http://lattes.cnpq.br/8562091525519918; http://lattes.cnpq.br/8562091525519918; MÉLO, Tomás Jeferson Alves de.
Abstract:
In this work, the system PP, Attapulgite was studied by capillary rheolog>' at 5-
25% filler content and temperatures of 180, 200 and 220°C at shearing rates compatible to
those involved in injection and extrusion processes, i.e., 11,64 to 2327,12 s'1. Shear stress
and shear rates experimentally obtained for ali composites as well as those of straight
polypropylene were correlated to the Ostwald de Waele model. The same was done for the
experimentaly determined apparent viscosity and corrected shear rate. The influence of
attapulgite concentracion, shear rate and temperature on the processability of the
composite's and of the matrix were investigated by observing the flow curves, power
index, consistency index and apparent viscosity.
Our results show that the rheological model of Ostwald de Waele successfully
described the flow behavior of PP and PP/attapulgite system under the experimental
shearing conditions employed. The study shows that pseudoplasticity increased with
temperature up to 15% w/w attapulgite content becaming insensitive to both concentracion
and temperature at higher filler contents. The consistency index (K) increased with
attapulgite concentracion and decreased with temperature increments. Apparent viscosity
increased with filler content, and decreased with increasing temperature and shear rates,
which characterize pseudoplastic behavior. At higher temperature and shear rates the
apparent viscosity of ali composites teaded to a single value which shows that although
attapulgite addition doe increase PP viscosity it does was change its processabillity at shear
rates above 3000 s*1 at temperatures of 200 and 220°C.