SYNOPSISIn this article we consider characterization of the branching distribution of LLDPE by analytical TREF and by DSC techniques. Qualitatively, both methods yield parallel information, provided that the DSC samples are prepared at very slow cooling rates. Analytical TREF provides more quantitative information, however, in that the mass fraction of material with different branch levels can be estimated. Full characterization of a polyethylene requires the use of a preparative TREF technique, in which fractions dissolved at preselected temperatures are investigated for branching with high resolution 13C NMR and for molecular weight distribution, with high temperature SEC analyses.

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 process‐ability 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.