Origin of the broad endothermic peak observed at low temperatures for polystyrene and metals in Flash differential scanning calorimetry

Date

2022

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Abstract

The glass transition behavior of polystyrene as a function of different cooling rates with scanning to two different end temperatures, 30°C and −80°C, was investigated for four different substrate conditions using Flash differential scanning calorimetry, a fast scanning nanocalorimetry technique. In addition, structural recovery of polystyrene was performed at 20°C for aging times from 0.01 s to 8 h with scanning to −80°C for the same samples. A broad endotherm appears to grow at low temperatures (T << Tg) as cooling rate decreases and aging time increases, which is influenced by the substrate underlying the film, as well as by the end temperature condition in the scanning experiment. On the other hand, the endothermic overshoot associated with Tg is not influenced by substrate or scan end temperature. In addition, indium and vapor-deposited gold, both crystalline materials, show the growth of a very similar broad endotherm at low temperatures as cooling rate decreases and aging time increases indicating that the low-temperature endotherm is an artifact and not a relaxation associated with the material under investigation. Several potential explanations are put forward.

Description

© 2022 The Authors. Polymer Engineering & Science published by Wiley Periodicals LLC on behalf of Society of Plastics Engineers. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Keywords

Calorimetry, Glass Transition, Polystyrene

Citation

Pallaka, M. R., Bari, R., Simon, S. L., Polym. Eng. Sci. 2022, 62( 9), 3059. https://doi.org/10.1002/pen.26102

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