Thermomechanical analysis (TMA) of vitrimers

Abstract

Vitrimers are an exciting class and new generation of polymer materials combining the strength of a traditional thermoset polymer with the reprocessability of a traditional thermoplastic polymer. However, a key debate in literature has surrounded the best method to identify the vitrimer topology freezing temperature (Tv), above which dynamic covalent bond exchange reactions occur, allowing for self-healing, recycling, and shape reconfigurability of vitrimers. While common methods in literature to identify the Tv include stress relaxation, creep, and fluorescence, we herein validate thermomechanical analysis (TMA) as a reliable method for Tv identification. TMA provides several clear advantages as it is less time and sample intensive than stress relaxation. Furthermore, it is performed in compression to match application conditions, provides more consistent results than creep, and identifies the coefficient of thermal expansion (α). We demonstrate that expansion TMA is a valuable tool in Tv identification by validating several clearly accepted trends in literature; TMA validates that the Tv increases with decreasing catalyst concentration and increasing heating rate while showing negligible variation with increasing applied force. Finally, we report an increasing α with increasing catalyst concentration for our vitrimer material. By taking advantage of such a fast and reliable method to identify Tv, we believe this fundamental study will support future vitrimer research.