Pernambuco Institute of Technology

Recife, Brazil

Pernambuco Institute of Technology

Recife, Brazil

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Da Silva H.M.,Federal University of Pernambuco | Da Silva H.M.,Pernambuco Institute of Technology | Vilela O.C.,Federal University of Pernambuco | Fraidenraich N.,Federal University of Pernambuco | Veissid N.,National Institute for Space Research
30th ISES Biennial Solar World Congress 2011, SWC 2011 | Year: 2011

It is evaluated the performance of a CPV multijunction (MJ) cell (InGaP/InGaAs/Ge) of 1.0 cm2 area, for concentration rates varying from 1 up to 122X. The parameters which characterize the cell are extracted from experimental characteristic curves using the one diode model. Special attention is given to the series resistance, which affects significantly the cell performance. Results obtained show that the procedure adopted is considerably consistent, enabling to obtain a general picture of solar cell behavior in spite of large temperature and irradiance experimental variations. A large value of series resistance (3.8 Ω) is observed for low concentration values. This resistance decays rapidly, attaining a stable value for high concentrations (0.024 Ω). Average conversion efficiencies of 35% have been measured when converted to temperatures of 47°C. Series resistance obtained for high concentrations (0.024 Ω) limit the concentration rate corresponding to maximum efficiency to values between 243 and 278. Higher efficiencies with higher concentrations, probably, require further reduction of series resistance.

Wellen R.M.R.,Pernambuco Institute of Technology | Canedo E.L.,Pernambuco Institute of Technology | Lima C.A.V.,Federal University of Pernambuco | Junior I.C.A.,Federal University of Pernambuco | And 2 more authors.
Materials Research | Year: 2015

Mechanical properties, morphology and nonisothermal crystallization of poly(3-hydroxybutyrate) (PHB) and blends of PHB and polystyrene (PS) were studied by tensile tests, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). A two-phase structure composed by a PHB matrix and nearly spherical particles of PS was clearly noticed in SEM images. The presence of small amounts (0.5% to 3%) of amorphous PS affected the crystallinity of PHB, being more evident when high cooling rates were applied. The kinetics of nonisothermal crystallization was modeled according to Ozawa equation. The dependence of Ozawa parameters on temperature followed the same trend for PHB and PHB/PS blends; model parameters were found to be lower for the blends than for the neat PHB. © 2015.

Wellen R.M.R.,Pernambuco Institute of Technology | Rabello M.S.,Federal University of Campina Grande | Fechine G.J.M.,University of Sao Paulo | Canedo E.L.,Pernambuco Institute of Technology
Polymer Testing | Year: 2013

This work is concerned with the melting behaviour and accuracy of differential scanning calorimeter (DSC) analyses of poly(3-hydroxybutyrate) (PHB), a semi-crystalline thermoplastic polymer completely biodegradable and biocompatible, and obtained from renewable resources. Melting parameters of PHB were determined for the first fusion event applying standard experimental procedures for thermal analysis, using heating rates ranging between 1 °C/min and 20 °C/min. The analyses of DSC energy flow scans showed a complex melting peak that may be resolved into three elementary peaks having different intensities at different melting temperatures. Peak temperatures depend on heating rate, while the total crystallinity detected was independent of the rate. A study of 24 DSC runs showed good temperature reproducibility (±0.5 °C), but poor reproducibility of mass crystallinity (±10%). © 2012 Elsevier Ltd. All rights reserved.

Wellen R.M.R.,Federal University of Paraiba | Canedo E.L.,Federal University of Campina Grande | Canedo E.L.,Pernambuco Institute of Technology
Journal of Materials Research | Year: 2016

Three classical methods (Pseudo-Avrami, Ozawa, and Mo models) were used to correlate nonisothermal melt and cold crystallization kinetics data of neat poly(3-hydroxybutyrate) (PHB) and PHB/carbon black compounds, measured by differential scanning calorimetry. The applicability of the three models was tested comparing model predictions with experimental data. Results suggest that Pseudo-Avrami model fits the experimental data well. Ozawa model does not fit data well, as verified by the large uncertainties and unphysical values of the fitting parameters. Mo model may be considered adequate if moderately deviations could be tolerated. Datasets of all compositions are included as the Supplementary Information. © 2016 Materials Research Society.

Costa A.R.M.,Federal University of Campina Grande | Almeida T.G.,Federal University of Campina Grande | Silva S.M.L.,Federal University of Campina Grande | Carvalho L.H.,Federal University of Campina Grande | And 2 more authors.
Polymer Testing | Year: 2015

This contribution is concerned with degradation and chain extension in poly(butylene-adipate-terephthalate), PBAT, compounded in a laboratory internal mixer with an epoxydic chain extender additive. Weight-average mass change during melt processing was estimated from temperature-torque-time data recorded by the equipment. The effect of the additive was found to be strongly dependent on processing temperature, and weakly dependent on concentration. Molar mass more than doubled at 230°C with 2% additive. Long induction times and catastrophic failure to mix, occasionally observed with oligomeric additives processed in internal mixers, are discussed. Possible implementation of the procedure for real-time estimate of chain extension is also discussed. © 2015 Elsevier Ltd.All rights reserved.

Duarte I.S.,Federal University of Campina Grande | Tavares A.A.,Federal University of Campina Grande | Lima P.S.,Federal University of Campina Grande | Andrade D.L.A.C.S.,Federal University of Campina Grande | And 4 more authors.
Polymer Degradation and Stability | Year: 2016

Poly (ethylene terephthalate) (PET) is widely used in several segments of the plastic industry and PET-based products are extensively recycled. However, PET degrades during processing and use, which results in a decrease of molar mass and reduction of the material's performance. Degradation particularly affects recycled materials, subjected to repeated processing and use cycles, this limiting the applications of recycled PET. Chain extender additives rejoin polymer chain segments, compensate molar mass reduction due to degradation, and may be used to further increase molar mass. In the present work, an epoxidic multifunctional oligomer (Joncryl), recommended for use with condensation polymers was tested for chain extension of virgin and recycled PET. Molar mass decrease (degradation) or increase (chain extension) during processing in a laboratory internal mixer may be related to torque and temperature variations reported by the instrument. Here molar changes during processing were considered in terms of the chain extension additive concentration (0-1.5%) and the nominal rotor speed (30 rpm-120 rpm) in samples of bottle-grade virgin PET and postconsumer recycled PET. It was found that the molar mass changes depend strongly on additive content; 0.5% and 1.0% chain extender levels were sufficient to compensate the mild degradation observed in unadditivated samples. Reprocessing tests, with and without further additivation, showed that extra additivated PET (1.5% additive concentration) preserves chain extension capabilities to sustain reprocessing without molar mass decrease. The procedure adopted allows inline testing of additive effectiveness. © 2015 Elsevier Ltd. All rights reserved.

Vitorino M.B.C.,Federal University of Campina Grande | Cipriano P.B.,Federal University of Campina Grande | Wellen R.M.R.,Federal University of Paraiba | Canedo E.L.,Federal University of Campina Grande | And 2 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2016

Poly(3-hydroxybutyrate) (PHB)/babassu compounds were prepared in a laboratory internal mixer with 10, 30, and 50 % by mass of fiber content. Nonisothermal melt crystallization behavior of PHB/babassu compounds was investigated using differential scanning calorimetry, and crystallization parameters were determined at cooling rates ranging between 2 and 32 °C min−1. Adding babassu fiber affected the melt crystallization behavior of PHB, and increasing filler content from 10 to 30 % has significant effects on the thermal characteristics of the system. Further increase in filler content from 30 to 50 % filler content has no effect on crystallization temperature and rate, but it has important positive consequences, once there is a considerably latitude in choosing the actual filler level in highly loaded PHB/babassu compounds without affecting processing characteristics. The melt crystallization kinetics of PHB/babassu compounds was analyzed by three empirical models widely used to represent nonisothermal polymer crystallization data: Pseudo-Avrami, Ozawa, and Mo. Kinetics analyses indicate that the Pseudo-Avrami model represented well the experimental data for both compounds in a wide interval of temperature, conversion, and cooling rates; the Ozawa model with two different sets of parameters, for low and high cooling rates, was found to correlate the data equally well, but over limited ranges of the variables, and the model proposed by Mo and collaborators did not adequately represent the experimental data for the systems and conditions tested. © 2016 Akadémiai Kiadó, Budapest, Hungary

Ferreira K.R.M.,Federal University of Campina Grande | Andrade D.L.A.C.S.,Federal University of Campina Grande | Canedo E.L.,Federal University of Campina Grande | Canedo E.L.,Pernambuco Institute of Technology | And 2 more authors.
Materials Science Forum | Year: 2015

In this study, the influence of type and amount of organoclay in the morphology of the polymer blend PP/EPDM is evaluated. Pure and filled mixtures were prepared by melt intercalation in an internal mixer. The morphology of the hybrids was evaluated by X-ray diffraction and scanning electron microscopy. The results showed that the incorporation of the organophyllic clay to the PP/EPDM blend resulted in new interfacial interactions between components, which contributed to a decrease in the size of the dispersed phase and the compatibility of the blends. Therefore, organoclays may be employed to compatibilize polymeric blends, replacing conventional compatibilizers. © (2015) Trans Tech Publications, Switzerland.

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