Fast-scan DSC

The quantitative data, curve shapes, and breadth of melting at 200°C/min are in satisfactory agreement with the thermal properties established earlier by the slow adiabatic calorimetry (AC) measurements. The exception is the 

The data in Fig. 2.84 indicate that an amorphous polycarbonate sample as small as 50 pg could be heated at 400 C/min and yield a glass transition that is as discernible as that shown in Fig. 2.84 for the 1-mg sample of polycarbonate scanned at 20 C/min. These results indicate that it is now possible to determine thermal properties on polymeric samples that were previously deemed too small to analyze. 

Pijpers et al. (2002) have shown the utility of using fast scan rates to prevent crystallization of poly(ethylene terephthalate) (PET). In Fig. 2.85 during cooling at 100°C/min, no crystallization occurs, only vitrification. On reheating PET at 10°C/min, devitrification is observed, followed by extensive cold crystallization near 150 C. This is followed by melting at 23( -260°C. However, on the first heating of PET at lOO C/min, cold crystallization is nearly eliminated and the subsequent melting is quite small. 

In conclusion, it can be said that if the sample size is reduced and a single sheet of thin aluminum foil is used to encapsulate the sample, it is possible to obtain good-quality data in a power compensation DSC at rates up to 500 C/min. 

High scan rates obviously enable measurement times to be reduced dramatically. With these fast DSC rates the thermal behavior of polymeric materials can be studied quantitatively as well as qualitatively. With fast scan rates 

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Potential applications of thermal analysis and calorimetry to quality control is not limited in any way to those discussed in this chapter. Once some physical or chemical characteristic of a material or process is known and can be examined and/or characterized by these techniques, it is only the imagination that limits the possibilities for quality control applications. Both traditional techniques (DSC, TG, DMA, isothermal calorimetry, etc.) and non-traditional techniques (temperature modeling, etc.) have been shown to have potential uses for quality control. With the introduction of many new techniques (fast scanning DSC, sample controlled thermal analysis (SCTA), modulated and other temperature programmed techniques, etc.), many more new opportunities will arise for providing quality control tools. 

J.L. Ford, T.E. Mann, Fast-Scan DSC and its role in pharmaceutical physical form characterisation and selection, Adv. Drug Deliv. Rev. 64 (5) (2012) 422-430. 

Ford JL, Mann TE (2012) Fast-scan DSC and its role in pharmaceuticed physical form chtiracteri-sation and selection. Adv Drug DeUv Rev 64 422-430 Forster A, Apperley D, HempenstaU J, Lancaster R, Rades T (2003) Investigation of the physical stability of amorphous drug and dmg/polymer melts using variable temperature solid state NMR. 

Fig. 2.1 Hoffman-Weeks plot for polyethylene crystallized in a fast DSC. The symbol open circle represents melting by fast scan DSC after isothermal crystallization, filled circle represents melting after a constant cooling rate and filled diamond represents the melting of a conventional DSC after isothermal crystallization. The solid black line plots Tm — T c (Part of Figure 6 reprinted from Polymer, 55(14), 3186-3194 Toda et al. Copyright 2014 with permission from Elsevier)...

Most pans can be used as received but sometimes a batch may be found to be slightly contaminated, possibly with a trace of machine oils used in pan manufacture. If so, pans can be cleaned by volatilising off the oil. Heating to 300 °C should be more than adequate for this. If using a hot plate, do not heat a lot of pans all together or they may stick together. The use of clean pans is also important for very sensitive work with fast scan DSC. 

Figure 1.16 The heat capacity trace of PET cooling at 200°C/min using fast scan DSC. The Tg is clearly shown as a step similar to that found on heating.

The small furnaces of this system can be heated or cooled at very low rates to very high rates and are ideal for a range of different techniques, particularly fast scan DSC. Power-compensated DSC also permits true isothermal operation, since under constant temperature conditions both the sample and furnace are held isothermaUy. The temperature range of... 

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