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47. Influence of DSC thermal lag on evaluation of crystallization kinetics

Author

Svoboda, Roman, Perez Maqueda, Luis, Podzemná, Veronika, Perejon, Antonio, Svoboda, Ondřej, Svoboda, Roman, Perez Maqueda, Luis, Podzemná, Veronika, Perejon, Antonio, and Svoboda, Ondřej

Abstract

Influence of added thermal resistance on crystallization kinetics, as measured by differential scanning calorimetry (DSC), of the Se70Te30 glass was studied. The increase of thermal resistance was achieved by adding polytetrafluorethylene discs of different thicknesses (up to 0.5 mm) in-between the DSC platform and the pan with sample. Increase of the thermal resistance led to an apparent decrease (by more than 30%) in the crystallization enthalpy. Significant change of model-free kinetics occurred: apparent activation energy E of the crystallization process decreased (by more than 20%) due to the DSC data being progressively shifted to higher temperatures with increasing heating rate. The model-based kinetics was changed only slightly; the DSC peaks retained their asymmetry and the choice of the appropriate model was not influenced by the added thermal resistance. The temperature shift caused by added thermal lag was modeled for the low-to-moderate heating rates., Pomocí diferenční skenovací kalorimetrie byl sledován vliv přidaného tepelného odporu na měřená kinetická data pro krystalizaci sklovitého Se70Te30.

Published
2021

48. Quantitative characterization of multicomponent polymers by sample-controlled thermal analysis

Author

Sanchez-Jimenez, Pedro E., Perez-Maqueda, Luis A., Crespo-Amoros, Jose E., Lopez, Juan, Perejon, Antonio, and Criado, Jose M.

Subjects
Polymers -- Identification and classification, Polymers -- Chemical properties, Thermal analysis -- Methods, Chemistry
Abstract

This paper explores the potential of sample-controlled thermal analysis (SCTA) in order to perform compositional analysis of multicomponent polymeric materials by means of thermogravimetric experiments. In SCTA experiments, the response of the sample to the temperature determines the evolution of the temperature by means of a feedback system; thus, what is controlled is not the temperature--time profile, as in conventional analysis, but rather the evolution of the reaction rate with time. The higher resolving power provided by the technique has been used for determining the composition of polymer blends composed of polyvinyl chloride (PVC) and different commercial plasticizers, a system where the individual components have very similar thermal stabilities, thereby rendering useless thermogravimetric experiments run under conventional conditions. Different SCTA procedures, such as constant rate thermal analysis (CRTA), which has received special attention, and high-resolution and stepwise isothermal analysis have been tested, and the results obtained have been compared with linear heating rate technique. It has been proven that CRTA can be used to effectively determine the exact composition of the blend. 10.1021/ac101651g

Published
2010

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