Viscous flow and degradation of molten polypropylene

Abstract

The melt extrusion of a commercial polypropylene resin was studied with a screw extruder and a series of capillary dies of length:radius ratios varying from 0 to 65. Three temperatures and the range of shear rates encountered in industrial processing were covered. The temperature dependence of the apparent melt viscosity of polypropylene was intermediate between linear and branched polyethylene. Extrapolated zero shear activation energy for viscous flow was 9 ± 1 Kcal/mole. Shear dependence of the apparent viscosity of polypropylene melt was greater than for branched polyethylene in turn, greater for linear.

Capillary viscometry of molten polycaprolactam

“…6), as is known to occur also for other polymers. 22 The effect of water on the process is particularly important (see lcig. 7).…”