MODULATED TEMPERATURE ANALYSIS

Coleman NJ, Craig DQM. Modulated temperature differential scanning calorimetry A novel approach to pharmaceutical thermal analysis. Ini J Pharm 1996 135 13-29. 

The aim of this entry is to discuss the primary thermal analysis technique, TGA, in terms of the associated instrumentation, calibration procedures, and application range. Related techniques, such as TGA-DTA, EGA, SCTA, and modulated temperature TGA, are also discussed, as these reflect the significant developments of the TGA family of techniques that have occurred over the last decade. 

Such a differential heating program leads to increased sensitivity and resolution in TGA but also to a much increased time-frame for the analysis. Dynamic rate TG appears to have addressed both of these features and hence has much potential as a high resolution/ rapid thermal analysis system, which, unlike SCTA, can be applied for rapid and reproducible thermal analysis of a wide range of complex materials. Finally, modulated temperature thermogravimetrie analysis has enhanced potential for the kinetic analysis of thermal decomposition reactions over conventional TGA because of its greater resolution of thermal events. 

Modulated Temperature Differential Scanning Calorimetry Theory and Practical Applications in Polymer Characterisation, Vol. 6 Hot Topics in Thermal Analysis and Calorimetry, Eds., Reading, M. and Hourston, D.J., Springer-Verlag, Dordrecht, the Netherlands, 2006. 

The book opens with the first three chapters devoted to differential scanning calorimetry (DSC), the most commonly used thermal method. These chapters cover the principles, optimal use, and pharmaceutical applications of the method. Subsequent chapters explore modulated temperature DSC, thermogravimetric analysis, thermal microscopy, microcalorimetry, high sensitivity DSC, dynamic mechanical analysis, and thermally stimulated current, all of which have attracted great interest within the pharmaceutical field. Each chapter includes theoretical background, measurement optimization, and pharmaceutical applications. 

An extra tool is the possibility to construct Lissajoux figures by plotting, for instance, the modulated heat flow versus derivative modulated temperature. This provides additional information about the validity of the steady state conditions of the experiments, which is visualized by the retrace of the separate ellipses. In these specific Lissajoux figures the width corresponds to the phase lag and the slope to the specific heat. Under the conditions of analysis the ent py recovery peak is a nonreversing event and can therefore be separated fix>m the reversible changes of specific heat. 

The principle motivation behind the revision of this book resides in the burgeoning interest in temperature modulated thermal analysis methods. In this revised edition the sections on temperature modulated thermal analysis have been updated and considerably increased in size. We greatefully acknowledge stimulating discussions on TMDSC with Leonard C. Thomas and Marine Peron. 

The simplicity of the data analysis for a standard DSC is extended to modulated temperatures, as long as the condition of steady state and negligible temperature gradients within the sample can be maintained throughout the modulation. In Figure 4.15, the curves illustrate sinusoidal modulation. 

Other Temperature Modulated Thermal Analysis Techniques... 

In terms of modulated thermal analysis techniques , TMDSC clearly dominates the group. However, there is limited literature on temperature modulated thermogravimetic analysis (TMTGA) and temperature modulated thermomechanical analysis (TMTMA). Modulation principles have been applied to some less common thermal analysis techniques such as DMA and thermally stimulated current analysis and these developments will be briefly addressed here. It appears that the major development in thermal analysis in the next decade will be in the temperature modulated domain. 

Price DM (2000) Modulated temperature thermomechanical analysis. Thermochimica Acta 357-358 23-29. 

Novel mechanical tests are being developed and shown to be useful tools to investigate thermal and structural relaxation. These include the modulated-temperature-thermomechanometry technique (mT-TM) which has been recently employed to investigate blends of core cross-linked (CCS) PS and PMMA (Spoljaric et al. 2011) and nanomechanical thermal analysis. By using silicon microcantilever deflection measurements, the latter technique can provide a measure of temperature-dependent thermal stresses and therefore investigate the influence of physical aging (Yun et al. 2011). 

Since there is no complex Fourier transform involved in data deconvolution and no phase lag component to the analysis, the reported advantages include reliable and direct heat capacity measurement with low mass samples over a much shorter time than experiments performed in equivalent large mass heat flux modulated temperature DSC [8]. 

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