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This work describes the composition of the products from solvolysis of thermoset polyester in an acetone/water mixture. A qualitative and quantitative evaluation of the compositions of the aqueous and oil phases was achieved by the combination of liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS/MS), gel permeation chromatography (GPC), and total organic carbon (TOC). Close to 100% of the organic carbon in the aqueous phase was explained by the monomers phthalic acid and dipropylene glycol, co-solvent acetone, and a secondary reaction product, isophorone. In the oil, the most abundant compounds were isophorone, 3,3,6,8-tetramethyl-1-tetralone, and dihydroisophorone. While the first two compounds were intermediates in the self-condensation of acetone, dihydroisophorone has not been reported previously as the by-product of the conventional acetone self-condensation reaction pathway. The quantification results have shown that solvolysis can be successfully used to close the loop in the polymer life cycle while producing a broad spectrum of high-value products that could be recycled for production of polymers, used as a building blocks, or as fine chemicals.