Abstract
A model is derived for the effect of physical aging on the linear viscoelastic response of amorphous polymers in the vicinity of the glass transition temperature Tg. A polymer is treated as an ensemble of flow units rearranged at random times. Any rearrangement event is thought of as a hop of a relaxing region trapped in its cage to some liquid-like state, where the region forgets its previous configuration. Stress-strain relations are developed and are verified by fitting observations in shear oscillation tests for poly(vinyl acetate). It is revealed that the inhomogeneity of the equilibrium energy landscape decreases with temperature and disappears at some crossover temperature Tc about 10 K above Tg. Kinetic equations are derived for out-of-equilibrium transformations of the energy landscape after cooling from above Tc to some temperature T in the sub-Tg region. It is evidenced that the Kohlrausch-Williams-Watt (KWW) formula ensures fair prediction of experimental data for aged specimens.
| Original language | English |
|---|---|
| Pages (from-to) | 48-64 |
| Number of pages | 17 |
| Journal | Computational Materials Science |
| Volume | 18 |
| Issue number | 1 |
| DOIs | |
| State | Published - 1 Jan 2000 |
| Externally published | Yes |
Keywords
- Cooperative rearrangement
- Glassy polymers
- Physical aging
- Trapping concept
- Viscoelasticity
ASJC Scopus subject areas
- General Computer Science
- General Chemistry
- General Materials Science
- Mechanics of Materials
- General Physics and Astronomy
- Computational Mathematics