Secondary relaxation processes in polyethylene terephthalate–additive blends: 2. Dynamic mechanical and dielectric investigations

Characterization, structural transitions and properties of a tightly crosslinked polythiourethane network for optical applications

“…More interestingly ∆S ≠ap can be considered as an indication of motional cooperativity. Values of the order of 100 kJ/mol correspond to a rather high motional cooperativity, comparable with those obtained in epoxy-amine thermosetting polymers [30,31,35], in which the cooperative modes were shown to extend over more than six units. Thus, as in epoxy-amine systems, the β relaxation motions in polythiourethane densely crosslinked networks result from a distribution of motions, which was shown to be a general phenomenon of the secondary modes in polymers [36].…”

“…As shown in numerous studies on the β secondary transition in epoxy networks, the impossibility of drawing a consistent master curve all over the β transition E" peak drawn at different frequencies is indicative of the existence of different types of motions [28][29][30]. On the contrary successful building of a master curve is regarded as evidence for a simple motional behaviour in the whole temperature range corresponding to the β transition.…”

The analysis of isothermal current in terms of charge injection or extraction at the metal–dielectric contact

“…It is obvious that by charging the sample at 40 K, the applied electric polarization field is not sufficient to rotate the dipoles that will randomize at 240 or 290 K. But the space charge injected into the sample at 40 K may by trapped in deep traps and it will be released around 240 and 290 K when the thermal motion of the molecules is strong enough. We have to accept that the b relaxation is due to the motion of the phenyl ring as observed by Nuclear Magnetic Resonance and AC dielectric measurements [17]. The relaxation around 240 K is related to phenyl ring movement in the amorphous phase and the relaxation around 290 K is related to the movement in the crystalline phase.…”

Secondary Retardation/Relaxation Processes in Bisphenol A Polycarbonate: Thermostimulated Creep and Dynamic Mechanical Analysis Combined Investigations

“…This phenomenon has also been observed for PET, whose bimodal behavior disappears for high frequencies. [28] CONCLUSION In this work, we have shown the interest of thermostimulated creep for the mechanical characterization of an amorphous polymer (polycarbonate). In the very low frequency range, this technique is a good complement to more classical techniques like DMA.…”