ELONGATIONAL FLOW PROPERTIES OF LOW-DENSITY POLYETHYLENE AND LINEAR LOW-DENSITY POLYETHYLENE FROM NONISOTHERMAL MELT-SPINNING EXPERIMENTS

Low-density polyethylene (LDPE) and also Linear low-density polyethylene (LLDPE) resins can be characterized by the degree of strain hardening and down-gaging during elongation. A new method for the determination of the apparent elongational flow characteristics is presented. In a small scale apparatus, a molten monofilament is stretched under nonisothermal conditions similar to those found in tubular film extrusion. Measurement of resistance to elongational flow and apparent elongational strain rates permit the comparison of the processability of different resins under specified conditions. The effect of melt temperature and extension ratio are examined. The importance of the molecular structure of both LDPE and LLDPE resins on these properties is also outlined.