Processability and reprocessability maps for vitrimers considering thermal degradation and thermal gradients

Abstract

A lack of fundamental knowledge about the kinetic mechanisms governing the processing and reprocessing of vitrimers forces a trial-and-error procedure to be adopted when choosing treatment conditions. In this work, we develop diagrams to be used as a straightforward tool to decide the curing and thermoforming parameters of vitrimers. The thermal stability of a disulfide containing epoxy has been evaluated by means of thermal analysis methods. By characterizing the kinetics of the curing and decomposition of the resin through a model-free kinetic method, we have been able to generate an intuitive processability map based on Time-Temperature-Transformation plots. The resulting chart allows for the optimum curing conditions that will avoid degradation to be identified. A similar chart for reprocessability has been obtained by considering the exchange kinetics of the characteristic stress relaxation behavior of vitrimers. Furthermore, we have incorporated into the diagrams criteria to determine the critical thickness below which a tolerable thermal gradient is not exceeded. Our diagrams have been experimentally validated, thus proving to be a useful and valid tool for rapid decision-making situations.