Scaling parameters dielectric relaxation

The relaxation time constant 0 would also influence the parameter A, finally p substantially. From either Eq.(73) and (75), one will find that p increases as 0 increases, that is, the ER effect will be stronger if the dielectric relaxation is slower. However, too slow relaxation time (tlien the slow response time) would make FR fluids useless. Generally, the FR response time around 1 millisecond is favorable, thus requiring the relaxation time be of the same time scale, i.e., the dielectric relaxation frequency around lO llz. Block presumably thought the polarization rate would be important in the ER response process, and too fast or too slow polarization is unfavorable to the ER effect [7J. Ikazaki and Kawai experimentally found that the FR fluids of the relaxation frequencies within the range 100-10 Hz would exhibit a large ER effect [21,31], supporting the derivation from Eq. (69). 

The dielectric loss relaxation spectrum e"( )/ was shown to be uniformly accurately described by EQxp(—aa> ) at smaller frequencies and ea> at larger frequencies. For a small 38 kDa poly(D,L-lactic) acid, the scaling parameters are substantially independent of c with a larger 119 kDa poly(D,L-lactic) acid, a increases with increasing c. The parameter S is often but not always equal to unity when 5 = 1, a is a true time. At elevated polymer concentration, the exponent x is smaller correspondingly, dielectric loss relaxation spectra become broader. 

Figure 46. Linearized plots of the three parameters xa, vmin, and %min, determined from the MCT analyses of the relaxation spectrum in the high-temperature regime. Plotted are the scaling law amplitude (SLA) as indicated (a) from the dielectric spectra of glycerol (cf. Fig. 18a) (adapted from Ref. 136) (b) from the light scattering spectra of 2-picoline (cf. Fig. 18b) (from Ref. 183).

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