FREITAS, D. M. G.; FREITAS, DANIEL M. G.; FREITAS, DANIEL MULLER G.; http://lattes.cnpq.br/2978708212879839; FREITAS, Daniel Muller Gomes de.
Resumo:
The polyethylene presents a high degree of diversity in relation to the molecular
structure, being able to present long and short branches and varied molecular
weight distribution, which affects its rheological behavior. The study of the
rheological properties, such as apparent viscosity, shear stress and extrudate
swelling of HDPE/LLDPE blends is extremely important in order to determine
ideal processing conditions and obtain control over the flow instabilities present
in polymers at shear rates employed during processing. This work aims to study
the rheological behavior and flow instabilities of polyethylene blends from
renewable sources (HDPE/LLDPE) at low and high strain rates. The effects of
LLDPE concentration and strain rate on extrudate swelling and flow instability
were investigated. In all the analyzed compositions there was an increase of the
extrudate swelling with the increase of the deformation rate. For pure PELBD
and higher PELBD blends, swelling was attenuated by the emergence of
sharkskin type flow instabilities, stick-slip and gross melt fracture. Extrudate
swelling corroborated the damping coefficient (tan ) where LLDPE, which
exhibits more elastic behavior, exhibits greater extrudate swelling.