Melt elasticity of low density polyethylene

The stress vs strain and strain recovery characteristics of a series of low density polyethylenes of various molecular size and molecular size distributions have been studied in the melt state. The results show that the high molecular size portion of the molecular size distribution dominates the stress vs strain behavior. The high molecular size component causes a large increase in the stress overshoot and steady state stress. The high molecular size component also has a strong influence on the magnitude of recoverable strain, The strain recovery characteristics are dependent on the amount of strain applied. For large strains (above the yield point) the strain recovers slowly to a large extent (Type I). For applied strains below the yield point the strain recovery is rapid and finished in a short period of time (Type II).