RENE RAMOS DE OLIVEIRA

RENE RAMOS DE OLIVEIRA

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Graphene oxide nanosheets as fillers for thermoplastic-matrix nanocomposites
2020 - MOURA, E.A.; SANTOS, B.S.; ISHIKAWA, O.; SANTANA, J.G.; BARTOLOMEI, M.R.; OLIVEIRA, R.R.
Recent studies have shown that the synthesis of graphene oxide (GO) by chemical oxidation of graphite followed by its reduction is one's the most promising routes to prepare remarkable polymer/graphene nanocomposite materials with significant improvement of properties compared to the base polymer. The addition of a very small amount of reduced graphene oxide (RGO)in a polymer can enhance its properties, with respect to electrical conductivity, barrier resistance, stiffness, abrasion resistance, mechanical resistance, and fire retardancy. Numerous approaches have been established to prepare RGO from the desoxygenation of GO. This work presents the synthesis of graphene oxide by chemical oxidation of graphite followed by its photoreduction in aqueous dispersion using UV radiation and highlights some examples of RGO/thermoplastic-matrix nanocomposites prepared by melt processing. To evaluate the potential application of thermoplastic composites prepared, the RGO's content on the morphological, mechanical and thermal properties of the as-obtained nanocomposites has been assessed. In addition, GO/RGO nanosheets were characterized by ATR–FTIR, XRD, Raman, and FE-SEM. According to the results, it can be inferred that the addition of RGO leads to a remarkable improvement in the performance of thermoplastic-matrix nanocomposites and offers a competitive solution for various potential applications.
Development of biocomposite materials from biodegradable polymer and bio-hydroxyapatite derived from eggshells for biomedical applications
2019 - REIS, PEDRO R.S.; SANTANA, JULYANA G.; OLIVEIRA, RENE R.; RANGARI, VIJAYA K.; LOURENÇO, FELIPE R.; MOURA, ESPERIDIANA A.B.
Nowadays, significant advances have been made in the development of biodegradable polymeric materials for biomedical applications. This study aims to prepare and characterize composite materials based on PLA/PBAT, a biodegradable polymer blend, reinforced with bio-hydroxyapatite (bio-HAp). First, bio-HAp was obtained from eggshell residues by the wet precipitation method. PLA/PBAT blend with 1.5 wt% of bio-HAp was prepared by melt extrusion and injection molding process. Part of composite samples was irradiated with gamma radiation dose of 25 kGy, at room temperature and presence of air. The effects of the bio-HAp addition into the biodegradable blend were investigated by mechanical tests, XRD, DSC, FESEM, and cytotoxicity “in vitro” analysis and the correlation between the properties was discussed. In addition, the microbiological tests were carried out at irradiated and non-irradiated composite samples in order to evaluate the efficiency of the radiation dose of 25 kGy at composite materials sterilization.
Mechanical, thermal, morphology and barrier properties of flexible film based on polyethylene-ethylene vinyl alcohol blend reinforced with graphene oxide
2017 - SANTANA, JULYANA G.; ORTIZ, ANGEL; OLIVEIRA, RENE R.; RANGARI, VIJAY K.; GUVEN, OLGUN; MOURA, ESPERIDIANA A.B.
Ethylene-vinyl alcohol (EVOH) copolymers are widely used in the food packaging industry as gas barrier properties to oxygen, organic solvents, and food aromas. EVOH is very sensitive to moisture and its gas barrier ability deteriorates in high relative humidity conditions. This work aims to prepare flexible films based on melt-blending high density polyethylene (HDPE) and ethylene-vinyl alcohol (HDPE/EVOH/EVA blend) reinforced with graphene oxide (GO). The HDPE/EVOH/EVA/GO flexible films were prepared by twin-screw extrusion and blown film extrusion processing. The flexible films samples were characterized by tensile tests, TG, DSC and FE-SEM analysis and the correlation between properties was discussed. In addition, the oxygen permeability tests were performed at 23 °C, 0 and 90% relative humidity using an OX-TRAN (MOCON Inc.).
Biodegradable polymer blends reinforced with bio-hydroxyapatite nanoparticle - preparation and characterization
2017 - REIS, PEDRO R.S.; SANTANA, JULYANA G.; OLIVEIRA, RENE R.; RANGARI, VIJAYA K.; MOURA, ESPERIDIANA A.B.
Nowadays significant advances have been made in the development of biodegradable polymeric materials for biomedical applications. The purpose of this study was to preparation and characterization of biodegradable polymer blend reinforced with bio-hydroxyapatite nanoparticle from eggshell by sonochemical method. Biodegradable polymer blends based on PLA (Poly(lactic acid)) and the PBAT (butylene adipate-co-terepthalate)) reinforced with 1-5 wt. % of bio-hydroxyapatite were prepared by melt extrusion, using a twin screw extruder and injection molding machine to obtain specimen test. The effects of the bio-hydroxyapatite addition on properties of PLA/PBAT biodegradable blend were investigated by tensile tests, XRD, DSC, TG and SEM-FEG analysis and the correlation between the results was discussed.