MEASUREMENT OF ELONGATION VISCOSITY FOR POLYMER MELTS BY FIBER SPINNING

The elongation behavior of various polymer melts extruded from the sin gle screw extruder has been studied. Low-density polyethylene, high-de nsity polyethylene, polypropylene, and their short glass-fiber (GF)-fi lled composites were used. It was found that the spinning stability wa s good but the drawability was poor for GF-filled polymers. The elonga tion viscosity was measured by use of a Gottfert tensiometer (Rheotens ) in the strain rate range from 0.1 to 4 s(-1). In regard to the visco sity calculations, a very convenient and straightforward method, espec ially for molten materials without die swell, is presented. All the sa mple melts showed slight tension thinning; that is, the elongation vis cosity decreased along with the strain rate. It was also found that th e elongation viscosity of the GF-filled polymer may increase along wit h the fiber content up to a critical value, and then drop if more fibe r is added. The influence of the die geometry on the viscosity measure ment is discussed. (C) 1997 John Wiley & Sons, Inc.