Temperature gradient, differential scanning calorimetry

All temperatures mentioned are influenced by the methods of their measurement [ 1.711, e. g. very thin samples in a cryomicroscope, very small amounts of product (mg range) in an installation for differential scanning calorimetry (DSC) and some temperature gradients in the sample during the measurement of the electrical resistance (ER). Tg., Tc and Tr measured with pure substances can supply helpful information about the temperature range to... 

The relationship between observed enthalpy-volume relaxations and thermal treatment of slightly oriented industrial PVC films was investigated. Differential scanning calorimetry at 20 -C per minute and specific volume analysis (density gradient column) were used to study the effects of annealing near and below Tg. Nonlinear effects in the volume relaxation at relatively long times and temperatures close to the glass transition produce deviations in the specific heat curves at temperatures far above Tg in addition to the normal overshoot effects. 

The effect of the substantial sample temperature gradients on the measurement of specific heats by differential scanning calorimetry is slight if, as is usually the case, the specific heat varies only slowly with temperature. Then even though the temperature drop across a sample is large, the change in specific heat across it is small and, as a result, the heat absorbed per unit temperature increase is approximately the same for all infinitesimal slices of the sample taken parallel to the cup bottom. 

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