Chain flow in thermo-stimulated creep experiments: application to poly(methyl methacrylate)

Abstract

Abstract Experimental data from thermo-stimulated creep (TSCr) spectrometry display a retardation mode in poly(methyl methacrylate) (PMMA) at T > Tg (glass transition temperature). In this work an attempt is made to relate the restoring force involved during TSCr measurements beyond the glass transition zone to the viscoelastic behaviour of the polymeric chains flowing in the entangled network. In order to determine the temperature dependence of the molecular relaxation time, or lifetime for monomer diffusion, τmol, three different sources of viscoelastic measurements are used. The TSCr data are then mapped onto the Arrhenius diagram of log τmol to deduce the corresponding terminal relaxation time, or flow time, τflow. Comparison between the terminal relaxation time and the characteristic time of TSCr spectrometry shows that, during the temperature scan, the recovery of the frozen-in strain can be effectively well described by the long-range diffusion of macromolecular chains within the surrounding entanglement lattice.