Abstract
The pom-pom rheological constitutive equation for branched polymers proposed by McLeish and Larson is evaluated in step shear strain flows. Semianalytic expressions for the shear-stress relaxation modulus are derived for both the integral and approximate differential versions of the pom-pom model. Predictions from the thermodynamically motivated differential pompon model of Öttinger are also examined. Single-mode integral and differential pom-pom models are found to give qualitatively different predictions, the former displays time-strain factorability after the backbone stretch is relaxed, while the latter does not. We also find that the differential pompon model gives quantitatively similar predictions to the integral pom-pom model in step strain flows. Predictions from multimode integral and differential pom-pom models are compared with experimental data on a widely characterized, low-density polyethylene known as 1810H. The experiments strongly support time-strain factorability, while the multimode pom-pom model predictions show deviations from this behavior over the entire range of time that is experimentally accessible.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 123-131 |
| Number of pages | 9 |
| Journal | Rheologica Acta |
| Volume | 42 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 2003 |
| Externally published | Yes |
All Science Journal Classification (ASJC) codes
- General Materials Science
- Condensed Matter Physics
Keywords
- Branched polymer
- Pom-pom model
- Step-strain flow