The factors affecting pressure losses during extrusion of polymer melts are
discussed in the present article. The rheological properties of an unvulca
nized rubber compound were examined by using a Monsanto processability test
er (MPT) under experimental conditions of temperatures varied 90 to 120 deg
reesC and shear rates from 10(2) to 10(3) s(-1). Furthermore, a set of dies
with different entry angle (2 alpha) was selected to identify the effects
of die angles on pressure losses in capillary extrusion of the sample fluid
. It was found that the total pressure drop (DeltaP) decreased when 2 alpha
< 75 degrees, and then increased with increasing 2<alpha>. The DeltaP reac
hed the minimum value when 2 alpha is around 75 degrees. It suggests that t
he natural converging angle of the sample fluid be about 75 degrees under t
he experimental conditions, according to the research results presented in
previous work. (C) 2001 John Wiley & Sons, Inc.