Non-equilibrium heat capacity of polytetrafluoroethylene at room temperature

TL;DR

This study uses ac-calorimetry to investigate the non-equilibrium heat capacity of polytetrafluoroethylene around its phase transition temperatures, revealing frequency-dependent thermodynamic behavior.

Contribution

It introduces a thermal modeling approach to extract the complex heat capacity of PTFE out of equilibrium at room temperature.

Findings

Frequency-dependent real and imaginary heat capacity parts observed.

Thermodynamic behavior characterized during phase transition.

Modeling enables analysis of non-equilibrium heat capacity.

Abstract

Polytetrafluoroethylene can be considered as a model for calorimetric studies of complex systems with thermodynamics transitions at ambient temperature. This polymer exhibits two phase transitions of different nature at 292 K and 303 K. We show that sensitive ac-calorimetry measurements allow us to study the thermodynamic behaviour of polytetrafluoroethylene when it is brought out of thermodynamic equilibrium. Thanks to the thermal modelisation of our calorimetric device, the frequency dependent complex heat capacity of this polymer is extracted. The temperature and frequency variations of the real and imaginary parts of the complex heat capacity are obtained when polytetrafluoroethylene undergoes its first-order structural phase transition at 292 K.