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Navegando por Autor "Melo, Tomas Jeferson Alves"

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    Artigo
    Effect of alumina on the properties of poly(methyl methacrylate)/alumina composites obtained by melt blending
    (SAGE Publications, 2019-04-28) Ito, Edson Noriyuki; Arimateia, Rafaela R.; Hanken, Ruth B. L.; Oliveira, Akidauana D. B.; Agrawal, Pankaj; Freitas, Normanda L.; Silva, Erik dos Santos; Melo, Tomas Jeferson Alves
    In this work, the properties of poly(methyl methacrylate) (PMMA)/alumina composites prepared by melt blending were evaluated. Two types of alumina were used: one, that was synthesized (ALS) by the combustion reaction method, and the other that is commercially available (ALC). Extrusion proved to be a good processing technique for obtaining PMMA/alumina composites. PMMA/alumina composites containing ALC presented higher alumina average particles size. The addition of alumina to PMMA substantially decreased the wear index and increased the scratch resistance. The mechanical properties of the composites containing ALS were similar to those containing ALC. The storage modulus (E0) increased with the addition of alumina to PMMA. The zero shear viscosity (h0) values of the composites containing ALC were higher than those of the composites containing ALS
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    Artigo
    Hybrids nanocomposites based on a polymer blend (linear low-density polyethylene/poly(ethylene-co-methyl acrylate) and carbonaceous fillers (graphene and carbon nanotube)
    (Wiley, 2020-10-29) Ito, Edson Noriyuki; Nunes, Mário A. B. S.; Matos, Bruno R. de; Silva, Glaura G.; Melo, Tomas Jeferson Alves
    Interfacial or separate phase location of carbonaceous nanofillers (graphene and carbon nanotubes) in polymer blends with co-continuous phases can lead to double percolation behavior, significantly increasing rheological and electrical properties. The prediction of the morphology and the location of the nanofillers has been used as a tool to evaluate the proprieties of co-continuous polymer blends. This work aims to highlight the superior conductivity levels achieved using a low amount of carbon-based fillers, by the proper selection in a multiphase polymer matrix as a template for controlled dispersion and spatial distribution of the nanoparticles, offering a compromise between easy processability and enhanced performance. Here, two polymers (linear low-density polyethylene [LLDPE] and ethylene-co-methylacrylate [EMA]) and their co-continuous blend (LLDPE/EMA) were loaded with nanofillers (few-layer graphene [FLG], few-walled carbon nanotube [FWCNT]) via continuous melt mixing in twin-screw extrusion, separate and simultaneously. It was observed that the addition of the nanofillers changed the co-continuity of the blend, with the probable migration of the nanofillers from the EMA (hydrophilic) phase to the LLDPE (hydrophobic) phase. Rheological percolation occurred preferentially in blends containing FWCNT and FLG/FWCNT. Electrical conductivity was observed in all compositions, with higher electrical conductivity being noticed in hybrids
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    Artigo
    Influence of amine groups in the chemical structure of photochromic dyes on the rheological and mechanical properties of poly(methyl methacrylate) (PMMA)
    (Elsevier, 2017-07) Ito, Edson Noriyuki; Rego, José Kaio Max Alves do; Nascimento, José Heriberto Oliveira do; Agrawal, Pankaj; Melo, Tomas Jeferson Alves; Costa, Maria Carolina Burgos Costa do
    Polymer modification has been used as a means to improve the adhesion/bonding of compounds and/or particles to polymer chains, but this goal is not always achieved. Some compounds contain naturally reactive groups which, in contact with the polymer, can modify its properties. This work focused on the rheological (torque and parallel plates rheometry) and mechanical (tensile and impact) characterization of PMMA containing the DV31, DBL3 and DB79 aminic dyes and the DR73 inert dye. The rheological results indicated that the final torque (torque rheometry) varied in response to increasing dye concentrations, and that the various dyes under study exhibited distinct behaviors (parallel plates rheometry). The mechanical tests revealed that, overall, the effect of the dyes on the properties of PMMA was negligible, except for DV31, that led to the decrease in the impact strength, possibly due to the bond between chains or segments of chains of the polymer. The presence, amount and type of amine in the dyes gave rise to significant rheological changes in PMMA because of the reactivity between the amine and the ether group of PMMA
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    Artigo
    Nanocompósitos de polietileno/argila bentonita nacional: influência da argila e do agente compatibilizante PE-g-MA nas propriedades mecânicas e de inflamabilidade
    (Associação Brasileira de Polímeros, 2008-06) Ito, Edson Noriyuki; Brito, Gustavo F.; Oliveira, Amanda D. de; Araújo, Edcleide Maria; Melo, Tomas Jeferson Alves; Barbosa, Renata
    Nanocompósitos de polietileno de alta densidade/argila bentonita nacional foram preparados por intercalação por fusão. A influência da adição da argila sem tratamento e da argila tratada com o sal quaternário de amônio Cetremide e do polietileno graftizado com anidrido maléico (PE-g-MA) como agente compatibilizante foi avaliada. Os sistemas obtidos foram caracterizados por inflamabilidade, propriedades mecânicas e reológicas, difração de raios X e microscopia eletrônica de transmissão. Os resultados de difração de raios X e microscopia eletrônica de transmissão indicaram a obtenção de nanocompósitos com estruturas parcialmente esfoliadas e/ou intercaladas que conduziram ao aumento do módulo de elasticidade e do valor do torque. O teste de inflamabilidade mostrou que a adição da argila na matriz polimérica e a presença do PE-g-MA retardaram a velocidade de queima do sistema, ou seja, diminuíram a inflamabilidade do PE puro. Em geral, o sistema contendo o agente compatibilizante (PE-g-MA) exibiu melhorias na estabilidade térmica e nanocompósitos parcialmente esfoliados foram formados, quando comparados à matriz de polietileno de alta densidade. O polietileno graftizado com anidrido maléico não apenas promoveu a esfoliação da argila, mas também facilitou a adesão carga-matriz, obtendo-se com isso melhorias nos resultados mecânicos do sistema
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