Preparation of Large-scale Glycerol-based Organic Carbonates

Abstract

Polylactide (PLA; PLLA; Poly(L-lactide)) is a notable material derived from renewable sources and known for its biodegradability, though it requires specific industrial composting conditions. One significant drawback limiting PLA’s widespread use is its inherent brittleness, which causes it to fracture under minimal elongation despite its high tensile strength. A common solution to this issue is to blend PLA with plasticizers. In this study, a range of organic carbonates—namely, ethyl glycerol dicarbonate (1), methyl glycerol dicarbonate (2), glycerol carbonate (3), and acetyl glycerol carbonate (4)—were synthesized on a preparative scale (approximately 100 g) using renewable glycerol and CO2-derived diethyl carbonate (DEC) or dimethyl carbonate (DMC). Remarkably, 1–4 demonstrated biodegradability within a week under ambient conditions, confirmed through soil exposure at 25 °C—outpacing the degradation rate of cellulose materials in comparison. Further analysis revealed that compound 1 was particularly effect as a PLA plasticizer. The compatibility of PLA with up to 30 phr (parts per hundred resin) of the synthesized organic carbonates was systematically evaluated using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and rotation rheometry. These blends exhibited significantly improved ductility, as evidenced by tensile property measurements. Particularly, the novel plasticizer ethyl glycerol carbonate (1) demonstrated superior performance compared to the conventional plasticizer acetyltributylcitrate (ATBC) in terms of maintaining morphological stability. Unlike PLA/ATBC blends, which experienced slow crystallization over time at ambient temperature, PLA/1 blends retained their amorphous structure, thereby preventing plasticizer migration. This was corroborated by DMA analyses of both aged and unaged specimens. Despite these advantages, biodegradation tests indicated that the inclusion of biodegradable organic carbonate plasticizers did not enhance the biodegradability of PLA. The PLA matrix in the blends remained largely unchanged after 6 months of exposure to ambient soil conditions at 25 °C. This study highlights the potential of organic carbonates as eco-friendly plasticizers for PLA, promoting the development of sustainable and biodegradable polymer systems.