Time filter

Source Type

Howarth J.L.,Instituto Superior Tupy | Pouzada A.S.,University of Minho | Maia J.M.,Case Western Reserve University | Salmoria G.V.,Federal University of Santa Catarina | Ahrens C.H.,Federal University of Santa Catarina
Journal of Composite Materials | Year: 2014

Composites based on metallic fibers and thermosetting polymers are being increasingly used for molding blocks of hybrid injection molds, thereby improving the mechanical and thermal properties. However, an adequate study on the behavior of steel fibers in a reactive epoxy resin is necessary to understand how to maintain suitable mold properties. In this paper, the sedimentation velocity of short steel fiber suspensions in reactive epoxy resin was estimated using a model emerging from the Stokes equation and considering the resin rheology and correction factors for the fiber shape and concentration. DMP (2,4,6-tris (dimethylamino-methyl) phenol) was the accelerator more suitable for this type of composites because it increases the rate of cure and reduces the gel time more pronouncedly than any of the other common accelerators. Samples were manufactured with epoxy resin, short steel fiber and DMP as accelerator, and using anti-sedimentation equipment. The distribution of the fibers was observed in all composites. The viscosity data were used to predict the time in the anti-sedimentation equipment necessary to reach a minimum sedimentation velocity using the mathematical model. Results showed that this velocity is recommended to be below 3.28×10-8 m/s to avoid sedimentation of the steel fibers. © 2013 The Author(s).

Bond D.,Instituto Superior Tupy | Becker S.F.,Federal University of Santa Catarina | D'Oliveira A.S.C.M.,Federal University of Paraná
Soldagem e Inspecao | Year: 2011

Welded coatings can be use to enhance the service life of components that operate under severe conditions. Plasma Transferred arc (PTA) is a hardfacing process, recognized for its homogeneous high quality deposits produced, and uses atomized feedstock. The bond of materials with different chemical compositions is always a challenge. This bond will depend on the optimization of the processing parameters, which influences the microstructure of the coatings and consequently its performance. This work analyzed the role of feedstock powder grain size, deposition current and mode on the hardness of a Co based alloy (Stellite 6) coating using a experiment design tool. The results showed that the powder grain size of the feedstock has to be considered as a processing parameter together with the deposition current and mode as it influenced coating hardness.

Zacharuk M.,Instituto Superior Tupy | Becker D.,Instituto Superior Tupy | Coelho L.A.F.,Santa Catarina State University | Pezzin S.H.,Santa Catarina State University
Polimeros | Year: 2011

In this work the reaction of polyethylene glycol (PEG) and epoxy resin (BADGE) in the presence of N,N-dimethylbenzylamine (DMBA) was studied. The reaction products were evaluated by infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and viscosity measurements. Samples cured with a polyamine-based hardener were also submitted to tensile tests and differential scanning calorimetry (DSC). The results of the viscosity analyses, FTIR and RMN (1H) confirmed the reaction between DGEBA epoxy groups and PEG hydroxyl groups in the presence of DMBA, at 100 °C. DSC analyses and tensile tests of cured systems showed that the reaction of DGEBA with PEG leads to a reduction of Tg, generating a more flexible material.

Hupalo M.F.,State University of Ponta Grossa | Martins F.G.,Instituto Superior Tupy | Ramos D.S.,Instituto Superior Tupy | Warmling G.,Instituto Superior Tupy
Revista Materia | Year: 2010

Metallurgic industry has sought for more efficient casting processes. Fuel oil and gas-fired rotary furnaces rise as an interesting alternative for cast irons production. It must be emphasized that during the fusion process in rotary furnaces, a higher burning of alloying elements occur, demanding the use of a suitable carbonizing technique in order to attend the chemical composition specifications. The present work aimed in the application and study of different carbonizing techniques during the production of gray and ductile cast irons using fuel oil and gas-fired rotary furnaces. Two carburant types with different particle sizes were added in different stages of fusion process. Results show that carbonizing efficiency is strongly affected by the state of the metallic charge. The best results were obtained by the calcined petroleum coke with a particle size of 1-3 mm, added to the pasty metal loading.

The procedure for obtaining nanocomposite by dispersing the nanoparticles in matrix polymer in solution with subsequent elimination of the solvent has been widely used, considering better efficiency in obtaining homogeneity of the final product. However, the presence of residual solvent may affect the nanocomposites in micro-and macroscopic properties of the product. The aim of this study was to evaluate the thermal properties of nanocomposites of poly(vinyl chloride)/multi-walled carbon nanotube obtained from the polymer solution and dispersion of carbon nanotubes in tetrahydrofuran (THF), as well as the electrical resistivity of nanocomposites and the influence of residual solvent. The presence of residual tetrahydrofuran reduces the glass transition temperature (Tg) up to 26°C, being independent of the amount of carbon nanotubes. The total elimination of the solvent is an important factor that does not induce changes in the properties of the polymeric matrix. The graft-COOH groups in the structure of the nanotubes leads to a considerable reduction of the electrical resistivity in ten orders of magnitude, from 0.4 %wt of nanotubes in the nanocomposite composition.

Loading Instituto Superior Tupy collaborators
Loading Instituto Superior Tupy collaborators