Temperature Modulated DSC TMDSC

A variation on the standard temperature programmes used in TA has recently been introduced [2-6]. This technique can in principle be applied to quantitative 

DTA as well as power compensation DSC instruments, and is called temperature modulated DSC, or TMDSC. The following trade marks are used by different TA instrument manufacturers for their temperature modulated differential scanning calorimeters Modulated DSC (MDSC ) of TA Instruments Inc., Oscillating DSC (ODSC ) of Seiko Instruments Inc., Alternating DSC (ADSC ) of Mettler-Toledo Inc. and Dynamic DSC (DDSC ) of Perkin-Elmer Corp. 

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Pyda and co-workers [49, 60] measured the reversible and irreversible PTT heat capacity, Cp, using adiabatic calorimetry, DSC and temperature-modulated DSC (TMDSC), and compared the experimental Cp values to those calculated from the Tarasov equation by using polymer chain skeletal vibration contributions (Figure 11.7). The measured and calculated heat capacities agreed with each other to within < 3 % standard deviation. The A Cp values for fully crystalline and amorphous PTT are 88.8 and 94J/Kmol, respectively. 

Temperature modulated DSC (TMDSC) is an advanced DSC technique in which the heating rate is modulated by superimposing a cyclic heating rate on the constant rate for example, a sinusoidal temperature modulation is superimposed on the temperature profile. 

Figure 10.6 Schematic temperature modulated DSC (TMDSC) curves for a polymeric sample. (Reproduced with permission from T. Hatakeyama and F.X. Quinn, Thermal Analysis Fundamentals and Applications to Polymer Science, 2nd ed., John Wiley Sons Ltd, Chichester. 1999 John Wiley Sons Ltd.)...

Thermal analysis techniques have had only limited use in the study of the various dental materials used for restorative, prosthetic and implant applications. The innovative research by Brantley s group, using conventional and temperature-modulated DSC (TMDSC) to examine the thermal behaviour of several metallic and polymeric dental materials, is described in Chapter 17 and numerous matters requiring additional research are identified. 

In 2001, Simon reviewed the theory of temperature-modulated DSC (TMDSC) with several examples of its applications, including many inorganic and coordination compounds [8]. Starink [9] provided a comprehensive review of the application of calorimetry in the analysis of a large variety of processes in aluminum-based alloys. 

A wide variety of dental materials is used in the oral environment for restorative, prosthetic and implant applications, and these materials are described at length in textbooks [1-3]. While their physical and mechanical properties have been studied extensively, there has been relatively little use of thermal analysis techniques to gain insight into dental materials. Our group has performed extensive research on several metallic and polymeric dental materials, principally utilizing conventional DSC and temperature-modulated DSC (TMDSC). These studies and thermal analysis studies of dental materials by other research groups are reviewed in this chapter. Although much novel information has been provided, numerous matters are discussed that require additional research. 

In the more recently developed temperature-modulated DSC (TMDSC, see Sect. 4.4 [11]), a sinusoidal or other periodic change in temperature is superimposed on the underlying heating rate. The heat capacity is now given by the bottom equation in Fig. 2.28, where and A are the maximum amplitudes of the modulation found in temperature difference and sample temperature, respectively, and co is the modulation frequency 27i/period. The equation represents the reversing heat capacity. In case there is a difference between the result of the last two equations, this is called a nonreversing heat capacity, and is connected to processes within the sample which are slower than the addition of the heat or which cannot be modulated at all (such as irreversible crystallization and reorganization, or heat losses). 

Schick C, Wurm A, Merzlyakov M, Minakov A, Marand H (2001) Crystallization and Melting of Polycarbonate Studied by Temperature-modulated DSC (TMDSC). J Thermal Anal Cal 64 549-555. 

A good example of the above statement are experiments with temperature-modulated dsc (TMDSC) on samples of hnear PE (112). Here a programmable temperature controller is set up in such a way that the temperature/time profile follows exactly the profile that in an off-line modulated dsc instrument is applied to the sample. By carefully assessing the correlation between the temperature profile and the influence this exerts on the invariant Q, as well as on the ciystalhnity derived from the waxs, it is possible to show that reversible melting and crystallization take place at the lamellar fold surface and not on the lateral surfaces of the crystallites (see Figs. 26a and 26b). 

In order to compare the model calculations with experimental calorimetric data, PS samples were modified in a transitiometer used, in this case, as a small reactor to modify PS under equilibrium conditions in the presence of a chosen fluid. Modifications of PS have been done in the presence of N2 and CO2, along isotherms at a given pressure. For these two fluids, a final temperature of 398.15 K and a final pressure of 80 MPa have been attained. The Tg of modified and nonmodified PS samples were determined by temperature-modulated DSC (TMDSC). The solubilities of the different gases were measured using the YW-pVT sorption technique [48, 49] along different isotherms, and the mass fraction of the gas in the polymer was then determined with the following equation ... 

In the case of PHB/high molar mass PLLA mixtures, the presence of separated peaks of cold crystallization on the DSC trace disallowed Tg to be read. Hence, Tg blends was studied by temperature modulated DSC (TMDSC). 

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