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Leite P.R.S.,Federal University of Rio de Janeiro | Soares B.G.,Federal University of Rio de Janeiro | Sirqueira A.S.,University Estadual da Zona Oeste
Journal of Applied Polymer Science | Year: 2011

Polypropylene (PP)/styrene-butadiene rubber blends were studied with special attention given to the effects of the blend ratio and dynamic vulcanization. Dicumyl peroxide (DCP) was used as the curing agent in combination with N,N′-m-phenylene bismaleimide (BMI) as the coagent for the curing process. Outstanding mechanical performance, especially with regard to the elongation at break, and better resistance to compression set were achieved with the dynamic vulcanization; this indicated that the DCP/BMI system also acted as a compatibilizing agent. This phenomenon was also confirmed by Fourier transform infrared spectroscopy of the insoluble material, the crystallinity degree of the PP phase (as investigated by X-ray diffractometry), and scanning electron microscopy. The dynamic mechanical properties of the nonvulcanized and vulcanized blends were also investigated. The aging resistance of the blends was also evaluated. © 2010 Wiley Periodicals, Inc. Source

Angulo-Meza L.,Federal University of Fluminense | Soares-De Mello J.C.C.B.,Federal University of Fluminense | Gomes S.F.,University Estadual da Zona Oeste
DYNA (Colombia) | Year: 2016

Data Envelopment Analysis is a non-parametrical approach for efficiency evaluation of so-called DMUs (Decision Making Units) and takes into account multiple inputs and outputs. For each inefficient DMU, a target is provided which is constituted by the inputs or outputs levels that are to be attained for the inefficient DMU to become efficient. However, multiobjective models, known as MORO (Multiobjective Model for Ratio Optimization) provide a set of targets for inefficient DMU, which provides alternatives among which the decision-maker can choose. In this paper, we proposed an extension of the MORO models to take into account non-discretionary variables, i.e., variables that cannot be controlled. We present a numerical example to illustrate the proposed multiobjective model. We also discuss the characteristics of this model, as well as the advantages of offering a set of targets for the inefficient DMUs when there are non-discretionary variables in the data set. © The author; licensee Universidad Nacional de Colombia. Source

Silva A.d.C.,Federal University of Rio de Janeiro | Senra J.D.,Federal University of Rio de Janeiro | Aguiar L.C.S.,Federal University of Rio de Janeiro | Simas A.B.C.,Federal University of Rio de Janeiro | And 3 more authors.
Tetrahedron Letters | Year: 2010

In this work, we present ligand-free Suzuki cross-coupling reactions in PEG 300 under thermal conditions at 55 °C with good yields of conversion; better results were obtained with low reaction time. In 1 hour, 1-iodo-4-nitrobenzene and phenylboronic acid reached 98% of the yield and 9700 of TON. Better results were obtained with Pd(0) sources. The reaction system was recycled up to three times with good activity. © 2010 Elsevier Ltd. All rights reserved. Source

Magioli M.,Federal University of Rio de Janeiro | Soares B.G.,Federal University of Rio de Janeiro | Sirqueira A.S.,University Estadual da Zona Oeste | Rahaman M.,Indian Institute of Technology Kharagpur | Khastgir D.,Indian Institute of Technology Kharagpur
Journal of Applied Polymer Science | Year: 2012

This work investigates the effect of different preparation routes including mechanical mixing and in situ polymerization of aniline on the electromagnetic interference shielding effectiveness (EMI SE) over the X-band (8-12 GHz) frequency range for polyaniline doped with dodecylbenzene sulfonic acid (PAni.DBSA) filled in styrene-butadiene-styrene triblock copolymer matrix. The dc conductivity and dielectrical properties were also investigated. For all systems, the electrical conductivity, dielectric constant, and EMI SE increased with the increase in the concentration of PAni.DBSA. Blends prepared by the in situ polymerization exhibited higher conductivity and dielectric constant and better EMI SE characteristics than the physical blends with similar amount of PAni.DBSA. EMI SE value as high as -35 dB has been achieved with about 30% of PAni.DBSA prepared by the in situ polymerization. Regarding physical blends, those involving PAni.DBSA prepared by a redoping process displayed better EMI SE. For all systems under consideration, the conductivity and EMI SE bear an exponential relationship that can be represented by a master curve. Copyright © 2012 Wiley Periodicals, Inc. Source

Magioli M.,Federal University of Rio de Janeiro | Sirqueira A.S.,University Estadual da Zona Oeste | Soares B.G.,Federal University of Rio de Janeiro
Polymer Testing | Year: 2010

Thermoplastic elastomer blends consisting of 30% polypropylene and 70% ground rubber tire, pure or combined with virgin styrene-butadiene copolymer, were successfully prepared through a dynamic vulcanization process, involving dicumyl peroxide and N,N′-m-phenylene-bis-maleimide (BMI), in different proportions. The blends have shown excellent ultimate tensile strength and elongation at break, comparable with several others TPV systems, and also good reprocessing, which becomes useful for several potential applications. The blends were also characterized in terms of fatigue properties, morphology and dynamic mechanical properties. The tensile properties after fatigue stress decreased but this behavior was less significant for PP/GTR vulcanized blends. The effects of the dynamic vulcanization and the presence of GTR on the degree of crystallinity of the PP phase were also evaluated by differential scanning calorimetry analysis. © 2010 Elsevier Ltd. All rights reserved. Source

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