High-Speed Calorimetry for the Study of the Kinetics of (De)vitrification, Crystallization, and Melting of Macromolecules

Abstract

This paper reports on the characteristics and use of a new mode of measurement: High Performance DSC (HPer DSC), which represents a major step forward in high-speed calorimetry, as compared to standard DSC. It facilitates the study of the kinetics and metastability of macromolecular systems, especially the analysis of rate-dependent phenomena in real time. Controlled and constant scan rates at hundreds of degrees per minute and combinations thereof both in cooling and in heating are possible. Heats of transition, heat capacities, temperature-dependent crystallinities, etc. can be established at the extreme rates applied. Examples of the utilization of HPer DSC are given for polymers with respect to the effective hindrance of crystallization and cold crystallization, avoidance of recrystallization and the rate dependency of vitrification and devitrification. Low, milligram-scale sample masses, even down to the microgram level, are utilized. The short measuring times also provide the high throughput needed in combinatorial chemistry.

Evidence of transformation bursts during thermal cycling of a Pu-Ga alloy

“…The purge gas was a mix of 90%Ne/10%He, which can be used between -176°C and 585°C. 16 In the DSC thermal cycling experiments described here, the sample was cooled from 25°C to -160°C, held for 1 minute, heated to 350°C, held for 1 minute, and then cooled back to 25°C. Heating and cooling rates were between 1.5 and 20°C/min.…”

Methodology for DSC calibration i nhigh heating rates

“…Another approach is related to sample pans, which can be made of different material types (copper, aluminum, stainless steel, platinum, gold, glass and others) and can change the sample pan thermal conductivity, the heat capacity or the thermal diffusivity during the experiments, which modify the heat transmission in the sample direction and, consequently, the final DSC curve shape. Table 4 -Experimental values for 10.2mg indium sample and the calibration was carried out at 100°C.min -1 , both, calibration and experiments carried out into aluminum foil sample pan According to Pijpers et al (2002), in order to minimize the thermal gradient inside the sample, when the sample heating rate be increased of a "z" factor, the sample mass should be reduced by the same factor "z" (Pijpers, 2002;Pijpers, 2004).…”

“…Considering to the use of DSC technique in high heat rates, as showed previously, the literature presents some little works in the pharmaceutical area (Gramaglia et al, 2005;Hurtta and Pitkänen, 2004;McGregor et al, 2004;Saunders et al, 2004) and in the characterization of polymer processing in real time (Poel and Mathot, 2006;Gill and Sauerbrunn, 1993;Pijpers et al, 2000;Pijpers et al, 2004;Pijpers et al, 2002). These studies, despite of being rare, show the good potential of this technique in the study of material thermal behavior.…”

A scanning AC calorimetry technique for the analysis of nano-scale quantities of materials

“…1 The ability to perform calorimetry measurements at very fast scan rates is interesting also, as it enables the study of metastable phases and more generally of materials far from equilibrium. [2][3][4][5][6] Thus, a scanning calorimetry technique that can operate over a broad range of heating and cooling rates is an attractive and powerful tool for materials researchers.…”