Modeling of the linear viscoelastic behavior of low-density polyethylene

We predict the linear viscoelastic behavior of low-density polyethylene from both the molecular-weight distribution and the individual structure of each species in the sample. The "structure map" of the samples was derived from SEC measurements. This map is a three-dimensional representation of the seniority distribution, and represents the probability of existence of a segment with seniority i in a molecule of molecular weight M. Moreover, results from the kinetics of the free radical polymerization of polyethylene show that the molecular weight of the segments increases according to their seniority. Finally, tube dilatation was generalized to the case of polydisperse samples. The solvent behavior of the relaxed segments was included through a continuous function of time that describes the instantaneous state of the entanglement network in the sample. The comparison between the theoretical predictions and the experimental data shows a good agreement over the whole experimental frequency range. (c) 2005 Wiley Periodicals, Inc.