TMDSC heat capacity, complex

As a result the heat capacity measured by TMDSC can be considered as a complex heat capacity and is denoted complex heat capacity has two components a component that is in-phase with... 

If time-dependent processes are involved, then the process is clearly outside the scope of classical thermodynamics. The time-dependent (apparent) heat capacity, measured with, say, TMDSC would lead to time-dependent potential functions which must be interpreted in terms of irreversible thermodynamics. In such cases, a nonzero imaginary part of the complex heat capacity exists which is linked to the entropy production of the process in question (for details see [32]). Thus, temperature-modulated calorimetry makes it possible to determine time-dependent (irreversible) thermodynamic quantities. 

The temp, modulated DSC (TMDSC) technique could be used for heat capacity spectroscopy in the low frequency range. The measured property was the complex heat capacity. The frequency-dependent relaxation transition measured by TMDSC occurred in the temp, range of the thermal Tg. The non-equilibrium of the glassy state thus influenced the TMDSC curves. Experimental evidence was the dependence of the shape of the heat capacity curve on the thermal history. A theoretical description of the influence of the non-equilibrium state on the spectroscopic curves, based on the Tool-Narayanaswamy-Moynihan model, is presented. 23 refs. 

The non-isothermal crystallisation of PETP was examined by temp, modulated DSC(TMDSC). A new analytical model of TMDSC was applied to the process, taking account of the response of exothermic heat flow to temp, modulation in an apparent heat capacity of complex quantity. By examining the frequency dependence of the apparent heat capacity, the applicability was successfully examined for the non-isothermal process. The method was capable of determining the temp, dependence of crystal growth rate from TMDSC data analysis. The results were in good agreement with the dependence determined from literature values of spherulite growth rate measured by optical microscopy. 12 refs. 

Figure 6 Complex specific heat capacity for PS measured by TMDSC (c p(co), c"p(co)) and total heat capacity from the underiying linear scan at a cooling rate po (total Cp(po)). Measuring conditions temperature modulation amplitude Ay = 0.5 K, angularfrequency cu = 2n/fp, period fp = 60s, underlying the scanning rate po = -0.25Kmin" Reproduced with permission from Hensel, A. Schick, C. J. Non-Ciystal. So/ cfs1998,235-237, 510-516. 2...

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