Study of the Molecular Mobility in Polymers with the Thermally Stimulated Recovery Technique—A Review

Thermally stimulated recovery (TSR) is a non‐conventional mechanical spectroscopy technique that allows to analyse in detail the relaxation processes of polymeric systems in the low frequency region. This work reviews the main aspects and potentialities of this technique. The different kinds of TSR experiments that can be performed, global and thermal sampling (TS) experiments, are described and illustrated with several examples. Also, the different methods for the determination of the thermokinetic parameters (activation energy and pre‐exponential factor) of the thermal sampling (TS) procedure are explained and compared. In this context, the compensation phenomenon, which always appears in TSR results when the studies are performed in the glass transition region of a given system, is discussed. Examples of the application of this technique to different polymeric systems during the last 20 years are provided. An emphasis will be made on the analysis of the effect of crystallinity degree and crosslink density on the TSR response. A comparison between the results (characteristic times and activation energies) obtained by different techniques, namely TSR, dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC), is made.

Keywords:

• thermally stimulated recovery (TSR)
• non‐conventional mechanical spectroscopy technique
• global and thermal (TS) sampling experiments
• thermokinetic parameters
• compensation phenomenon
• crystallinity degree
• crosslink density
• dynamic mechanical analysis (DMA)
• differential scanning calorimetry

Acknowledgements

Financial support for this work was provided by FCT, through the POCTI and FEDER programmes. JLGR wish to acknowledge the support of the Spanish Science and Technology Ministry through the MAT2001‐2678‐C02‐01 project.