Study of rheological properties of polypropylenes in shear and elongational flows. / Estudo das propriedades reológicas de polipropilenos em fluxos de cisalhamento e fluxos elongacionais.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

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.

ASSUNTO(S)

reologia polímeros plymers polypropylene viscosidade polipropileno viscosity rheology

ACESSO AO ARTIGO

Documentos Relacionados