Table III. Dielectric Loss Peaks Observed at Several kHz of |

Figure 2. Secondary dielectric loss peaks (1 kHz) in cured I. |

Show that, according to the Debye model, the width of the dielectric loss peak e" plotted against frequency is 1.14 decades measured at half the peak height. [Pg.288]

The dielectric loss behavior of both polyethylene s Y transi-tion and polycarbonate s 0-transltion was enhanced by the presence of unassociated water. The area under the associated loss peak was found to increase in direct proportion to the concentration of unassociated water. In addition a secondary dielectric loss peak associated with frozen clustered water occurred in polycarbonate about 40°C below Its g-transition. Liquid clustered water at [Pg.451]

An analogous expression for the dielectric loss in terms of the derivative of the permittivity is commonly used to avoid the problem of dielectric loss peaks being masked by dc conductivity (the latter not contributing to the in-phase response) (Wubbenhorst and Van Tumhout, 2002). [Pg.291]

FIG. 13.29 Frequency-temperature correlation map for polystyrene, (o, ) mechanical loss peaks ( , ) dielectric loss peaks (A, ) NMR narrowing and T, (i.e. spin-lattice relaxation time) minima for (open symbols) atactic an (filled symbols) isotactic polystyrenes. From Yano and Wada (1971). Courtesy John Wiley Sons, Inc. [Pg.424]

The CD function indicates that the dielectric loss (e") of glycerol follows the power law e" /Pcd at high frequencies (f fmx), where/max is the frequency corresponding to the dielectric loss peak. However, the high-frequency experimental data in Fig. 24 demonstrate a significant deviation from the expected asymptotic behavior both for CD and KWW functions, e" values [Pg.51]

These observations underlie many of the empirical functions commonly used to describe dielectric loss peaks, for instance, the ones proposed by Cole and Cole (100), Davidson and Cole (101), and Havriliak and Negami (102). In the time domain, the empirical KWW relaxation function 0(t) oc exp[—(t/t) ] often provides a reasonable description of experimental data (103). Since the response function is calculated as the negative derivative of 0(t), it behaves as a power law for short times. Moreover, the ubiquitous occurrence of power laws in (dielectric) spectra explains why log-log representations often are preferable power laws present themselves as straight lines when a log-log scale is used. [Pg.444]

Do these critical frequencies associated with reproduction processes (or their ranges) correspond to the frequency of the dielectric loss peaks of [Pg.370]

As illustrated in some of these figures, all the a-loss peaks are well-fitted by the one-sided Fourier transform of the KWW over the main part of the dispersion. Thus, the experimental fact of constant dispersion at constant xa can be restated as the invariance of the fractional exponent KWW (or the coupling parameter n) at constant xa. In other words, xa and (or n) are co-invariants of changing thermodynamic conditions (T and P). If w is the full width at half-maximum of the dielectric loss peak normalized to that of an ideal Debye loss peak, there is an approximate relation between w and n given by n= 1.047(1 — w-1) [112], [Pg.508]

The temperature dependence of e and k in a roll-drawn and polarized PVDF was measured by Oshiki and Fukada (1971) and is illustrated in Fig. 28. Both quantities have maxima at — 20° C and 50° C where dielectric loss peaks are observed, due to primary and crystalline relaxations, respectively (Sasabe and others, 1969). [Pg.48]

Chiu (116) used the apparatus previously described to study the thermal decomposition of selected polymers such as polyethylene terephthalate), po y(vinyl fluoride), po y(vinylidene fluoride), and others. The dielectric constant curves of a group of fluorocarbon polymers are shown in Figure 11.33. As illustrated, the more polar polymers such as poly(vinylidinefiuoride) (PVDF) and poly(vinyl fluoride) (PVF) show characteristic dielectric loss peaks that are distinguishable from the relatively featureless and low-loss curves of the other polymers. For PVF, the low-temperature process is due [Pg.724]

In view of Table II the main difference of the parameters, fitted for HW, from those, fitted for OW, concerns (i) some increase of the libration amplitude / , (ii) decrease of the form factor /, (iii) decrease of the frequency vq (the center frequency of the T-band) and increase of the moment nq, responsible for this band, and (iv) decrease of the intensity factor gj, which strongly influences the THz band. Comparison of curves 3 in Figs. 4h and 5h shows that the partial dielectric loss peak g"max of HW, located at v near 150 cm-1 and stipulated by harmonic longitudinal vibration of HB molecules, substantially exceeds such a peak of OW, since the elastic dipole moment / (D20) 8.8 D exceeds the moment / (H20) 3.5 D. [Pg.365]

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