Endothermic process differential scanning calorimetry

The thermal unfolding of proteins is best measured by differential scanning calorimetry, which measures the heat absorbed by a protein as it is slowly heated through its melting transition (Figure 17.1). A solution of about 1 mg of protein in 1 mL of buffer and a separate reference sample of buffer alone are heated electrically.6 The additional current required to heat the protein solution is recorded. As the protein denatures, there is a large uptake of heat because the process is highly endothermic. The temperature at the maximum of the peak is... 

Differential Scanning Calorimetry. A Perkin-Elmer Model DSC-IB calorimeter was used to examine crystallinity by measuring areas under the fusion curve as a function of elastomer composition and processing variables. Areas of endotherms were calibrated against an indium standard and the crystallinity calculated using a value of —138 J/g for a 100% crystalline polypropylene polymer (II). 

Differential scanning calorimetry (DSC) can be used to determine experimentally the glass transition temperature. The glass transition process is illustrated in Fig. 1.5b for a glassy polymer which does not crystallize and is being slowly heated from a temperature below Tg. Here, the drop which is marked Tg at its midpoint, represents the increase in energy which is supplied to the sample to maintain it at the same temperature as the reference material. This is necessary due to the relatively rapid increase in the heat capacity of the sample as its temperature is increases pass Tg. The addition of heat energy corresponds to the endothermal direction. 

Differential thermal analysis (DTA) measures the amount of heat released or absorbed by a sample as it is heated at a known rate." When the enthalpy change is determined, the method is called differential scanning calorimetry (DSC). The presence of exothermic or endothermic processes at certain temperatnres provides information about the nature of phase changes and chemical reactions occurring in the material as it is heated. DTA can often be used as a sensitive method for establishing the presence or absence of secondary phases in samples if these phases undergo phase transformations at known temperatures. ... 

From the similarities in chemical architecture of these two polymers, as well as from their similar processing histories, some degree of morphological equivalence is expected. Both polymers possess two-phase morphologies as demonstrated by differential scanning calorimetry (DSC). At sub-ambient temperatures the DSC spectra show glass transitions, thought to be soft-phase phenomena. Above room temperature both systems demonstrate endothermic processes related to disruption of hard phases. These events are summarized in Table 1. 

Differential scanning calorimetry (DSC) curves of levofloxacin hemihydrate measured under various conditions showed different thermograms. This behavior was attributed to the dehydration process that resulted in a multiple-phase transition. Dehydration at higher temperatures (above 70° C) gave a sharp endothermic peak in the DSC thermogram due to the melting of the y-form, and at a lower temperature (50°C) it led to the observation of a sharp endothermic peak due to the... 

The gelatinization process can be observed by the differential scanning calorimetry (DSC) technique. Depending on the amount of water present in the system, several endotherm peaks can be detected (Figure 2.2). If the water volume fraction is significantly above 0.45 (conditions that can be referred to gelatinization) a single endotherm peak, pointed as G is observed [11]. 

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