Relaxation below

There are no available data to establish whether nonconductive, low viscosity chemical products such as ethyl ether similarly display hyperbolic relaxation below about 2 pS/m, or even whether this phenomenon is a practical reality for such liquids. Should Ohmic relaxation behavior continue to much less than 0.5 pS/m the risk of static accumulation would be enhanced compared with petroleum distillates. 

Roudaut, G., Maglione, M., and Le Meste, M. 1999b. Relaxations below glass transition temperature in bread and its components. Cereal Chem. 76, 78-81. 

The NMRD profile of chromium(III) aqua ion (Fig. 18) is characterized by slow exchanging water protons, as clearly shown by the fact that the solvent proton relaxivity at low fields increases with increasing the temperature. The occurrence of slow exchange hinders any increase in relaxivity below 300 K, thus explaining the fact that the contact dispersion disappears in the low temperature profiles, whereas it is well shown in the high temperature profiles, as already discussed in Section I.C.8. 

The mechanical properties of Shell Kraton 102 were determined in tensile creep and stress relaxation. Below 15°C the temperature dependence is described by a WLF equation. Here the polystyrene domains act as inert filler. Above 15°C the temperature dependence reflects added contributions from the polystyrene domains. The shift factors, after the WLF contribution, obeyed Arrhenius equations (AHa = 35 and 39 kcal/mole). From plots of the creep data shifted according to the WLF equation, the added compliance could be obtained and its temperature dependence determined independently. It obeyed an Arrhenius equation ( AHa = 37 kcal/mole). Plots of the compliances derived from the relaxation measurements after conversion to creep data gave the same activation energy. Thus, the compliances are additive in determining the mechanical behavior. 

In order to assess the orientational stability of the poled state, the temperature dependence of the dipole mobility of the side groups was examined through dielectric relaxation measurements. (13) No low temperature relaxation below Tg was observed in the frequency range studied (100 Hz-100 kHz). In addition, the dielectric constant was approximately equal to the square of the refractive index, indicating that below T only electronic and no significant orientational contributions to the dielectric displacement are present. Thus, it was expected that a given orientational state of the ensemble would be stable at temperatures significantly below Tg. 

DSC and DTA. They can be used to confirm suspicious glass transitions revealed by DSC and most important, they can further quantify molecular mobility associated with sub-glass transitions. For example, DSC analysis of poly (ethylene 2,6-naphthalene dicarboxylate) (PEN) only revealed the presence of a glass transition around 112 °C (Hardy et al., 2001). DMA analysis of the same sample, however, revealed two secondary relaxations below this glass transition (Hardy et al., 2001). In the case of humic materials, it is not uncommon for DSC to fail to detect clear thermal transitions due to their heterogeneous nature, which contributes to overlap/ broadening or washout of thermal transitions. As such,TMA and DMA represent powerful, complementary tools to DSC. 

Polymers derived from itaconic acid show several relaxations below room temperature [245], When these polymers contain cyclohexyl groups in the side chain like... 

Therefore, yr(a ) decays rapidly near a>0, as (a>0 — coherent reflection on the two faces creates interference modulation of the emission, visible in Fig. 2.17 and formally included in (2.138). In a complementary way, phonon relaxation in the vicinity of 0 dominates the photon relaxation. Then, as the energy decays below E0, y,(co) increases and ( (- Ef) decreases very rapidly, the radiative rate yr(a>) overwhelming the polariton relaxation below an energy threshold which depends on the crystal thickness and on the temperature.90... 

Equations proposed by Struik (1977,1978) that are able to describe experimental stress relaxation below Tg are for short-time experiments... 

By including the effect of volume relaxation below Tg, calculations of the PVT properties of amorphous polymer have been extended from the equilibrium liquid to nonequilibrium glassy states. The study reveals the effects of kinetic, pressure, and stresses on Tg, which depends on relaxation time. 

The flow is either entirely cocurrent or countercurrent, as shown in Figures 6.42a, 6.42b, 6.43a, and 6.43b. This assumption is relaxed below for many multipass or cross-flow heat exchangers. 

MDI. Three low temperature transition maxima are found in the loss modulus (G") of the 73-series Halthanes (see Fig. 1). Two low temperature secondary relaxations below the glass transition of the soft segment are arbitrarily labeled Tp (-100°C) and Ty (-155°C). These relaxations are probably associated with molecular motions in the urethane (9) and polyether (10) components of the soft segment, respectively. The glass transition of the soft segment occurs at about -50°C and is responsible for the drop in the storage modulus G1 by two orders of magnitude. 

Finally, the question of relaxation below T, and its relation to fragility requires comment. Experimental data suggest that pharmaceuticals are moderately fragile above T , but there seems to be no a priori reason... 

The isotropic reorientation of the hydrated complex has the same T value as that found for sugars by relaxation. Below 270 K, no dynamic equilibrium between bulk and hydrate water is detected the correlation times diverge and values are no longer identical. 

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