Lignin‐Polylactic Acid Biopolymer Blends for Advanced Applications – Effects of Microwave‐Assisted Acetylation of Lignin

ABSTRACT

In this study, the effects of microwave‐assisted acetylation of lignin on the properties of lignin/poly (lactic acid) (PLA) biocomposites have been developed and investigated. Acetylation was selected to reduce the hydrophilicity of lignin and improve its compatibility and dispersion within the hydrophobic PLA matrix. Microwave irradiation was employed as an alternative to conventional acetylation, providing a substantially shorter active treatment period without the use of a catalyst. The modified lignin was then blended with PLA and Biomax® Strong SG 120, an impact modifier, to produce biopolymer blends. The characterisation of the acetylated lignin was performed using Nuclear Magnetic Resonance (NMR) and Attenuated Total Reflectance Fourier‐Transform Infrared (ATR‐FTIR) spectroscopy, which confirmed successful modification through the appearance of ester signals and reduction of hydroxyl groups. Tensile and impact tests, conducted in accordance with ISO standards, demonstrated that the addition of acetylated lignin and the impact modifier improved the properties of the modified PLA‐lignin blends, increasing impact strength, ductility and thermal stability. These findings suggest that microwave‐assisted acetylation of lignin is a viable method to enhance the compatibility of lignin with PLA, leading to biopolymer blends with enhanced mechanical and thermal properties. This study further highlights the potential of these sustainable, high‐performance materials for a range of advanced applications, promoting the use of renewable resources in the development of eco‐friendly biopolymer blends and composites.