Upcycling Polylactide into UV-Curable Pressure-Sensitive Adhesives via Glycolysis and Maleic Anhydride Functionalization

Open-loop recycling can valorize polylactide (PLA) when mechanical recycling or industrial composting is impractical. This study links PLA glycolysis modeling to UV-curable pressure-sensitive adhesive (PSA) development. A six-reaction transesterification model was calibrated against published data and used to select glycolysis conditions: 120 min at 220 °C and a PLA-repeat-unit:glycerol molar ratio of 1:0.25. Model–experiment discrepancies were 0.2% for hydroxyl value, 10.9% for apparent number-average molar mass, and 3.3% for apparent weight-average molar mass, indicating agreement with the calibration dataset. Oligomers were partially esterified with maleic anhydride (MA; nominal OH:MA ratios of 1:0.2–1:0.7) under ATR-FTIR monitoring and UV-cured at 365 nm with 10–40 wt.% 2-hydroxyethyl acrylate (HEA) on precursor mass. Tack and T-peel resistance increased with HEA loading, whereas apparent lap-shear strength showed precursor-dependent trends, including intermediate-loading maxima. A formulation with OH:MA = 1:0.5 and 30 parts HEA combined an apparent lap-shear strength of 0.30 MPa, T-peel resistance of 0.20 N/mm, and loop-tack force of 9.6 N/25 mm. These findings support glycolysis-derived PLA oligomers as tunable, partially biobased, PSA precursors.