Sustainable Waterborne Polylactide Coatings Enabled by Ionic Liquid Plasticization

This work presents an approach to water-dispersible polylactide (PLA) particle fabrication and their application in low-temperature film formation using a combination of mechanical dispersion and ultrasonication techniques. Stable PLA dispersions were obtained after removal of surfactant and allowed for the preparation of thin films exhibiting significantly reduced minimum film-formation temperature (MFFT), particularly when plasticized. To tailor the interfacial behavior and mechanical flexibility of the resulting coatings, a set of conventional and bio-based plasticizers was evaluated, including epoxidized fatty acids, PEG-400, and several hydrophobic deep eutectic solvents (HDES) synthesized from menthol and carboxylic acids. Compatibility between PLA and each plasticizer was predicted using Hansen solubility parameters, and the efficiency of plasticization was assessed through glass-transition temperature suppression in solvent-cast films. The combination of submicron PLA particles and selected plasticizers enabled film formation at temperatures as low as 48 °C, confirming the potential of these systems for energy-efficient coating technologies. Furthermore, composite coatings incorporating micro sized cellulose fibers regenerated from agricultural residues were successfully obtained, demonstrating the feasibility of integrating bio-derived fillers into waterborne PLA formulations. This study highlights the use of water-insoluble ionic-liquid-type plasticizers for PLA dispersions and establishes a foundation for developing sustainable, low-VOC, and low-temperature PLA-based coating materials.