Isotactic Polypropylene
Mostrando 1-12 de 13 artigos, teses e dissertações.
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1. Molecular weight and tacticity effect on morphological and mechanical properties of Ziegler–Natta catalyzed isotactic polypropylenes
The morphological and mechanical properties of Ziegler–Natta catalyzed isotactic polypropylenes as influenced by the molecular weight and tacticity was investigated. Polypropylene samples were injection moulded into standard disks with a HAAKE MiniJet II injection moulder at 190 °C and 200 bar for morphological and mechanical tests. The morphological and
Polímeros. Publicado em: 04/12/2015
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2. High-speed camera analysis of rupture of polypropylene specimens in tensile tests / Análise das imagens de ruptura de corpos de prova de polipropileno em ensaio de tração obtidas através de câmera de alta velocidade
Injection-molded isotactic polypropylene, iPP, samples present different properties variation as a function of the injection parameters. One of these properties is the rupture propagation on the material, which was studied with the use a high-speed camera adjusted to capture from 18,000 to 45,000 frames per second. The injection molding parameters modified w
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 29/07/2011
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3. Microstructural orientation of isotactic polypropylene studied by computerized scanning eletron microscopy image analysis
We evaluate the orientation of microstructural elements of isotatic polypropylene (i-PP) before and after deformation using computerized “Quantikov” software analysis of Scanning Electron Microscopy (SEM) images. We observed that before deformation through uniaxial compression, the polymeric material doesn’t exhibit any significant orientation. After d
Publicado em: 2010
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4. A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins
The development of α and β-phases and the molecular orientation of injection molded disks of two isotactic polypropylene (i-PP) resins were studied by wide angle X-ray diffraction (WAXD) and pole figures. A nucleated (NPP) and non-nucleated (HPP) polymers were analyzed. The main proposal of this article was the comprehensive study of the interrelations bet
Materials Research. Publicado em: 2009
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5. Processamento reativo de nanocompósitos iPP-POSS
Os modos de interação de silsesquioxano poliédrico oligomérico (POSS) de gaiolas fechadas com distintos grupos funcionais foram avaliados na nanoestruturação de polipropileno isotático (iPP) via processamento reativo. Analisaram-se POSS com grupos substituintes isobutila, alila e vinila em concentrações de 0,5, 1, 2 e 5%m misturados a iPP fundido ut
Publicado em: 2009
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6. The role of defect microstructure in the crystallization behavior of metallocene and MgCl2-supported Ziegler-Natta isotactic poly(propylenes)
The intermolecular defect distribution of poly(propylenes) of the Ziegler-Natta (ZN) and metallocene (M) types is assessed by classical fractionation and analysis of the fractions by GPC and 13C NMR. In addition, the linear growth rates, a property sensitive to differences in defects distribution in the poly(propylene) chain, are used to infer the stereobloc
Polímeros. Publicado em: 2003-12
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7. Influence of the elastomeric polypropylene addition on the properties of commercial metallocenic polypropylene
Polypropylene with special properties can be obtained by metallocenic catalysts. These catalytic systems represent the beginning of a new age in polyolefins technology. In this work, the influence of the addition of a syndiotactic polypropylene (s-PP) on the processability and mechanical properties of a commercial isotactic polypropylene (i-PP) obtained by m
Materials Research. Publicado em: 2001-10
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8. Microstructural orientation of isotactic polypropylene studied by computerized scanning eletron microscopy image analysis
We evaluate the orientation of microstructural elements of isotatic polypropylene (i-PP) before and after deformation using computerized "Quantikov" software analysis of Scanning Electron Microscopy (SEM) images. We observed that before deformation through uniaxial compression, the polymeric material doesn’t exhibit any significant orientation. After defor
Materials Research. Publicado em: 2001
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9. New nuclear magnetic resonance methods for studying slow dynamics in organic solids: applications to polymers and proteins / Novas metodologias de ressonância magnética nuclear para o estudo da dinâmica lenta em materiais orgânicos no estado sólido: aplicações em polímeros e proteínas
Solid-State Exchange NMR is an important method to characterize details of dynamic process in materials science. However, the application of these techniques to study complex materials has been limited. In this work new solid-state Exchange NMR techniques, which allows efficient analysis of molecular motions in the millisecond time scale, are presented. The
Publicado em: 2001
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10. Tetracloreto de titanio suportado em dioxido de titanio quimicamente reduzido como catalisador de Ziegler-Natta
Titanium(IV) chloride (TiCI4) was heterogenized on titanium dioxide (TiO2 red) chemically reduced with n-butyllithium (n-BuLi). The so obtained Ziegler-Natta catalyst was used for propylene polymerization. Variation of the different parameters involved in the catalyst synthesis showed that the Ti(III) chloride concentration of the catalyst as well as the cat
Publicado em: 1995
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11. Estudo do efeito da radiação gama sobre as propriedades de blendas baseadas em polipropileno isotatico
Due to a large demand for adequate utilization of polymeric materials esterilized by gamma rays in medical applications, in this work we studied different formulations based on isotactic polypropylene (iPP) in order to analyse its behavior under radiation. The formulations were based on mixtures of isotactic polypropylene and atactic polypropylene (at-PP), a
Publicado em: 1992
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12. Foto-oxidação de polipropileno sob tensão mecanica
There are few works on polymer degradation caused by two or more initiation ways. There are some works on chemo-mechanical (ozone and load), in thermomechanical and very few works on photomechanical degradation. In this work we studied the photo-oxidation of isotactic polypropylene films under load. These films were low and highly oriented, and its formulati
Publicado em: 1991