Evaluation of rheological constitutive equations for branched polymers in step shear strain flows

摘要: The pom-pom rheological constitutive equation for branched polymers proposed by McLeish and Larson is evaluated in step shear strain flows. Semianalytic expressions the shear-stress relaxation modulus are derived both integral approximate differential versions of model. Predictions from thermodynamically motivated pompon model Ottinger also examined. Single-mode models found to give qualitatively different predictions, former displays time–strain factorability after backbone stretch relaxed, while latter does not. We find that gives quantitatively similar predictions multimode compared with experimental data on a widely characterized, low-density polyethylene known as 1810H. experiments strongly support factorability, show deviations this behavior over entire range time experimentally accessible.