interessante tecnologicamente.

Submitted by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T13:47:40Z No. of bitstreams: 1 DissRB.pdf: 6420019 bytes, checksum: 9a9303246e3fd99e5635cc0d40d684d5 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T13:47:48Z (GMT) No. of bitstreams: 1 DissRB.pdf: 6420019 bytes, checksum: 9a9303246e3fd99e5635cc0d40d684d5 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T13:47:53Z (GMT) No. of bitstreams: 1 DissRB.pdf: 6420019 bytes, checksum: 9a9303246e3fd99e5635cc0d40d684d5 (MD5) / Made available in DSpace on 2017-08-23T13:48:00Z (GMT). No. of bitstreams: 1 DissRB.pdf: 6420019 bytes, checksum: 9a9303246e3fd99e5635cc0d40d684d5 (MD5) Previous issue date: 2017-03-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The present study investigated the utilization efficiency of an intermeshing co-rotating twin-screw extruder (ICTSE) in the devulcanization of natural rubber compounds (NR), evaluating the physical, chemical and mechanical characteristics of these materials in each project step. Three accelerated compounds with different sulfur concentrations were submitted to torque rheometry and vulcanized according these results aiming the achievement of elastomers with different crosslinks densities. The influences on the characteristics of the devulcanized material caused by the variation of the extruder barrel temperature, screw rotation, thermoplastics addition and material stiffness were evaluated. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), soluble fraction extraction and crosslink density were performed, evaluating the devulcanized compound. Horikx's theory was also used as an indicator of selective crosslink cleavage, defining the compounds to be revulcanized for comparison with the virgin pure material. The revulcanization was carried out with the mixture of the devulcanized compound with the pure, in the proportions of 30/70 w/w, respectively, and in the devulcanized compound singularly, with addition of complementary vulcanization system in both cases. The mechanical, dynamic-mechanical and crosslink density properties of the revulcanized compounds were characterized and evaluated in relation to the properties of the pure compounds. The increase in the concentration of uncrosslinked BN chains and the concentration of sulfur compounds in the extruded samples was observed by thermal tests and spectrocopy, together with the verification of a high level of devulcanization percentage, according to Flory-Rehner, evidencing the regeneration of the natural rubber existent. Also, satisfactory mechanical properties were found in the revulcanized compounds, especially when using auxiliary thermoplastics, revealing the great potential of ERDCI processing for the reuse of discarded BN compounds. / O presente estudo avaliou a eficiência de utilização de uma extrusora com rosca dupla co-rotacional e interpenetrante (ERDCI) na desvulcanização de compostos de borracha natural (BN), avaliando as características físicas, químicas e mecânicas destes materiais em cada fase do projeto. Três compostos acelerados com diferentes concentrações de enxofre foram submetidos a reometria de torque, e vulcanizados de acordo com a curva reométrica, para obtenção de elastômeros com diferentes densidades de ligações cruzadas. Foram avaliadas as influências nas características do material desvulcanizado, causadas pela variação da temperatura do barril da extrusora, velocidade de rotação das roscas, adição de termoplásticos e módulo elástico do material. Análises de termogravimetria (TGA), calorimetria exploratória diferencial (DSC), espectroscopia no infravermelho (FTIR), fração solúvel (FS) e densidade de ligações cruzadas foram realizadas, avaliandose o composto desvulcanizado. A teoria de Horikx também foi utilizada como indicativa da seletividade de ruptura de ligações cruzadas, definindo os compostos a serem revulcanizados para comparação com o material virgem. A revulcanização foi realizada com a mistura de 30 %(m/m) do composto desvulcanizado e 70 %(m/m) do puro, e também com 100 % do composto desvulcanizado, e adição de sistema de vulcanização complementar. Caracterizou-se os compostos revulcanizados quanto às suas propriedades mecânicas, dinâmico-mecânicas e densidade de ligações cruzadas. Através dos ensaios TGA, DSC, FTIR e a verificação de alto nível de percentual de desvulcanização pela teoria de Flory- Rehner, foi observado o aumento da concentração de cadeias de BN não reticuladas e da concentração de compostos de enxofre nas amostras extrudadas, evidenciando a regeneração da BN presente nos compostos. Também foram encontradas propriedades mecânicas satisfatórias nos compostos revulcanizados, principalmente quando utilizados termoplásticos auxiliares, revelando o grande potencial do processamento por ERDCI para a reutilização de compostos de BN descartados.

La vulcanització per microones és un procés madur i no hi ha dubte sobre la seva eficiència per produir articles de cautxú d'alta qualitat. Les microones són conegudes no només per la seva capacitat d'accelerar els processos i augmentar la eficiència de la transferència energètica, sinó que també són capaces en certs casos de canviar els camins de reacció. Hi ha evidències, basades en canvis en propietats físiques al comparar productes vulcanitzats amb el mètode convencional i amb microones, que indiquen que alguns canvis poden succeir al treballar amb diferents fonts d'escalfament. No obstant això, hi ha una falta d'informació sobre els efectes que les microones tenen en la química de la vulcanització. Per tant, el principal objectiu d'aquesta tesi es basa en estudiar la vulcanització assistida amb microones des d'una nova perspectiva, centrant-se en els efectes d'aquesta radiació en els ingredients principals de les formulacions de cautxú, en el mecanisme de vulcanització, en la reticulació de la xarxa polimèrica i també en el procés de devulcanització.La primera part de la feina va consistir en desenvolupar i optimitzar tots els mètodes analítics necessàris per explorar totes les etapes del procés de vulcanització i identificar tots els intermedis formats. Estudis de Model Compound Vulcanization (MCV) utilitzant esqualè com a molècula model s'han realitzat per entendre millor la influència d'aquesta radiació en el mecanisme de la reacció, encara que alguns experiments també s'han realitzat amb mostres de cautxú natural. Tècniques com HPLC-MS, MALDI-TOF o GPC s'han utilitzat per caracteritzar les mostres de MCV, mentre que mesures d'inflament, de tensió-elongació, compressió i duresa s'han realitzat per caracteritzar les mostres de cautxú natural.Dos dels sistemes de vulcanització més comuns han estat estudiats (sulfenamides i tiurams). A més, s'ha donat un especial èmfasi a l'estudi de la influència de les microones en el sistema activador, intentant reduir el contingut de ZnO i cercar, a través de diverses estratègies, substituts més amigables amb el medi ambient. Finalment, tot el coneixement adquirit en aquests estudis s'ha utilitzat per optimitzar el comportament devulcanitzant del disulfur de difenil (DPDS) amb l'ajut de les microones, demostrant que les microones poden ajudar a avançar en la recerca d'una solució al problema del reciclatge dels residus de cautxú. / La vulcanización por microondas es un proceso maduro y no cabe duda sobre su eficiencia para producir artículos de caucho de alta calidad. Las microondas son conocidas no sólo por su capacidad de acelerar los procesos y aumentar la eficiencia de la transferencia energética, sino que también son capaces en ciertos casos de cambiar los caminos de reacción. Hay evidencias, basadas en cambios en propiedades físicas al comparar productos vulcanizados con el método convencional y con microondas, que indican que algunos cambios pueden suceder al trabajar con diferentes fuentes de calentamiento. Sin embargo, hay una falta de información sobre los efectos que las microondas tienen en la química de la vulcanización. Por lo tanto, el principal objetivo de esta tesis se basa en estudiar la vulcanización asistida por microondas desde una nueva perspectiva, centrándose en los efectos de esta radiación en los ingredientes principales de las formulaciones de caucho, en el mecanismo de vulcanización, en la reticulación de la red polimérica y también en el proceso de devulcanización.La primera parte del trabajo consistió en desarrollar y optimizar todos los métodos analíticos necesarios para explorar todas las etapas del proceso de vulcanización y identificar todos los intermedios formados. Estudios de Model Compound Vulcanization (MCV) utilizando escualeno como molécula modelo se han realizado para entender mejor la influencia de esta radiación en el mecanismo de la reacción, aunque algunos experimentos también se han realizado con muestras de caucho natural. Técnicas como HPLC-MS, MALDI-TOF o GPC se han utilizado para caracterizar las muestras de MCV, mientras que medidas de inflamiento, de tensión-elongación, compresión y dureza se han realizado para caracterizar las muestres de caucho natural.Dos de los sistemas de vulcanización más comunes han sido estudiados (sulfenamidas y tiuramos). Además, se ha dado un especial énfasis al estudio de la influencia de las microondas en el sistema activador, intentando reducir el contenido en ZnO y buscar, a través de diversas estrategias, substitutos más amigables con el medio ambiente. Finalmente, todo el conocimiento adquirido en estos estudios se ha utilizado para optimizar el comportamiento devulcanitzante del disulfuro de difenilo (DPDS) con ayuda de las microondas, demostrando que las microondas pueden ayudar a avanzar en la búsqueda de una solución al problema del reciclaje de los residuos de caucho. / Microwaves vulcanization is a mature process and there is no doubt about its efficiency on producing high quality goods. Microwaves are found not only to speed up the processing and increase the energy transfer efficiency, but also to be in some cases able to change reaction pathways. There are some evidences, based on changes in physical properties when comparing conventional and microwaves vulcanization, that suggest that some changes occur when working with different heating sources. However, there is a lack of information of the effects of MW in vulcanization chemistry. Therefore, the principal aim of this thesis consists of studying microwave-assisted vulcanization from a new perspective, focusing on the effects of this radiation in the main ingredients of a rubber compound, in the vulcanization mechanism, in the final crosslinked network and also in the devulcanization process.The first part of the work consisted in developing and optimizing all the analytical methods necessary to explore all the steps of vulcanization process and identifying all the intermediates formed. Model Compound Vulcanization (MCV) studies, using squalene as a model molecule, have been used to understand better the influence of this radiation in the reaction mechanism, even though some tests have been also performed in natural rubber samples. Techniques as HPLC-MS, MALDI-TOF or GPC have been used to characterize the MCV samples, whereas swelling measurements, stress-strain measurements, compression set or hardness have been used to characterized natural rubber samples. Two of the most common vulcanizing systems have been studied (using sulfenamide and/or thiuram accelerator types). In addition, a special emphasis has been given to the study of the microwaves influence on the activator system, trying to reduce ZnO contents and finding more environmental friendly substitutes through different strategies. Finally, all the knowledge acquired in all these studies has been used to optimize the devulcanizing behavior of diphenyl disulfide (DPDS) with the help of microwaves, proving that microwaves can help to advance in the search of a solution to the problem of waste rubber recycling.

Ces dernières années, la recherche de solutions au problème de l'élimination de déchets polymères, notamment les déchets issus de pneumatiques qui posent de graves problèmes environnementaux, connait un développement croissant. Dans ce contexte, ce projet de recherche a pour objectif de contribuer au développement et à la promotion de solutions innovantes qui font appel aux connaissances développées dans les domaines des nanotechnologies, de la science et l’ingénierie des matériaux nouveaux et du génie des procédés et des produits. Il s’agit plus particulièrement de d’étudier la possibilité de valoriser les déchets issus de pneumatiques en les utilisant comme matière première (en tant que agents de renfort ou agents de modification de la résistance aux chocs) pour l'élaboration de matériaux nanostructurés. Ce travail met l'accent sur l'étude des mélanges de polyéthylène haute densité (PEHD) contenant des particules d’argile (dispersées à l'échelle du nanomètre) et des déchets de caoutchouc issus de pneumatiques usagés (ou Ground Rubber Tire ou GRT). Il est attendu que ce matériau présente des propriétés typiques des mélanges de polymères appelés Vulcanisats Thermoplastiques (TPVs), résultant de la vulcanisation dynamique de la phase de caoutchouc pendant le traitement à l'état de fondu (extrusion). Dans le système étudié, la matrice est le PEHD et la phase dispersée de la poudrette de pneu, préalablement dévulcanisée par micro-ondes. L'argile dispersée dans la phase de la matrice, agit comme un agent compatibilisant entre les phases du mélange et comme agent de renforcement, apportant une amélioration des propriétés mécaniques des matériaux préparés. La caractérisation des mélanges met l'accent sur leur morphologie et leur structure ainsi que sur leurs propriétés rhéologiques, thermiques et mécaniques. Une étude approfondie de l'évolution de la morphologie du mélange au cours de l’extrusion a été effectuée car ce paramètre est la clé pour optimiser le procédé et obtenir les meilleures propriétés pour le matériau final. Ceci représente la contribution plus importante de ces travaux de recherche. / The main objective of this work was the production of dynamically revulcanized blends containing HDPE and GTR devulcanized by microwaves. It comes against a big global problem which is the waste disposal of vulcanized elastomers, especially tires, which bring with them serious environmental and public health problems, since these materials require long periods of time to degrade naturally due to their structure of cross-linkings, and the presence of stabilizers and other additives in its formulation. A way of using the GTR that has been widely studied by researchers is as polymer blends in which one of the phases is a thermoplastic polymer. In this context, the role of elastomers devulcanization is to increase the interaction between raw and recycled material, reducing the degradation of properties of the finished product with its incorporation and making it possible the increase of the recycled rubber amount in the compound recycled rubber/thermoplastic. The devulcanization transformes devulcanized elastomer into a fluid material, allowing a better control of the particle size during the mixing process of the blend by breaking processes in the application of high shear rates. In addition, by becoming a fluid material, it is possible the incorporation of a higher amount of elastomer to the thermoplastic without great damage to its processability. However, the literature does not have works in which the study of the processing parameters of dynamically revulcanized blends containing devulcanized elastomer, as well as the influence of addition of clays from different shapes (lamellar and tubular) on their final properties, especially on rheological properties, which sets out the present work. Summarizing, this work aims to propose a possible solution to the problem of solid waste disposing by producing a dynamically revulcanized blend containing HDPE and GTR devulcanized by microwaves, in addition to decrease some gaps observed currently in the literature from the obtained results.

Waste management of vulcanized rubber is a serious environmental problem as the molecular structure formed during the process complicates recycling. Due to this, researchers have developed a process that can break the strong bonds and return the rubber to its original state. This process is called devulcanization and is developed for the tire industry due to the large amount of waste formed from this sector. This rubber is vulcanized with sulfurs like 90 % of other rubber products. However, there exist other products that are vulcanized with peroxides where much less research has been done. Due to this, it is unclear if devulcanization is possible as a different type of bond is formed in the vulcanization process. This work therefore investigates the possibilities with recycling by devulcanization of peroxide cured rubber where a collaboration is done with Roxtec International AB. The work also investigates the possibilities with reuse of the cooperating partner’s particular rubber and how everything can be implemented to understand the efficiency of these two waste management strategies and to share knowledge.  The used method for this work is a combination of the Participatory Action Research (PAR) and the Design thinking (DT) framework. A systematic literature review has also been conducted to collect relevant material for one of the research questions. The result showed that there exist many methods and possibilities with devulcanization of peroxides if sufficient energy is provided. However, the quality of the reclaimed rubber will be lacking as the bonds in the polymers main chain are degraded which affects the mechanical properties. Due to this only a small percentage can be reused by mixing it with virgin rubber. The efficiency for peroxides is therefore lower than for sulfurs. Regarding reuse many alternative usage areas were brainstromed but once the concepts were evaluated against the limitations with the material, the needs and the sustainability factor, only few solutions survived. The winning concept became a punching bag filled with granulated rubber crumbs. When investigating how everything can be implemented it turned out that a lot of effort is needed. For example, to get favorable results, the solution will require the punching bag company to also want to work towards sustainability by adapting take back systems. Devulcanization will then require that the waste is sorted which requires a big investment in both time and money to achieve. The conclusion of this work is that devulcanization and reuse is possible and the developed system solution can take care of parts of the waste. However, the possibilities are limited and to get rid of all the waste and develop a long-term solution that is both sustainable and further prepared for the future, more actions are needed. It is therefore of high interest to start investigating the possibilities with a new material that is easy to recycle or are degradable. / Avfallshantering av vulkaniserat gummi är ett allvarligt miljöproblem eftersom den molekylära strukturen som bildas under processen komplicerar återvinning. På grund av detta har forskare utvecklat en process som kan bryta de starka bindningarna och återställa gummit till sitt ursprungliga tillstånd. Denna process kallas devulkanisering och är främst utvecklad för däck-industrin på grund av den stora mängden avfall som bildas från denna sektor. Detta gummi vulkaniseras med svavel som 90% av andra gummiprodukter. Det finns dock andra produkter som vulkaniseras med peroxider där mycket mindre forskning har gjorts. På grund av detta är det oklart om devulkanisering är möjlig eftersom en annan typ av bindning bildas i vulkaniseringsprocessen. Detta arbete undersöker därför möjligheterna med återvinning genom devulkanisering av peroxid härdat gummi där ett samarbete görs med Roxtec International AB. Arbetet undersöker också möjligheterna med återanvändning av samarbetspartners specifika gummi spill och hur allt kan implementeras för att förstå effektiviteten i dessa två avfallshanterings strategier och för att sprida kunskap. Den använda metoden för detta arbete var en kombination av PAR (Participatory Action Research) och design thinking (DT). En systematisk litteraturstudie har också genomförts för att samla in relevant material för en av forskningsfrågorna. Resultatet visade att det finns många metoder och möjligheter för devulkanisering av peroxider om tillräcklig energi tillhandahålls. Dock kommer kvalitén på det återvunna gummit att försämras markant då bindningarna i polymerens huvudkedja bryts vilket påverkar de mekaniska egenskaperna. På grund av detta kan endast en liten andel återanvändas genom att blanda med jungfruligt gummi. Effektiviteten för peroxider är därför lägre än för svavel. När det gäller återanvändning, brainstormades många alternativa användningsområden, men när koncepten utvärderades mot begränsningarna med materialet, behoven och hållbarhetsfaktorer överlevde bara ett fåtal lösningar. Det vinnande konceptet blev en slagsäck fylld med granulerat gummi. När det undersöktes hur allt kan implementeras visade det sig att det krävs mycket ansträngningar. Till exempel, för att få gynnsamma resultat kommer lösningen att kräva att boxsäck företaget också vill arbeta för hållbarhet genom att anpassa take back system. Devulkaniserings-processen kommer även kräva att avfallet sorteras vilket kräver en stor investering i både tid och pengar för att uppnå. Slutsatserna av detta arbete är att devulkanisering och återanvändning är möjligt och den utvecklade systemlösningen kan ta hand om delar av avfallet. Men möjligheterna är begränsade och för att bli av med allt avfall och utveckla en långsiktig lösning som både är hållbar och ytterligare förberedd för framtiden, kommer fler åtgärder att behövas. Det är därför av stort intresse att börja undersöka möjligheterna med ett nytt material som är lätt att återvinna eller är nedbrytbart.