Hardener Isomerism and Content of Dynamic Disulfide Bond Effect on Chemical Recycling of Epoxy Networks

Nowadays, there is an important concern in the scientific community related to the end-of-life products derived from polymeric matrix composites. In this regard, covalent adaptable networks and, more specifically, the disulfide bond-based ones are a promising approach to develop composite parts able to be dissolved in a specific solvent, thus regaining the continuous fiber reinforcement. In this work, the effect of hardener isomerism, using 2-aminophenyl disulfide (2-AFD) and 4-aminophenyl disulfide (4-AFD), and amine/epoxy ratio (1.0–1.2) was studied to optimize the chemical recycling capabilities at different temperatures. Results confirmed the need for using hardener excesses for dissolving these vitrimers. Networks based on 2-AFD were dissolved in considerably lower times than the 4-AFD ones, which is interesting since the latter one is quite more used for this purpose and currently way more expensive. In this context, a composite laminate, reinforced with six layers of carbon fiber fabric, was manufactured as the proof-of-concept.