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

Abstract

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.

Novel High-Viscosity Polyacrylamidated Chitosan for Neural Tissue Engineering: Fabrication of Anisotropic Neurodurable Scaffold via Molecular Disposition of Persulfate-Mediated Polymer Slicing and Complexation

“…DSC was used to measure and compare the thermal transitions inherent to the synthesized copolymers as a function of temperature thereby directly measuring different heat flows between the reference (AAm-g-CHT) and sample (PAAm-g-CHT) [29]. The DSC curves of the copolymers are depicted in Figure 2 revealing three thermal transitions.…”

TSDC of Irradiated and Non-Irradiated Cellulose Acetate

“…The distribution of relaxation times is usually used to describe the phenomenon of relaxation in the polymer, and then analysis of complex TSDC spectra is performed using the appropriate parameter related to the symmetry and the shape of the distribution of relaxation times that characterize these modes [26][27][28]. Hence, thermal sampling (TS) technique has been carried out [29][30][31] to resolve complex TSDC modes experimentally and therefore, the dielectric relaxation times distribution. To obtain a more accurate and deeper insight into the relaxation behavior of the non-irradiated and irradiated cellulose acetate (CA) samples, the global TSDC spectra were decomposed into their elementary spectrum with TS technique in the poling temperature range from 318 to 353 K, with a temperature window, Tp-Td = 5K for each spectrum.…”

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“…This composite will be fibrous composite. Dispersed phase of this composite is fiber which will improve strength, stiffness and fracture toughness of composite [10][11][12]. Matrix in such materials serves not only as a binder of the fibers but also keeping them in a desired shape and protecting them from mechanical or chemical damages.…”