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For a sustainable development, recycling is a very important step, which, beyond saving the use of natural resources, can also be a solution for low-income families, providing them earnings. Recycling is also considered a category of green chemistry and contributes to the reduction of pollution, bringing the improvement to the public health. However, recycling of a material trying to contribute to the environment will not bring positive results if the final properties of the recycled material do not point to an application that is viable. In this sense, the aim of this work is to present a comprehensive study of the revulcanized ground tire rubber samples, previously devulcanized by the action of the microwaves under different exposure times. It is extremely important to know in depth the modifications that occurred in the recycled material during all the stages of the recycling process to which the material was subjected, in order to select the ideal application for the recycled material. The obtained results pointed out to modifications as a result of the revulcanization process, such as in the chemical structure, composition, thermal stability, and morphology.

The recycling of waste rubber has considerable significance in terms of environmental protection and energy conservation. Considering that most of the relevant literature is concerned with tire recycling, the objective of this study is to develop and characterize styrene-butadiene rubber composites containing only industrial rubber scraps devulcanized by microwave. The styrene-butadiene rubber extruded profile scraps were collected and ground under ambient conditions. The obtained powder styrene-butadiene rubber-r was physically, thermally, and chemically characterized. From the devulcanized styrene-butadiene rubber-r two composites were prepared, varying the exposure time of the powder in the microwave (3 and 4 min). These composites were compared to a control sample supplied by the industry from which the styrene-butadiene rubber extruded profile scraps were collected. Vulcanization parameters were determined by oscillatory disk rheometry. Vulcanized composites were characterized by crosslink density and physical-mechanical properties (Shore A hardness, tensile and tear strength, and compression set) before and after a postcure process. The mechanical properties of the compositions were ∼25% for tensile strength and 41% for tear strength compared to the control sample. The results for the crosslink density verified those for the mechanical properties of the composites.

The influence of rubber devulcanization by microwaves in the reversion behavior is still modestly explored in the literature. The reversion occurs due to thermal degradation of unstable crosslinkings formed during the vulcanization process. This phenomenon results in poor final mechanical properties of the artifacts. In this work, some formulations based on natural rubber (NR) with the incorporation of NR devulcanized by microwaves at different exposure times to the microwaves were vulcanized by compression molding at the same temperature and time used for the study of their vulcanization characteristics, in order to correlate the properties obtained and understand the influence of the reversion on the mechanical properties. The results showed that levels of devulcanization/degradation of the recycled phase, as well as the additional heating time influenced on the behavior of reversion and, consequently, on the mechanical properties. the influence of density and crosslinking type in the mechanical properties of rubber has been studied by various authors, 4,6,7 since the stress-strain measurement is an indirect method for determining the crosslinking density. 5Currently, a big global problem is related to disposal of solid urban residues, and materials able to make this problem much worse are the vulcanized/cured elastomers. In the same way, the search for processes and/or sustainable materials is of great value, and it is directly related to the solution of this problem, since the use of recycled materials can reduce such problem. In addition, recycling not only protects the environment, but also saves the limited petroleum resources from which the raw material originates, 8 also being a source of income for many families around the world. The recycling method used in this work is the devulcanization by microwaves.Devulcanization is a way of providing energy to destroy, total or partially, the three-dimensional network formed during vulcanization. 9 Devulcanization by microwaves is a well-established recycling technique of vulcanized elastomers. Among its

SBR and EPDM extruded profile scraps are ground under ambient conditions for further utilization in recycling and reclaiming processes. The obtained powders (SBR-r and EPDM-r, respectively) are physically, thermally, and chemically characterized and the results are analyzed as for its suitability for reuse methods. It is possible to obtain powdered SBR and EPDM rubber with irregular shape and high surface roughness. The grinding process has not deteriorated the material. The obtained powder is suitable for utilization in new formulations and in regeneration processes.

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Resumo: Uma alternativa para as empresas geradoras de resíduos elastoméricos é a incorporação dos mesmos em suas formulações. Esse trabalho tem como objetivo preparar compósitos a partir da incorporação de resíduos industriais de SBR (copolímero de butadieno-estireno) e de EPDM (terpolímero de etileno-propileno-dieno), em formulação ASTM específi-ca para cada tipo de elastômero. Foram avaliadas as propriedades reométricas, mecânicas e morfológicas dos compósitos desenvolvidos. A incorporação do resíduo permitiu a obtenção de produtos que vulcanizam em menores tempos quando comparados a composições sem resíduo. A quantidade de resíduo, para o melhor resultado de resistência à tração foi de 37 e de 196 phr para os compósitos com SBR e EPDM, respectivamente. As micrografias de MEV corroboraram os resultados mecânicos dessas composições, indicando melhor homogeneidade do resíduo na respectiva matriz elastomérica. Palavras-chave: Resíduo de SBR, resíduo de EPDM, compósitos elastoméricos, propriedades mecânicas, reometria. Cure Characteristics, Mechanical Properties and Morphology of Composites Developed with Addition of Elastomeric Vulcanized Ground ScrapsAbstract: One alternative for elastomeric scraps generation is its incorporation in conventional formulations in the industry itself. In this work, compositions with incorporation of SBR (styrene butadiene rubber) and EPDM (ethylene propylene diene rubber) industrial scraps, in specific ASTM formulation for each elastomer, were prepared. Rheometric characteristics, mechanical properties and the morphology of the compounds developed were evaluated. With the ground scraps incorporation the vulcanization time decreases, comparing with compounds without ground scraps. The amount of scraps for the best tensile strength properties was 37 and 196 phr for SBR and EPDM compositions, respectively. Micrographs corroborated the mechanical results, indicating the best homogeneity of the scraps in the elastomeric matrix for these compositions. Keywords: SBR ground scraps, EPDM ground scraps, elastomeric compounds, mechanical properties, cure characteristics. IntroduçãoArtefatos elastoméricos são utilizados nas mais diferentes indústrias como a automobilística, a calçadista, a hospitalar, entre outras. A ampla utilização em pneumáticos tem como conseqüência, a grande geração de resíduos pós-consumo que constitui um sério problema ambiental [1,2] .É de conhecimento que os polímeros termoplásticos apresentam degradação lenta e que nos elastômeros esta degradação lenta é potencializada pela presença de ligações cruzadas e de outros aditivos como antioxidantes, antiozonantes, que dificultam o seu reaproveitamento [1] . Segundo Sreeja [3] , apenas 8 a 12% dos resíduos poliméricos são de polímeros termoplásticos, enquanto que o restante são elastômeros, representados principalmente pelos pneus pós-consumo [4][5][6][7] .Uma forma de reutilização desses resíduos elastoméri-cos, após transformá-los em pó, é como carga em novas formulações. Este procedimento traz como vantagem o baixo custo...

Recycling is a process toward sustainable development. However, it does not do any good to recycle a material trying to contribute to the environment, if the final properties of the recycled material do not point to a feasible application. In this sense, the purpose of the present study is to evaluate the kinetics parameters of the revulcanization reaction of ground tire rubber (GTR) devulcanized by microwaves using rheological (ODR) and differential scanning calorimetry (DSC) methods. For ODR, torque versus time curves was obtained at 160, 170, 180, 190, and 200 °C and simulated. In general, occurred a decrease in activation energy values upon microwaves exposure time but all the samples showed an autocatalytic model from simulation curves. For DSC, three different models were used: Kissinger, Ozawa, and Flynn-Wall-Ozawa. All of the methods showed a trend to decrease the activation energy by microwave exposure time as noticed in the rheological curves. Among the reasons, the carbon black and the viscosity of the system are the main contributors; the former by radiation tends to oxidize and facilitates the degradation process, and the latter achieves more facility to chain mobility, reducing the activation energy.