The Creep and Recoverable Compliances

Figure 5.9 shows the creep and recoverable compliances of a metallocene, linear, low-density polyethylene at 150 °C [36]. This polymer has a polydispersity index (Af, /M ) of about two. The data shown start in the transition from the plateau to the terminal zones, and the last few points are in the terminal zone, which corresponds here to steady flow. Note that the experiment had to be continued for about 2.5 hours to reach steady state, where J t) = /° +tlr)g and /j (f) = /°. (/r is the recoverable compliance defined in Eq. 4.26.) It is of interest to compare the creep compliance of an entangled polymer melt with that of a cross-linked elastomer. The latter cannot flow, so at long times /(t) approaches a constant value, the equilibrium compliance, /°. 

---