Vitrimer resins have been increasingly considered for circular materials design due to their dynamic covalent networks, yet end-of-life processes remain insufficiently established. In this work, sub-critical hydrothermal liquefaction (HTL) in water was investigated as a chemical recycling pathway for a disulfide-based vitrimer (VR-RD) formulated from EP600 Part A (epoxy), 4-aminophenyl disulfide, and a cardanol-based diluent (LITE 513DF). Batch experiments were performed in Parr autoclave reactor (Model 4560, 300 mL) at a resin-to-water mass ratio of 1:17 under nitrogen. A matrix of conditions was assessed at 310 °C and 340 °C for 35 and 60 minutes, with the 300 mL reactor stirred at 150 rpm. Product streams were separated into gas, aqueous, crude oil, and char; the crude oil was further fractionated by distillation into light, intermediate, and heavy cuts.

Effective depolymerization of the vitrimer network was observed across all runs. Lower temperature and shorter residence time favored liquid formation, whereas higher severity promoted secondary conversion. The most favorable liquid production was obtained at 310 °C for 35 minutes, yielding the highest crude fraction (43.5\% of feed) and a light cut of 11.1\%. At 310 °C for 60 minutes, a reduction in crude oil and an increase in gas were observed, consistent with over-cracking. At 340 °C, liquid yields were diminished and solid/gaseous products increased.

Characterization of products was used to elucidate depolymerization pathways and product quality. Gas chromatography–mass spectrometry (GC–MS) of the light fractions confirmed the presence of aniline, indicating recovery of moieties associated with the epoxy precursor; the 310 °C-60 minutes case exhibited the highest relative aniline abundance (≈44\% within the light fraction). Inductively coupled plasma–optical emission spectroscopy (ICP-OES) of aqueous phases indicated sulfate, consistent with disulfide bond cleavage, and measurable chloride, which displayed contrasting trends with time and temperature. Thermogravimetric analysis (TGA) showed that most chars and heavy fractions possessed reduced thermal stability compared with the parent VR-RD, whereas the char obtained at 310 °C for 60 minutes exhibited a comparable onset temperature, suggesting partial retention or restructuring of thermally stable motifs. The fractionation protocol defined light as <120 °C vapor, intermediate as 120–350 °C vapor (noted as largely lost during handling), and heavy as non-vaporized residue (>350 °C), providing a practical basis for subsequent compositional analysis.

Overall, sub-critical HTL in water was demonstrated as a viable option for chemical recycling of disulfide-based vitrimers. Process severity was shown to govern the balance between depolymerization and secondary conversion, with 310 °C for 35 minutes identified as optimal for maximizing desirable liquids while minimizing over-cracking. These findings provide actionable guidance for scale-up and for coupling HTL with targeted product upgrading.