Avaliação da orientação molecular de moldados de polipropileno utilizando figuras de pólo obtidas por difração de raios X

Almeida, Álvaro M.; Branciforti, Márcia Cristina; Bretas, Rosário Elida Suman

doi:10.1590/s0104-14282007000100009

Cited by 6 publications

(13 citation statements)

References 26 publications

(76 reference statements)

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“…As the flow rate increased, the flow velocities increased increasing the distinctive molecular orientation of PP. These results agree with earlier results 22 .…”

Section: Influence Of the Injection Flow Ratesupporting

confidence: 94%

“…The formation of the β-phase, among other factors, is dependent of the shear level imposed to the polymer during the injection molding; it is known 1,22 that its amount decreases with the decrease in shear rate, as confirmed by our results. Table 5 shows the measured intensities of the (300) peak at all studied conditions.…”

Section: Crystalline Phase Analysessupporting

confidence: 86%

“…The maximum orientation value is usually obtained in the transition zone, being almost zero in the center of the molded sample, as a result of the shear rates, which are maximum near the wall and zero in the center. This molecular orientation gradient is responsible for the improved properties in the orientation direction; on the other hand, the properties along the perpendicular direction usually are worse [22][23][24][25] . The parameters that affect the molecular orientation are: shear and elongation tensions imposed to the molten polymer during their solidification, processing conditions (injection and mold temperatures, packing pressure and flow rate, among others) and intrinsic characteristics of the polymer (relaxation time, crystallization kinetics and chains rigidity, for example [22][23][24][25][26][27][28][29][30][31][32][33] ).…”

Section: Introductionmentioning

confidence: 99%

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A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

2009

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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 between the processing conditions, phase contents and PP α-phase molecular orientation of injection molded PP resins. In both resins, it was observed that the α-phase was present in all regions along the thickness while the β-phase was present mainly in the external layers, decreasing from the surface to the core; however this last phase was present in a very small amount in the NPP resin. For both polymers, the orientation of the macromolecules c-axis was higher along the flow direction (RD) than along the transverse direction (TD). The b-axis of the PP α-phase molecules was oriented to the thickness direction (ND). The orientation of the c-axis along RD and b-axis along ND of the NPP samples was considerably higher than of the HPP samples, due to the NPP faster crystallization kinetics. For both polymers, the most influential processing parameters on the molecular orientation were the mold temperature and flow rate. The results indicate that, as the mold temperature increased, the characteristic molecular orientation of PP α-phase, with c-axis along RD and b-axis along ND, decreased. With increase in the flow rate an increase of the c-axis molecular orientation of the samples along RD was observed.

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“…As the flow rate increased, the flow velocities increased increasing the distinctive molecular orientation of PP. These results agree with earlier results 22 .…”

Section: Influence Of the Injection Flow Ratesupporting

confidence: 94%

Section: Crystalline Phase Analysessupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

2009

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“…A fratura foi realizada no sentido transversal da amostra, contudo é difícil assegurar que a fratura tenha ocorrido exatamente a 90° do sentido longitudinal da amostra, o que pode explicar as diferenças de rugosidades observadas. Durante a extrusão é possível que ocorra orientação de estruturas que levem à cristalização preferencial em um determinado sentido do material processado [30,31] . Durante o processamento, observou-se claramente a progressiva diminuição da viscosidade do extrudado em função do aumento do teor de ácido cítrico, bem como um aumento da característica adesiva das amostras, o que já foi relatado anteriormente para TPS processados na presença de ácidos orgânicos [28] .…”

Section: Obtenção Do Amido Termoplástico Modificado Pelo Processamentunclassified

Blendas compatíveis de amido termoplástico e polietileno de baixa densidade compatibilizadas com ácido cítrico

Miranda

Carvalho

2011

Polímeros

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Resumo: Blendas de polietileno de baixa densidade (PEBD) e amido termoplástico (TPS) modificado foram preparadas via extrusão reativa (REX) e caracterizadas por microscopia eletrônica de varredura (MEV), espectroscopia na região do infravermelho com transformada de Fourier (FTIR), absorção de umidade em ambiente com 53% de umidade relativa e difração de raios-X. Em uma primeira etapa, foi preparado o TPS-modificado, via REX a partir de uma mistura de amido de milho, ácido cítrico e glicerol. As blendas TPS-PEBD foram preparadas pelo processamento de uma mistura do TPS modificado e PEBD, ambos em peletes, em uma extrusora de rosca simples. Foi observado um significativo efeito de compatibilização, atribuído especialmente à redução da viscosidade da fase TPS e consequente redução da tensão interfacial entre as fases de TPS e PEBD. Os espectros de FTIR apresentaram deslocamentos de bandas de absorção do amido confirmando o efeito de compatibilização pelo ácido cítrico. Observou-se também significativa alteração da morfologia das blendas, especialmente para as blendas preparadas com adição de 1,0 -1,5 % de ácido cítrico, que apresentaram estrutura da fase dispersa mais fina e homogênea. Palavras-chave: Amido termoplástico, blendas biodegradáveis, polietileno, extrusão reativa, compatibilização. Compatible Blends of Thermoplastic Starch and Low Density Polyethylene Compatibilized with Citric AcidAbstract: Blends of citric acid-modified thermoplastic starch (TPS) and low density polyethylene (LDPE) were prepared by reactive extrusion (REX) and characterized by scanning electron microscopy (SEM) of the fragile fracture surfaces, Fourier-transform infrared spectroscopy (FTIR), water absorption in 53% relative humidity environment and by X-ray diffraction. The modified TPS was prepared by the reactive extrusion of a mixture of corn starch, citric acid and glycerol (30%). TPS-LDPE blends were then prepared by the processing of TPS and PEBD both in pellets in a single screw extruder. It was observed an important compatibilization effect, attributed to the reduction of TPS melt viscosity and consequently the reduction of the interfacial tension between TPS and PEBD phases. The FTIR spectra showed shifting of starch bands confirming the compatibilization effect of citric acid. Important change on blend morphology as function of the TPS modification were observed, in particular for the blends prepared with the addition of 1,0 -1,5% AC which showed a more homogeneous and finer dispersed phase. Keywords: Thermoplastic starch, biodegradable blends, polyethylene, reactive extrusion, compatibilization. IntroduçãoO desenvolvimento de novos materiais poliméricos derivados de fontes renováveis tem motivado um grande número de estudos recentemente. O amido é um dos materiais mais promissores para essa finalidade, pois é produzido em grandes quantidades em praticamente todas as regiões do mundo, tem baixo custo e pode ser utilizado tanto na produção de insumos químicos básicos como diretamente na composição de polímeros termoplásticos ...

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“…PP H103 and H503 from Braskem. PP H103 with density 0.905 g/cm 3 , Melting Flow Index (MFI) = 40 g/10 min (230°C/2.16 kg), with average molecular weight (M w ) 235.597 g/mol 27 and PP H503 with density 0.905 g/cm 3 , MFI = 3.5 g/10 min (230°C/2.16 kg), with M w 470.000 g/mol 28 . Jatobá WP, that is, Hymenaea courbaril , used as filler was supplied by a local company (Campina Grande ‐ PB).…”

Section: Experimental Materialsmentioning

confidence: 99%

Polypropylene/wood powder/ethylene propylene diene monomer rubber‐maleic anhydride composites: Effect of PP melt flow index on the thermal, mechanical, thermomechanical, water absorption, and morphological parameters

et al. 2020

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Environmental damage promoted trough post‐consumer waste from the wood industry has worried the society, while its inadequate disposal has raised concerns of the scientific community. Environmentally and economically effective alternative is reusing this residue to produce smart composites. Therefore, this work aimed to investigate the performance of polypropylene (PP)/Jatobá Wood Powder (WP) composites compatibilized with ethylene propylene diene monomer rubber‐maleic anhydride (EPDM‐MA). The effect of distinct melt flow index (MFI) (PP H103 and PP H503) was also investigated. The composites were characterized using differential scanning calorimetry, thermogravimetry, mechanical properties (tensile, flexural, impact, and Shore D hardness), heat deflection temperature, Vicat softening temperature, water absorption and scanning electron microscopy (SEM). Addition of EPDM‐MA, increased impact strength. The best performance was observed for the composition with 10% EPDM‐MA and PP with lower MFI (PP H503). EPDM‐MA also decreased the water absorption for both PP, most due to the chemical interactions among composite phases. SEM images suggest encapsulation of wood particles by EPDM‐MA, promoting better composites performance. Reported results are valuable for the recycling industry, as well as are economically and environmentally promising.

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Avaliação da orientação molecular de moldados de polipropileno utilizando figuras de pólo obtidas por difração de raios X

Cited by 6 publications

References 26 publications

A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

Blendas compatíveis de amido termoplástico e polietileno de baixa densidade compatibilizadas com ácido cítrico

Polypropylene/wood powder/ethylene propylene diene monomer rubber‐maleic anhydride composites: Effect of PP melt flow index on the thermal, mechanical, thermomechanical, water absorption, and morphological parameters

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