Creep Mechanics of Epoxy Vitrimer Materials

Epoxy materials are an indispensable class of polymers due to their excellent mechanical properties and high thermal resistance. However, traditional epoxy materials are typically non-recyclable and face issues with fatigue and creep. To combat the issue of recyclability, research interest is increasingly centered on epoxy vitrimer materials, which exhibit a dynamic covalent bond exchange reaction at high temperatures allowing for self-healing, recycling, and shape reprogramming. Herein, we discuss the creep mechanics of epoxy vitrimers; we postulate that gaining a fundamental understanding of what causes creep in vitrimers will garner advances in vitrimer creep resistance for future applications. Isothermal creep results demonstrate the presence of three distinct creep regimes: primary creep associated with polymer chain mobility, secondary creep associated with network rearrangement due to the dynamic covalent bond exchange reaction, and tertiary creep associated with errors in this reaction. We note at low temperatures (T ≪ Tv) and catalyst concentrations, vitrimers simply behave as a traditional epoxy material. In contrast, at high temperatures and catalyst concentrations, vitrimers exhibit significantly more creep with strong correlations to catalyst concentration, heating rate, and temperature, which are quantified in this work.