Multiplicity of dielectric relaxation times of dispersed ice microcrystals

Pissis, P.; Apekis, L.; Christodoulides, C.

doi:10.1007/bf02451177

Cited by 10 publications

(10 citation statements)

References 19 publications

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“…The TS technique consists of "sampling" the relaxation process within a narrow temperature range by polarizing at a temperature T p and depolarizing at a temperature T d , a few degrees lower than T p . 18,27 Representative TS responses are shown in Figure 7, the values of E and o are listed in Table III. E was calculated by using the expression…”

Section: Thermally Stimulated Depolarization Currents (Tsdc) Measuremmentioning

confidence: 99%

Structure-property relationships in thermoplastic-apparent interpenetrating polymer networks based on crystallizable polyurethane and styrene-acrylic acid copolymer

Kyritsis

Pissis

Grigorieva

et al. 1999

J. Appl. Polym. Sci.

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Structure-property relationships in thermoplastic-apparent interpenetrating polymer networks (t-AIPNs), prepared by mechanical blending in a common solvent of crystallizable polyurethane (CPU) and styrene/acrylic acid random copolymer (S/AA), were investigated by means of wide-angle and small-angle X-ray scattering (WAXS and SAXS), dynamic mechanical analysis (DMA), thermally stimulated depolarization currents (TSDC) techniques, dielectric relaxation spectroscopy (DRS), and density, water uptake, deformation, and strength characteristics measurements. Several mechanical and dielectric relaxations of the pure components were characterized, and the effects thereupon induced by blending were followed. The two components show weak affinity to each other. The t-AIPNs can be classified into two groups with high and low contents of CPU, showing essentially the behavior of CPU and of S/AA, respectively. On the other hand, deviations from additivity in several properties indicate interactions between the two components, caused by the formation of H-bonds between their functional groups, and resulting in partial miscibility. In addition, significant changes are observed on some properties of the t-AIPNs on addition of small amounts of either of the components.

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Section: Thermally Stimulated Depolarization Currents (Tsdc) Measuremmentioning

confidence: 99%

Structure-property relationships in thermoplastic-apparent interpenetrating polymer networks based on crystallizable polyurethane and styrene-acrylic acid copolymer

Kyritsis

Pissis

Grigorieva

et al. 1999

J. Appl. Polym. Sci.

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“…It is interesting to note that ice samples with high content of disturbance produced either by very rapid crystal growth or from the high-pressure polymorphs Ice II and IX behave, in this respect, similar to ice dispersions [14,15]. Moreover, ice dispersions [8], ice samples with high content of disturbance [14,15] and HF-doped ice samples [21] have W values very close to each other, (0.34 + 0.37) eV. In deep polar ice W is 0.25eV at -7~ compared to 0.62 eV in single ice crystals at the same temperature.…”

Section: -Introductionmentioning

confidence: 93%

“…On the other hand, these relatively simple and easy to manipulate systems may serve as models for more complicated systems, such as food emulsions and tissue. The TSDC method, its equations, the methods of evaluating the activation energy W for the dipole reorientation and the pre-exponential factor ~o in the Arrhenius equation as well as the experimental apparatus used have already been described in [8]. Here we recall briefly the TSDC procedure.…”

Section: -Introductionmentioning

confidence: 99%

“…The low-temperature TSDC peak was found to be at each stage of evolution multiple due to a continuous distribution of relaxation times with both parameters in the Arrhenius equation, the activation energy W and the pre-exponential factor To, being continuously distributed [8,9]. The spectra of TM, W and To were obtained at selected stages of evolution by using the thermal sampling technique [8,9] and the mean values of W and To were determined at these stages.…”

Section: -Introductionmentioning

confidence: 99%

“…The spectra of TM, W and To were obtained at selected stages of evolution by using the thermal sampling technique [8,9] and the mean values of W and To were determined at these stages. It was found that with advancing stage of evolution, i.e.…”

Section: -Introductionmentioning

confidence: 99%

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Evolution with time of the dielectric properties of dispersed ice microcrystals

1991

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Summary. --The evolution with time of the characteristics of the dielectric relaxation of water molecules in dispersions of ice microcrystals has been studied by means of the thermally stimulated depolarization current (TSDC) method. With advancing stage of evolution, i.e. with increasing preservation time at constant preservation temperature and with increasing preservation temperature at constant preservation time, the mean values of relaxation time and activation energy have been found to decrease. The extent and the rate of the evolution have been compared to those in other forms of ice: ice samples with high content of disturbance, polycrystalline ice samples and single ice crystals. The observed similarities and differences in the behaviour of the different ice forms have been discussed in terms of the influence of extrinsic physical and chemical defects on the generation and motion of orientational Bjerrum defects.PACS 77.30 -Polarization and depolarization effects. PACS 82.70 -Disperse systems.

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Depolarization thermocurrent studies in poly(hydroxyethyl acrylate)/water hydrogels

Kyritsis

Pissis

Ribelles

et al. 1994

J Polym Sci B Polym Phys

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Detailed investigations on the dielectric relaxation mechanisms in poly(hydroxyethyl acrylate) (PHEA), by means of the thermally stimulated depolarization currents (TSDC) method in the temperature range 77‐300 K are reported. There is particular interest in the dependence of the dielectric relaxation mechanisms on the water content h, h = 0 − 0.5 w/w, in an attempt to contribute to a better understanding of the physical structure of water in the PHEA hydrogels. We employ thermal sampling (TS) and partial heating (PH) techniques to experimentally analyze the observed complex relaxation processes, due to the secondary (βsw) and the main (α) relaxation, into approximately single responses and to determine the spectra of activation energies E(T) at different h values. Measurements with different electrode configurations reveal different aspects of the dynamics of the relaxation mechanisms and allow the distinction between dipolar and conductivity relaxation contributions. It is shown that by means of these techniques we can determine certain temperature characteristics for the α relaxation and investigate their dependence on water content. We discuss the relation of these characteristic temperatures to the calorimetric glass transition temperature Tg. © 1994 John Wiley & Sons, Inc.

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Multiplicity of dielectric relaxation times of dispersed ice microcrystals

Cited by 10 publications

References 19 publications

Structure-property relationships in thermoplastic-apparent interpenetrating polymer networks based on crystallizable polyurethane and styrene-acrylic acid copolymer

Structure-property relationships in thermoplastic-apparent interpenetrating polymer networks based on crystallizable polyurethane and styrene-acrylic acid copolymer

Evolution with time of the dielectric properties of dispersed ice microcrystals

Depolarization thermocurrent studies in poly(hydroxyethyl acrylate)/water hydrogels

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