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Artigo A new method for obtaining adsorption isotherms on colloidal suspensions via electrokinetic sonic amplitude measurement(2005-12-06) GUIMARAES, K. L.; CASTRO, R. H. R.; GOUVEA, D.The standard methods for obtaining adsorption isotherms on colloidal suspensions are usually very time consuming and involve a large number of steps and assumptions that increase the experimental errors. In this work, an alternative method is proposed to evaluate the adsorption behavior of electrostericstabilized systems based on electrokinetic sonic amplitude signal measurements. The new method, entitled "zeta-sorption", is noticeably less time-consuming when compared to conventional procedures but showed great precision and reliability confirmed by comparison with data obtained from conventional routes on alumina-polyacrylate and alumina-citric acid aqueous suspensions. The experimental conditions that restrict the applicability of the new method were identified and justified by discussing the possible ion exchanges. © 2005 American Chemical Society.Artigo A study of PP/PET composites: Factorial design, mechanical and thermal properties(2016) Nonato R.C.; Bonse B.C.© 2016 Elsevier LtdDue to the economic importance of polypropylene (PP) and polyethylene terephthalate (PET), and the large amount of composites made with PP matrix and recycled PET as reinforcing material; an investigation was performed regarding the mechanical and thermal behavior of PP composites containing recycled polyethylene terephthalate fibers (rPET). Interfacial adhesion between the two materials was achieved by adding a compatibilizer, maleic anhydride grafted polypropylene, PP-g-MA. Mechanical behavior was assessed by tensile, flexural, impact and fatigue tests, and thermal behavior by HDT (Heat Deflection Temperature). Fractured surfaces and fiber were investigated by scanning electron microscopy. Multiple regression statistical analysis was performed to interpret interaction effects of the variables. Tensile strength, tensile modulus, flexural strength, flexural modulus and HDT increased after rPET fiber incorporation while strain at break, impact strength and fatigue life decreased. Addition of compatibilizer increased tensile strength, flexural strength and flexural modulus, fatigue life and HDT while tensile modulus, strain at break and impact strength decreased. However, at low fiber content, the impact strength increased, probably due to nucleation effects on PP.Artigo Abiotic thermo-oxidative degradation of high density polyethylene: Effect of manganese stearate concentration(2017) Antunes M.C.; Agnelli J.A.M.; Babetto A.S.; Bonse B.C.; Bettini S.H.P.© 2017 Elsevier LtdThe effect of pro-degradant manganese (Mn) stearate concentration on the oxidative abiotic degradation of high-density polyethylene (HDPE) was investigated in thermo-oxidative tests at three temperatures (60, 70 and 80 °C) over time. Degradation monitoring was carried out, by determining carbonyl indices (CI), using infrared spectroscopy (IR), and by assessing molar masses and their distributions, using size exclusion chromatography (SEC) and tensile tests to assess mechanical properties. Deconvolution analyses of the absorbance bands obtained in the carbonyl region were performed to quantify the functional groups originated from degradation. Similar levels of degradation (equivalent molar mass and oxidation values) were obtained regardless of the investigated manganese concentration (50, 200 and 400 ppm). However, the results indicate that increasing Mn concentration may reduce the induction time for carbonyl formation. Deconvolution of the carbonyl region in IR spectra (between 1800 and 1650 cm−1) indicates that the addition of Mn results in increase in the concentration of oxidized functional groups (ketones, carboxylic acids, lactones, etc.) and that relationship between these groups varies depending on whether manganese stearate is present or not.Artigo ABS/HIPS blends obtained from WEEE: Influence of processing conditions and composition(2016) De Souza A.M.C.; Cucchiara M.G.; Ereio A.V.© 2016 Wiley Periodicals, Inc.The recycling of acrylonitrile-butadiene-styrene (ABS) and high-impact polystyrene (HIPS) from postconsumer electronic equipment housing was investigated. A preliminary study of shot size and particle size effects on the mechanical properties of ABS/HIPS (50/50) blends obtained directly via injection molding was conducted. Injection-molded specimens of ABS/HIPS blends, obtained at different compositions with or without previous extrusion, were subjected to mechanical, thermal, and morphological testing. Preliminary studies showed that a smaller particle size resulted in higher tensile and impact strength, regardless of the shot size used during injection molding. ABS/HIPS blends obtained using previous extrusion presented a slight increase in Young's modulus and a decrease in elongation at break and impact strength. The increase in glass-transition temperature related to the Polybutadiene (PB) phases of these blends indicated a possible increase in crosslinking structures during extrusion. In addition, these blends showed a coarse and heterogeneous morphology, suggesting that ABS did not completely mix with HIPS. Compared to processing conditions, the blend composition appeared to have a much stronger effect on the mechanical properties. The results obtained suggest the possibility of obtaining ABS/HIPS blends directly via injection molding as long as small ground particles are used.Artigo de evento Aisi 310 stainless steel formed by gelcasting: An alternative manufacturing method(2020-10-05) RODRIGUES, O. L. F.; NEVEZ, M. D. M.; F. S. Ortega© 2020 Trans Tech Publications Ltd, Switzerland.This work evaluates the microstructure and the yield strength under compression at room temperature and at 800°C of specimens prepared with AISI 310 stainless steel powder (D50 = 10 µm), manufactured by gelcasting. Parts were vacuum sintered in a single batch at 1280°C. At room temperature, specimens presented average yield strength of 270 MPa, and at 800°C, 105 MPa. Microstructure analysis involved the measurement of grain size along the vertical axis of cylindrical specimens, with special attention to the effect of particles settling, and was conducted using scanning electron and optical microscopy, and X-ray diffraction. Settling effect was assessed considering the position where the specimen was taken and was negligible: both density and yield strength did not vary significantly along the vertical axis.Artigo AISI 310 Stainless Steel Formed by Gelcasting: An Alternative Manufacturing Method(2020-10-05) OLIVEIRA, LOUISE FERNANDA RODRIGUES; NEVES, MAURÍCIO DAVID MARTINS DAS; F. S. OrtegaThis work evaluates the microstructure and the yield strength under compression at room temperature and at 800°C of specimens prepared with AISI 310 stainless steel powder (D50 = 10 μm), manufactured by gelcasting. Parts were vacuum sintered in a single batch at 1280°C. At room temperature, specimens presented average yield strength of 270 MPa, and at 800°C, 105 MPa. Microstructure analysis involved the measurement of grain size along the vertical axis of cylindrical specimens, with special attention to the effect of particles settling, and was conducted using scanning electron and optical microscopy, and X-ray diffraction. Settling effect was assessed considering the position where the specimen was taken and was negligible: both density and yield strength did not vary significantly along the vertical axis.Artigo de evento Alumina foam coated with strontium oxide as a heterogeneous catalyst(2012) Bassetti F.B.; Innocentini M.D.M.; Pereira G.J.; Ortega F.S.The most common method to produce biodiesel is the transesterification of oils in the presence of methanol and a catalyst. Catalysts may be either homogeneous or heterogeneous, whereas the heterogeneous consume fewer resources, energy and are reusable, being considered an environmentally attractive approach. This research presents the production of a heterogeneous catalysis system for biodiesel synthesis, consisting of alumina foam with a thin coating of SrO. The support, obtained by direct foaming of suspensions, presented approximately 90% vol. of highly connected pores. The SrO film was obtained by soaking the ceramic foam into either a Pechini resin with SrO precursors or an aqueous solution of strontium nitrate, followed by heating to 1400°C for 2 hours. The density and permeability of samples were evaluated and microstructure was characterized by EDS and SEM. The results show that the use of ceramic foams as catalyst support is feasible using the proposed route. © (2012) Trans Tech Publications, Switzerland.Artigo An investigation on recycled PET/PP and recycled PET/PP-EP compatibilized blends: Rheological, morphological, and mechanical properties(2015) De Souza A.M.C.; Caldeira C.B.© 2015 Wiley Periodicals, Inc.The effectiveness of P(E-co-MA-co-GMA) as a compatibilizer for recycled PET/PP and recycled PET/PP-EP (polypropylene (ethylene-propylene) heterophase copolymer) blends was investigated by means of morphological (scanning electron microscopy), rheological (small amplitude oscillatory shear), mechanical (tensile, flexural and impact tests), and thermal (differential scanning calorimetry) properties. Compatibilizer concentration ranged from 1 to 5 wt % with respect to the whole blend. All blends were obtained in a 90/10 composition using a twin screw extruder. Compatibilization effects for PETr/PP-EP were more pronounced due to ethylene segments present in both PP-EP and P(E-co-EA-co-GMA). PETr/PP-EP has shown greater dispersed phase size reduction, a more solid-like complex viscosity behavior and larger storage modulus at low frequencies in relation to PETr/PP blend. For both investigated blends, mechanical properties indicated an improvement in both elongation at break and impact strength with increasing compatibilizer content. PETr/PP-EP blends showed improved performance for the same level of compatibilizer content.Artigo ANÁLISE NUMÉRICA DE DELAMINAÇÃO EM MATERIAIS COMPÓSITOS CARBONO-EPÓXI(2013) SALERNO, GIGLIOLAArtigo Assessment of the utilization of different peroxide dispersion media on the controlled degradation of polypropylene(2013-01-05) MUNOZ, P. A. R.; BETTINI, S. H. P.A two-step investigation of polypropylene-controlled degradation was performed. First the controlled degradation of polypropylene was investigated by assessing the effects of using dicumyl peroxide (DCP) and 2,5-dimethyl-2,5- di(t-butylperoxy) hexane (DHBP) in different suspensions (neat, calcium carbonate, and organically modified montmorillonite). The second part of this research was performed according to a factorial design at two levels (2 2 experimental design) with center point, in which peroxide concentration and reaction time were studied. Polypropylene degradation was assessed by melt flow rate (MFR) and parallel plate rheometry. Results showed that DCP presented higher molar efficiency in polypropylene degradation reactions in relation to DHBP; likely due to radical recombination reactions. The results also indicate that clay may catalyze the recombination reactions of polypropylene radicals. Copyright © 2012 Wiley Periodicals, Inc.Artigo Assessment of the Von Mises Stresses and Stress Triaxiality in Notches Using Modified Tensile Specimens(2023-05-26) PEREIRA, L. DOS S.; Gustavo Donato; MATTAR NETO, M.© 2023 Universidade Federal de Sao Carlos. All rights reserved.Complete understanding of the local stress triaxiality and stress concentration is essential to ensuring structural safety of several structures. A combination of mechanical tests with numerical simulations can be used to obtain this information. One way to study stress triaxiality is by modifying the standard tensile test geometry (ASTM E8) with a notch. Based on previous results from the literature, five notches were chosen: 10, 5, 3, 2, and 1 mm. These geometries were tested, and the results were numerically reproduced using the Abaqus/Explicit 2020 software. The models used were a non-linear model with the Gurson-Tvergaard-Needleman damage model to reproduce the failure. The numerical analyses allowed the assessment of the von Mises stress and stress triaxiality near the notch to compare with the standard smooth specimen. Two instants were considered as crack propagation onset; the instant of the maximum von Mises stress in the element at the center of the specimen, where the failure process begins; and the moment of maximum stress in the true stress x true strain curve. For the von Mises stress analysis, the difference between the curves was small. The stress triaxiality is a better variable to visualize the influences of the notch. When the strain is equal to a 0.07 (instant of the maximum force for the standard specimens), for the smaller notches (1 and 2 mm), there is a region where the effective plastic strain is zero. Consequently, the stress triaxiality is larger in this region than in the center. For the crack propagation onset instant, the plastic strain occurs along the whole transversal section. In this instant, the maximum value of stress triaxiality occurs in the center for all specimens. These results demonstrate that the stress triaxiality changes as the strain increases, i.e., varies with time.Artigo CARACTERIZAÇÃO EXPERIMENTAL DO PROCESSO DE DELAMINAÇÃO EM MATERIAL COMPÓSITO DE FIBRA DE CARBONO E RESINA EPÓXI(2015) Amanda Coutinho Campanatti; SALERNO, GigliolaArtigo Characterization of heterogeneities in grain size by network analysis(2017) DUTRA, J. C.; Oliveira, T.E.Artigo Comparison between stainless steels and Nickel alloys through pitting corrosion resistance electrochemical tests(2021-04-27) FRAZÃO, I.; Rodrigo Magnabosco; DELBLANC, A.© 2021 Universidade Federal de Sao Carlos. All rights reserved.Critical pitting temperature (CPT) is one of the most accepted criteria for alloy classification concerning pitting corrosion. The techniques used nowadays to determine CPT have different parameters for alloys of different material classes, preventing the comparison between stainless steels and nickel based alloys. This study aims to compare the corrosion resistance of nickel based alloys and stainless steels with high corrosion resistance through potentiostatic tests for CPT determination, using a 3M MgCl2 aqueous solution. CPT values were effectively determined for the stainless steels studied but the technique did not have the same efficiency for nickel based alloys due to the occurrence of crevice corrosion, even considering the higher PRE of nickel based alloys.Artigo Correlating different techniques in the thermooxidative degradation monitoring of high-density polyethylene containing pro-degradant and antioxidants(2018) Antunes M.C.; Agnelli J.A.M.; Babetto A.S.; Bonse B.C.; Bettini S.H.P.© 2018 Elsevier LtdDifferent techniques were used to assess the effect of a primary and a secondary antioxidant, separately, and in combination with a pro-degradant (manganese stearate) on the thermooxidative abiotic degradation of high-density polyethylene (HDPE). The parameters measured over time at three temperatures (60, 70 and 80 °C) were variation in carbonyl index (CI), by means of infrared spectroscopy; reduction in tensile strain at break, by means of mechanical testing; reduction in molar mass distribution by means of size exclusion chromatography (SEC). Regardless of the presence of primary or secondary antioxidants, the same levels of degradation were attained. However, contrary to the secondary antioxidant, the primary antioxidant significantly increased induction time of HDPE oxidative degradation processes, evidenced by the shift in the “CI versus time” curve and by the considerably longer time for the strain at break to reach minimal values. Increase in thermooxidation temperature reduced induction time significantly.Artigo CORROSÃO POR PITE EM CONDIÇÃO EROSIVA DA LIGA Cu10Ni-3Al-1,3Fe ENVELHECIDA A 550°C, EM MEIO CONTENDO SULFATO(2012) LIBERTO, RODRIGO NASCIMENTO; Magnabosco, Rodrigo; ALONSO-FALLEIROS, NeusaArtigo Corrosion versus mechanical tests for indirect detection of alpha prime phase in UNS S32520 super duplex stainless steel(2011-04-05) FONTE, T. F.; Rodrigo Magnabosco; TERADA, M.; PADILHA, A. M.; COSTA, I.Alpha prime formation leads to material embrittlement and deterioration of corrosion resistance. In the present study, the mechanical and corrosion behavior of super duplex stainless steel UNS S32520 aged at 475°C from 0.5 h to 1,032 h was evaluated using microhardness measurements, Charpy impact tests, electrochemical impedance spectroscopy, and cyclic polarization curves. The sensibility of these tests to the effects of alpha prime phase was investigated. The microhardness test showed a gradual increase in hardness with aging time, whereas the impact tests revealed losses of about 80% in the energy absorption capacity for the material aged for 12 hin comparison with the solution-annealed samples. The most responsive analysis was the impact test, which indirectly revealed the presence of this deleterious phase in samples aged for 0.5 h. The electrochemical impedance spectroscopy and polarization tests were not highly sensitive to the alpha prime phase unless these are present In large amounts in the stainless steel. © 2011, NACE International.Artigo Corrosion Versus Mechanical Tests for Indirect Detection of Alpha Prime Phase in UNS S32520 Super Duplex Stainless Steel(2011) FONTES, Talita Filier; COSTA, I.;Costa, I.;Costa, Isolda;Costa, I;I. Costa;I Costa; MAGNABOSCO, R.; MAGNABOSCO, R.; TERADA, M.; PADILHA, A. F.Artigo de evento Cross-linked polyethylene (XLPE) as filler in high-density polyethylene: Effect of content and particle size(2019-01-22) FREITAS, R. S.; Bonse B.C.© 2019 Author(s).Cross-linked polyethylene (XLPE) scrap from electrical wire and cables was micronized and separated in average particle sizes of 100, 500 and 900 micrometer, after which sheets of XLPE concentrates in high-density polyethylene HDPE were produced, using a calendaring process. The sheets were ground and incorporated into HDPE by means of a twin-screw co-rotating extruder and subsequently injection molded into test specimens. A 2 by 2 factorial design with center point was used, where XLPE contents varied between 1 and 9 wt% and average particle size between 100 and 900 micrometers were assessed as to the effect of XLPE content and particle size on HDPE mechanical properties. Increase in XLPE content significantly increased only impact strength, and decreased tensile and flexural strength, and flexural modulus. The effect on tensile modulus and strain at break was not significant for the adopted 95% confidence interval. The increase in XLPE average particle size affected positively only impact strength of the material, and decreased strain at break and flexural modulus. The effect on tensile and flexural strength and on tensile modulus was not significant for the adopted 95% confidence interval. The interaction between the two variables decreased impact strength and increased tensile modulus, and was not significant for the other investigated properties.Artigo Direct measurement of interface energies of magnesium aluminate spinel and a brief sintering analysis(2017) Pereira G.J.; Bolis K.; Muche D.N.F.; Gouvea D.; Castro R.H.R.© 2017Surface and grain boundary energies are key parameters for understanding and controlling microstructural evolution. However, reliable thermodynamic data on interfaces of ceramics are relatively scarce, limiting the realization of their relevance in processes such as sintering and grain growth. In this work, the heat of sintering itself was used to quantify both surface and grain boundary energies in MgAl2O4 spinel. Nanoparticles were compacted and heated inside a Differential Scanning Calorimeter (DSC) when densification and grain growth were observed. The evolved heat signal was quantitatively attributed to the respective microstructural evolution in terms of interfacial area change, allowing determination of average surface and grain boundary energies for MgAl2O4 as 1.49 J m−2 and 0.57 J m−2, respectively. The data was then used to interpret the thermodynamics involved in density and grain growth during isothermal sintering of MgAl2O4.