Differential scanning calorimetry enthalpy change

Penetrant-Induced Effects. History-dependent properties of glassy polymers are well documented in terms of thermal (113,114) and mechanical U15) properties. Studies have related excess enthalpy changes measured by differential scanning calorimetry to changes in small-molecule sorption (116,117). Many studies have reported penetrant-induced history-dependent (or conditioning) effects for gas and vapor sorption and transport properties in glassy... 

Although there are other ways, one of the most convenient and rapid ways to measure AH is by differential scanning calorimetry. When the temperature is reached at which a phase transition occurs, heat is absorbed, so more heat must flow to the sample in order to keep the temperature equal to that of the reference. This produces a peak in the endothermic direction. If the transition is readily reversible, cooling the sample will result in heat being liberated as the sample is transformed into the original phase, and a peak in the exothermic direction will be observed. The area of the peak is proportional to the enthalpy change for transformation of the sample into the new phase. Before the sample is completely transformed into the new phase, the fraction transformed at a specific temperature can be determined by comparing the partial peak area up to that temperature to the total area. That fraction, a, determined as a function of temperature can be used as the variable for kinetic analysis of the transformation. 

Differential scanning calorimetry has been used88 to measure the enthalpy change, AH0 for the exothermic decarbonylation reaction... 

Differential scanning calorimetry (DSC) was designed to obtain the enthalpy or the internal energy of those processes and also to measure temperature-dependent properties of substances, such as the heat capacity. This is done by monitoring the change of the difference between the heat flow rate or power to a sample (S) and to a reference material (R), A

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Differential scanning calorimetry (DSC) Since lc s form phases in a thermodynamic sense, a transition from one phase to another is accompanied by a phase-transition enthalpy. Nevertheless, there are phase transitions of second-order character which can hardly be detected by DSC since there is no phase-transition enthalpy but just a change in heat capacity. A typical example is the transition from orthogonal phases to tilted phases. 

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. ... 

Gospodinov and Bogdanov [84GOS/BOG] report the total enthalpy change of the reaction CuSe03(cr) CuO(cr) + Se02(g) from a measurement by differential scanning calorimetry (DSC) to be 36 kJ-mol, which is an improbably low value. 

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