ANGEL VISENTIM ORTIZ
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Capítulo IPEN-doc 25004 Mechanical, thermal, morphology and barrier properties of flexible film based on polyethylene-ethylene vinyl alcohol blend reinforced with graphene oxide2017 - 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.).Resumo IPEN-doc 23584 Mechanical, thermal and barrier properties of EVOH/GRAPHENE oxide flexible films treated by electron beam radiation2016 - SANTANA, JULYANA G.; ORTIZ, ANGEL; AKBULUT, MESHUDE; RANGARI, VIJAY K.; VALENZUELA-DIAZ, FRANCISCO; GUVEN, OLGUN; MOURA, ESPERIDIANA A.B.Ethylene vinyl alcohol (EVOH) copolymers are semicrystalline random copolymers of ethylene and vinyl alcohol that are widely used in the food packaging industry owing to their excellent chemical resistance, high transparency as well as excellent gas barrier properties to oxygen, organic solvents, and food aromas. However, EVOH is very sensitive to moisture and its gas barrier ability deteriorates in high relative humidity conditions. This study presents the preparation of EVOH/Graphene oxide films by twin-screw extrusion and blown film extrusion processing. The preparation of EVOH/Graphene oxide (EVOH/GO) films was carried out in two steps: EVOH with Graphene oxide powder (0-0.5 wt. %) was fed into a co-rotating twin-screw extruder, then the EVOH/GO nanocomposite was transformed into thin films using an extrusion blown film, single screw machine with 25 mm diameter and specimens test samples were obtained. Part of EVOH/GO flexible films were submitted to electron-beam irradiation at 150 and 200 kGy, using a 1.5 MeV electron beam accelerator, at room temperature in presence of air. The irradiated and non-irradiated samples were characterized by mechanical tests, XRD, TG, DSC, FE-SEM and TEM 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.). The free volume hole radius of both crystalline (0.201 nm) and amorphous parts (0.258 nm) of EVOH only and EVOH-GO samples were measured by Positron Annihilation Life-Time Spectroscopy. According to the results of the optical transparency measured, the EVOH/GO retaining good transparency films for all graphene oxide percentage added. The EVOH matrix with 0.1-0.4 wt. % graphene oxide content presented better oxygen barrier properties at 0 % relative humidity when compared with neat EVOH flexible films. After irradiation treatment, both, mechanical and oxygen barrier properties were drastically improved. Upon introduction of GO into EVOH matrix a reduction in the free volume hole radius in both parts have been observed indicating the formation of a more compact structure in EVOH/GO nanocomposites. Formation of hydrogen bonding between OH groups of EVOH and polar groups on graphene is assumed to be responsible for the reduction in free volume.Artigo IPEN-doc 22626 Morphology, optical transparency and oxygen barrier of EVOH/graphene oxide films2016 - ORTIZ, ANGEL; AKBULUT, MESHUDE; SANTANA, JULYANA G.; RANGARI, VIJAY K.; VALENZUELA-DIAZ, FRANCISCO; GUVEN, OLGUN; MOURA, ESPERIDIANAFood packaging materials require high gas and moisture barrier in other to preserve the quality of the products during storage and handling. Polyolefin materials have been widely used due to their water vapor resistance. Ethylene–vinyl alcohol copolymer (EVOH) is used as a gas barrier layer in packaging products that require high gas barrier. However, EVOH is very sensitive to moisture and its gas barrier ability deteriorates in high relative humidity conditions. In order to overcome the adverse effects of moisture on EVOH film this paper studies the incorporation of small amount of graphene oxide in EVOH by melt processing and evaluates their effects on morphology, optical transparency and oxygen barrier of EVOH film. The EVOH/Graphene oxide (EVOH/GO) film were processed by twin-screw extrusion and extrusion blown film processing. The films was characterized by XRD, FEG-SEM, and UV/VIS analysis. In addition, the oxygen transmission rate (OTR) were performed at 23 C, 0 % and 90 % relative humidity using an OX-TRAN (MOCON Inc.). According to the results of the optical transparency measured, the EVOH/GO retaining good transparency films for all graphene oxide percentage added. The graphene oxide at only 0.1 wt. % into the EVOH matrix drastically improved the oxygen barrier properties of EVOH/GO flexible film in both, 0 % and 90 % of the relative humidity test conditions.