Loss peaks, multiple relaxation

Relaxation profiles obtained as loss peak in imaginary dielectric curve and as step jump of real permittivity line Partial miscibility might exhibit multiple relaxation peaks overlaying or towards individual components, or display diverse relaxation rate even >T, Non-isothermal crystallization by isochronal temperature sweep DSC (cold crystallization and melting discernible as sudden drop and steep rise of static dielectric permittivity, respectively) Crystallization onset predicted using DRS relaxation time in coupUng model faster than the experimental time... 

Detects from a relaxation to subtle sub-Tg processes that show otherwise negligible change in heat capacity iP,Y etc.) Complementary to DSC, symmetrical and narrower loss peak for miscible system, multiple loss peaks for highly heterogeneous system Employs the quantifiable difference in mechanical response of crystalline and amorphous state of a material Need of a special sample geometry and amount, difficult to mount powder... 

F. 30. Cole-Cole circular plot of loss index against dielectric constant, (a) For a single relaxation time, (b) For multiple relaxation times, a = storage coefficient

dielectric constant at maximum loss (the loss peak). g = Static dielectric constant and < = bigh frequency dielectric constant. 

Ae with degradation is a useful measure of the accumulation of polar groups in the polymer. However, there appears to be considerable overlapping of multiple peaks, and in the early stages of the reaction, Ac, which Is determined from areas under curves in the e" vs 1/T plots is not readily accessible. The relaxation peaks are fairly S3immetrlcal and e" values at the frequency of maximum loss have been used as alternative data to follow reactions. 

Lastly, it is commonly assumed that the relaxation rate of all solute atoms is consistent, which is not the case for multiple compounds in a single sample (e.g. metabonomics). Calibrations must be applied to any standard database for identification based on relative rates of relaxation, and therefore intensity of peaks. Different functional groups in the same molecule can have different spin-lattice relaxation rates as would more flexible regions of large molecules. For extremely accurate measurements the calibration of signal loss is also frequency dependent (i.e. distance to carrier position is proportional to intensity variation) due to the profile of the hard pulses. 

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