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Master's Dissertation
DOI
10.11606/D.3.2007.tde-14012008-121630
Document
Author
Full name
Ana Maria Arteaga Vasquez
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2007
Supervisor
Committee
Demarquette, Nicole Raymonde (President)
Giudici, Reinaldo
Santos, Amilton Martins dos
Title in Portuguese
Estudo das propriedades reológicas de polipropilenos em fluxos de cisalhamento e fluxos elongacionais.
Keywords in Portuguese
Polímeros
Polipropileno
Reologia
Viscosidade
Abstract in Portuguese
Neste trabalho, métodos experimentais para estimar as viscosidades elongacional e de cisalhamento mediante um canal de contração abrupta foram desenvolvidos. Os dados reológicos em fluxos de cisalhamento foram comparados com os resultados mediante o reômetro rotacional e o reômetro capilar. Os resultados foram utilizados para avaliar a influência da estrutura molecular nas propriedades reológicas de vários polipropilenos com diferentes massas moleculares, distribuição de massas moleculares e teor de ramificações. Além disso, polipropilenos degradados termomecânicamente foram estudados. A massa molecular e a distribuição de massas moleculares foram obtidas através de Cromatografia de permeação em gel (GPC). Os resultados obtidos mostraram que a matriz elongacional é útil para simular processos de transformação, visto que podem ser alcançadas altas taxas de deformação, que dependem dos valores máximos dos parâmetros de processamento, os quais dependem dos limites máximos do equipamento utilizado. Os resultados em fluxos de cisalhamento avaliados mediante a matriz elongacional mostraram que possuem uma excelente concordância com os resultados obtidos por cisalhamento oscilatório de pequenas amplitudes (COPA) no reômetro rotacional. Os resultados em fluxos elongacionais mostraram que as medidas são muito sensíveis à estrutura molecular, principalmente à presença de ramificações longas, principalmente a baixas taxas de deformação. No caso do polipropileno degradado termomecânicamente, tanto sua massa molecular quanto as suas viscosidades elongacional e de cisalhamento diminuem devido à cisão de cadeias e, as medidas reológicas mostram-se mais sensíveis a essas mudanças do que as medidas de GPC.
Title in English
Study of rheological properties of polypropylenes in shear and elongational flows.
Keywords in English
Plymers
Polypropylene
Rheology
Viscosity
Abstract in English
In this work, experimental methods to evaluate elongational and shear viscosities using a planar channel with an abrupt contraction (also called Cogwell die) were developed. The shear viscosity measurements were compared to measurements obtained using a rotational rheometer and a capillary rheometer. The elongational die was used to evaluate the influence of the molecular weight, molecular weight distribution and chain structure on the rheological properties of polypropylene. The influence of thermomechanical degradation of PP on its rheological properties was also studied. The molar mass and molar mass distribution were evaluated using GPC. It was found that the planar channel can be used successfully to evaluate the elongational viscosity at rates that correspond to polymer processing conditions. The shear viscosity measurements obtained using the planar die were in good agreement with measurements obtained by small amplitude oscillatory shear (SAOS). The elongational viscosity was sensitive to molecular structure, essentially at low deformations. It was also shown that the molar mass, molar mass distribution and amount of branching affects the shear viscosity and that rheological measurements may be more sensitive to molecular weight changes than GPC.
 
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Anexo_A.pdf (115.64 Kbytes)
Publishing Date
2008-02-29
 
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