Marcio Oliveira - Academia.edu (original) (raw)
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Universidade Federal de Santa Catarina - UFSC (Federal University of Santa Catarina)
Universidade Estadual Paulista "Júlio de Mesquita Filho"
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Papers by Marcio Oliveira
Polymer Engineering and Science, 1996
A theoretical basis for the prediction of the properties of mixtures of virgin and reprocessed po... more A theoretical basis for the prediction of the properties of mixtures of virgin and reprocessed polymers is presented. The concept is developed using equations that describe the loss of polymer properties as a function of processing cycles. These equations correspond to properties that are important in characterization and quality control, such as melt flow index and tensile and impact strengths. Experimental data were determined and used to test the models derived. For glass-fiber-reinforced thermoplastics, the data on the degradation of fiber lengths and mechanical properties can help to understand the effect of reprocessing on the fiber-matrix interaction.
Materials Research Innovations, 2001
We apply a macromolecular-orientation approach to produce high molecular weight polyethylene (HMW... more We apply a macromolecular-orientation approach to produce high molecular weight polyethylene (HMWPE) + hydroxyapatite (HA) ductile composites with the stiffness and strength within the range of human cortical bone. Our composites are produced with different amounts (10 to 50% by weight) of the reinforcement by two procedures: bi-axial rotating drum and twin screw extrusion (TSE). The processing is by conventional injection molding and by Scorim (shear controlled orientation in injection molding) under a wide range of processing windows. Tensile testing is performed and the corresponding performance related to the morphology evaluated by polarized light microscopy and scanning electron microscopy. The control of the processing parameters led to significant improvements of the tensile properties. Compounding by TSE and then processing by Scorim produces the maximum modulus of 7.4 GPa and the ductility as high as 19%, for the HA weight fraction of 30%. These mechanical properties match those of bone, and were obtained with much smaller amounts of HA reinforcement then has been previously reported in literature. Our PE + HA composites present the additional benefit of being ductile even for 50% HA amounts. The use Scorim is a unique way of inducing anisotropy to thick sections and to produce very stiff composites that may be used in biomedical applications with important mechanical loads. This fact, combined with the bioactive behavior of the HA phase, makes our composite usable for orthopedic load-bearing implants.
O Atol das Rocas, que recentemente foi declarado pela UNESCO patrimônio natural da humanidade, é ... more O Atol das Rocas, que recentemente foi declarado pela UNESCO patrimônio natural da humanidade, é o único do Atlântico Sul e dista 144 milhas náuticas (266,68 Km) da costa brasileira. A corrente predominante nesta localidade é a Sul Equatorial que se estende até a costa do Ceará e posteriormente da origem a corrente das Guianas. As condições oceanografias e estratégias reprodutivas das várias famílias de peixes associados aos recifes de Rocas e da Costa do Ceará podem influenciar na dispersão larval e, conseqüentemente, caracterizar a estruturação genética dessas populações. Foram analisadas geneticamente populações do Atol das Rocas e Costa do Ceará, de duas espécies de peixes recifais com desova pelágia e longo período de duração larval. São elas: Acanthurus chirurgus e Cephalopholis fulva. A metodologia utiliza foi eletroforese de isoenzimas. Para A. chirurgus os resultados indicaram a presença de estoques pesqueiros diferenciados entre as duas populações. O mesmo não foi encontrado para as populações de C. fulva que apresentaram fluxo gênico irrestrito. Palavras-chave: Acanthurus chirurgus, Cephalopholis fulva, disperção larval, fluxo gênico, isoenzimas, Atol das Rocas.
Polymer Engineering and Science, 1996
A theoretical basis for the prediction of the properties of mixtures of virgin and reprocessed po... more A theoretical basis for the prediction of the properties of mixtures of virgin and reprocessed polymers is presented. The concept is developed using equations that describe the loss of polymer properties as a function of processing cycles. These equations correspond to properties that are important in characterization and quality control, such as melt flow index and tensile and impact strengths. Experimental data were determined and used to test the models derived. For glass-fiber-reinforced thermoplastics, the data on the degradation of fiber lengths and mechanical properties can help to understand the effect of reprocessing on the fiber-matrix interaction.
Materials Research Innovations, 2001
We apply a macromolecular-orientation approach to produce high molecular weight polyethylene (HMW... more We apply a macromolecular-orientation approach to produce high molecular weight polyethylene (HMWPE) + hydroxyapatite (HA) ductile composites with the stiffness and strength within the range of human cortical bone. Our composites are produced with different amounts (10 to 50% by weight) of the reinforcement by two procedures: bi-axial rotating drum and twin screw extrusion (TSE). The processing is by conventional injection molding and by Scorim (shear controlled orientation in injection molding) under a wide range of processing windows. Tensile testing is performed and the corresponding performance related to the morphology evaluated by polarized light microscopy and scanning electron microscopy. The control of the processing parameters led to significant improvements of the tensile properties. Compounding by TSE and then processing by Scorim produces the maximum modulus of 7.4 GPa and the ductility as high as 19%, for the HA weight fraction of 30%. These mechanical properties match those of bone, and were obtained with much smaller amounts of HA reinforcement then has been previously reported in literature. Our PE + HA composites present the additional benefit of being ductile even for 50% HA amounts. The use Scorim is a unique way of inducing anisotropy to thick sections and to produce very stiff composites that may be used in biomedical applications with important mechanical loads. This fact, combined with the bioactive behavior of the HA phase, makes our composite usable for orthopedic load-bearing implants.
O Atol das Rocas, que recentemente foi declarado pela UNESCO patrimônio natural da humanidade, é ... more O Atol das Rocas, que recentemente foi declarado pela UNESCO patrimônio natural da humanidade, é o único do Atlântico Sul e dista 144 milhas náuticas (266,68 Km) da costa brasileira. A corrente predominante nesta localidade é a Sul Equatorial que se estende até a costa do Ceará e posteriormente da origem a corrente das Guianas. As condições oceanografias e estratégias reprodutivas das várias famílias de peixes associados aos recifes de Rocas e da Costa do Ceará podem influenciar na dispersão larval e, conseqüentemente, caracterizar a estruturação genética dessas populações. Foram analisadas geneticamente populações do Atol das Rocas e Costa do Ceará, de duas espécies de peixes recifais com desova pelágia e longo período de duração larval. São elas: Acanthurus chirurgus e Cephalopholis fulva. A metodologia utiliza foi eletroforese de isoenzimas. Para A. chirurgus os resultados indicaram a presença de estoques pesqueiros diferenciados entre as duas populações. O mesmo não foi encontrado para as populações de C. fulva que apresentaram fluxo gênico irrestrito. Palavras-chave: Acanthurus chirurgus, Cephalopholis fulva, disperção larval, fluxo gênico, isoenzimas, Atol das Rocas.