Temperature-modulated calorimetry

B. Wunderlich. Temperature Modulated Calorimetry in the 21st Century. Ther-mochim. Acta 2000, 355, 43-57. 

Wunderlich has also comprehensively reviewed the development of temperature modulated calorimetry into the 21st century in conjuction with its predicted scope for further application in the physical, chemical, and materials sciences. 

C. Schick and G. W. H. Hohne (ed.). Special Issue Temperature Modulated Calorimetry, Thermochim. Acta, 1997,304/305,1-378. 

Temperature-Modulated Calorimetry of the Frequency Dependence of the Glass Transition of Poly(ethylene terephthalate) and Polystyrene... 

Glass transitions involve mainly the onset or freezing of cooperative, large-amplitude motion and can be studied using thermal analysis. Temperature-modulated calorimetry, TMC, is a new technique that permits to measure the apparent, fiequency-dependent heat capacity. The method is described and a quasi-isodiermal measurement method is used to derive kinetic parameters of the glass transitions of poly(ethylene terephthalate) and polystyrene. A first-order kinetics expression can describe the approach to equilibrium and points to the limits caused by asymmetry and cooperativity of the kinetics. Activation energies vary from 75 to 350 kJ/mol, dependent on thermal pretreatment. The preexponential factor is, however, correlated with the activation energy. 

Gaur U, Pultz G, Wiedemeier H, Wunderlich B (1981) Analysis of the Heat Capacities of Group IV Chalcogenides using Debye Temperatures. J Thermal Anal 21 309-326. Baur H, Wunderlich B (1998) About Complex Heat Capacities and Temperature-modulated Calorimetry. J Thermal Anal and Calorimetry 54 437 65. 

Wunderlich B (2000) Temperature-modulated Calorimetry in the 2P Century. Thermochim Acta 355 43-57. 

This concludes the discussion of thermometry and dilatometry. The tools to measure temperature, length, and volume have now been analyzed. The tools for measurement of heat, the central theme of this book, will take the next three sections and deal with calorimetry, differential scanning calorimetry, and temperature-modulated calorimetry. The mechanical properties which involve dilatometry of systems exposed to different and changing forces, ate summarized in Sect. 4.5. The measurement of the final basic variable of state, mass, is treated in Sect. 4.6 which deals with thermogravimetry. 

Calorimetry involves the measurement of the extensive quantity heat. Its name derives from the middle of the 18 century when heat was called the caloric, as described in Sects. 1.1.1 and 2.1.1. As the main thermal-analysis method, calorimetry is discussed in this and the following two sections, covering classical calorimetry in Sect. 4.2, differential scanning calorimetry (DSC) in Sect. 4.3, and the more recent temperature-modulated calorimetry (TMC) in Sect. 4.4. 

Based on the measurement of the stress, a, resulting on the application of periodic strain, e, with equipment as shown in Fig. 4.155, one can develop a simple formalism of viscoelasticity that permits the extraction of the in-phase modulus, G, the storage modulus, and the out-of-phase modulus, G", the loss modulus. This description is analogous to the treatment of the heat capacity measured by temperature-modulated calorimetry as discussed with Fig. 4.161 of Sect. 4.5. The ratio G7G is the loss tangent, tan 6. The equations for the stress o are easily derived using addition theorems for trigonometric functions. A complex form of the shear modulus, G, can be used, as indicated in Fig. 4.160. 

Pak J, Wunderlich B (2002) Reversible Melting of Polyethylene Extended-chain Crystals Detected by Temperature-modulated Calorimetry. J Polymer Sci, Part B Polymer Phys 40 2219-2227. 

Chapter 4 Thermal Analysis Tools contains a detailed description of thermometry, calorimetry, temperature-modulated calorimetry (TMC), dilatometry, thermomechanical analysis (TMA), d)mamic mechanical analysis (DMA), and thermogravimetry (TGA). 

C. Schick and G.W.H. Hohne (Eds.), Special issue on temperature modulated calorimetry, Thermochimica Acta, 304/305 (1997). 

B. Wunderlich and 1. Okazaki, Temperature-Modulated Calorimetry of the Frequency Dependence of the Glass Transition of Poly(Ethylene Terephthalate) and Polystyrene. In M.R. Taut and A.l. Hhl, Eds. Structure and Properties of Glassy Polymers, ACS Symposium Series 710, Am. Chem. Soc., Washington, DC (1998) 103 116. 

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