Ai. Isayev et al., INJECTION-MOLDING OF SEMICRYSTALLINE POLYMERS .1. MATERIAL CHARACTERIZATION, Journal of applied polymer science, 55(5), 1995, pp. 807-819
Various material data for an isotactic polypropylene were acquired for
the simulation of the injection molding of this material. Viscosity a
s a function of shear rate and temperature was measured using a capill
ary rheometer at high shear rates and a cone-and-plate rheometer at lo
w shear rates. Heat-flow properties, characterizing kinetics and induc
tion time of quiescent crystallization, were obtained from DSC measure
ments. Material data characterizing shear-induced crystallization were
obtained from extrusion experiments through a slit die with subsequen
t quenching of the material in the die after various rest times. The t
hickness of the shear-induced crystallization layer was measured along
with the birefringence in this layer. A model of shear-induced crysta
llization developed by Janeschitz-Kriegl and co-workers was used to fi
t the kinetic data. Thus, kinetic parameters such as the limiting shea
r rate below which no shear-induced crystallization can occur and the
characteristic time for the relaxation of birefringence were obtained.
(C) 1995 John Wiley & Sons, Inc.