Differential scanning calorimetry process

Sturtevant, J.M. 1980. Differential scanning calorimetry processes involving proteins. In Bioenergetics and Thermodynamics Model Systems. A. Braibanti, editor. John Wiley Sons, New York, 391-396. 

The process known as transimidization has been employed to functionalize polyimide oligomers, which were subsequentiy used to produce polyimide—titania hybrids (59). This technique resulted in the successhil synthesis of transparent hybrids composed of 18, 37, and 54% titania. The effect of metal alkoxide quantity, as well as the oligomer molecular weight and cure temperature, were evaluated using differential scanning calorimetry (dsc), thermogravimetric analysis (tga) and saxs. 

Cure kinetics of thermosets are usually deterrnined by dsc (63,64). However, for phenohc resins, the information is limited to the early stages of the cure because of the volatiles associated with the process. For pressurized dsc ceUs, the upper limit on temperature is ca 170°C. Differential scanning calorimetry is also used to measure the kinetics and reaction enthalpies of hquid resins in coatings, adhesives, laminations, and foam. Software packages that interpret dsc scans in terms of the cure kinetics are supphed by instmment manufacturers. 

Crystallinity in ECH and ECH—EO finished products increases over time, and may be detected by x-ray analysis or differential scanning calorimetry. In synthesizing ECH—EO, the process is designed to maximize random monomer sequence and minimize crystallinity. The ECH—EO molecular ratio in these products ranges from approximately 3 1 to 1 1. 

The various terms appearing in these equations are self-evident. The differential heat release, dkidt, data are computed from differential scanning calorimetry (DSC). A typical DSC isotherm for a polyurethane reactive system appears in Fig. 11. Energetic composite processing is normally conducted under isothermal conditions so that Eq. (15) is more applicable. 

Strict control of the fusion process is imperative. In addition to thickness, hardness, continuity and adhesion checks, correct cure may be assessed by differential scanning calorimetry techniques, which are designed to measure any difference in the glass transition temperature of a laboratory-cured powder and the cured coating taken from the factory-coated pipe. 

Differential scanning calorimetry (DSC) experiments on the various dimeric carbocycles indicated that, depending on the length of the alkyl groups, thermal polymerization had occurred between 100 and 125°C as an abrupt, exothermic process. The narrow temperature range for each exotherm was suggestive of a chain reaction however, IR spectroscopy revealed the absence of acetylene functionalities in the polymerized material. Consequently, none of the substi-... 

A 100 Degree Rule was often used in the past throughout the chemical industry to assess whether an accident would occur. According to this rule, if the operating temperature of a process is 100 "C away from the nearest detectable exotherm observed in DSC (Differential Scanning Calorimetry) experiment the operation will not experience this thermal event. In such a case no more detailed information on hazards need be searched for. The 100°C degree rule is, however, often far from the safety margin The use of this rule was the reason of many accidents. 

Thermodynamic measurements such as heat of solution from solution calorimetry [11,12], heat of fusion from differential scanning calorimetry (DSC) [12], and entropy of processing, ASp [12]... 

Differential scanning calorimetry can also supply valuable information regarding solvate species, and it is particularly useful with respect to temperature and energetics of the desolvation process Two samples of the developmental compound L-706000-001T were shown to be chemically identical, and each contained two moles of water. The XRD powder patterns for the two samples were found to be quite different, demonstrating the existence of polymorphism... 

Probably the main weakness of DTA as a method of analysis remains the difficulty of linking the thermal changes shown on the thermogram, with the actual thermal processes taking place. It should be noted that data obtained by DTA are often similar to those available for differential scanning calorimetry. Indeed the two techniques overlap extensively and may be seen as complementary. A comparison of the two techniques is made at the end of the next section. 

Hatley, R. H. M. The effective use of differential scanning calorimetry in the optimisation of freeze-drying processes and formulations. Developments in Biological Standardization Vol. 74, p. 105-122. Acting Editors Joan C. May, F. Brown S. Karger AG, CH-4009 Basel (Switzerland), 1992... 

The advantages of the phthalonitrile process are compromised by the fact that phthalonitrile is not only much more costly than phthalic anhydride but also less easily available. In view of the intermediates which have been found so far, and in conjunction with a study of the thermal course of the reaction using differential scanning calorimetry a reaction mechanism has been proposed for the phthalonitrile route which may be visualized as follows [11] ... 

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