Solvolysis depolymerization of additive-containing poly(lactic acid) composites for sustainable ethyl lactate production

Abstract

The increasing use of poly(lactic acid) materials has led to growing amounts of post-consumer waste containing commonly used industrial additives that complicate end-of-life treatment. Although solvolysis represents a promising chemical recycling route for PLA, systematic comparative data quantifying the influence of common additives under relatively mild reaction conditions remain scarce. This study investigates the solvolysis depolymerization of PLA-based composites containing typical additives, including calcium carbonate (1–10 wt%), carbon black, plasticizers, cellulose, and minor polymeric components. Depolymerization was performed in an acetone/ethanol system at 70 °C using the organocatalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene, enabling recovery of ethyl lactate as a bio-based solvent. Depolymerization efficiencies ranged from 61-100 %, depending on additive form and content. High efficiencies and PLA conversion to ethyl lactate (up to 98%) were obtained for materials containing low amounts of inorganic additives (≤2 wt%), whereas cellulose-rich composites showed markedly reduced degradation and product formation. The results demonstrate that additive form and content govern depolymerization performance more strongly than crystallinity effects alone, with cellulose-rich matrices (>50 wt%) defining a practical compositional threshold for efficient chemical recycling. Structural and thermal analyses (GPC, DSC, TGA, and XRD) indicated that additives increased crystallinity and thermal stability while solvolysis remained effective at low to moderate additive loadings. This work extends solvolysis recycling strategies from virgin PLA to commercially relevant composite materials and defines compositional limits for efficient ethyl lactate production from additive-containing PLA waste.