1975 Volume 3 Issue 2 Pages 64-70
The present study is an experimental investigation of the effects of the kinds and dimensions of dispersed fillers on the capillary flow behavior of a polypropylene. Two kinds of fillers were used: glass-fibers with two different fiberlengths, and glass-beads with two different diameters.
The results may be summarized as follows:
(1) The coefficient of viscosity of melts with dispersed fillers under a constant shear rate of 1 sec-1 increased with the increase of content of fillers, and the effects of filler content on the viscosity in the case of glass-fiber dispersed melts were generally larger than for melts containing glass beads. And the relation between the increasing of viscosity of fillers and volumetric content of fillers in the case of longer glass-fiber was larger than the calculated value using theoretical equations, such as those of Einstein and of Guth and Smallwood.
(2) The viscosity increase with the dispersion of fillers decreased noticeably with the increase of shear rate.
The relation between the relative viscosity and shear rate was represented by a master curve, which was obtained by moderate shifting on the horizontal axis of shear rate.
(3) The pressure loss at the capillary inlet increased with the increase of filler content at low temperature such as 180°C, but the effects of fillers upon the pressure losses were generally complex at high temperatures such as 210°C.
(4) The die swell ratio for filled melts was smaller than that of non-filled melts. The decrease of the die swell ratio of filled melts seems to be affected not only by the decrease of the volume ratio of resin in the system but also by the accelerated orientation of filler induced by flowing in the case of glass-fiber fillers.