Lignin was chemically modified via acetylation to enhance its compatibility with polylactic acid (PLA) and the properties of resulting biocomposites. A microwave-assisted method was used to optimise the acetylation process by notably reducing its time and increasing its efficiency. Acetylation enhanced the interfacial adhesion between lignin and PLA, notably improving the mechanical, thermal, and moisture-repellent properties of the corresponding composites. The incorporation of Biomax® Strong as an impact modifier further increased ductility and impact strength, with blends containing 15–20 wt.% lignin and 5 wt.% impact modifier featuring a higher impact strength than those with lignin only.
Building on these advancements, the development of fibre-reinforced composites was explored by combining PLA, microwave-acetylated lignin, and regenerated cellulosic fibres. Fibre inclusion provided an additional reinforcement, resulting in composites with a higher tensile strength, impact resistance, and thermal stability. Thus, microwave-assisted lignin modification combined with fibre reinforcement was identified as an efficient and sustainable route to lightweight high-performance materials showing potential for eco-friendly applications in the automotive and industrial sectors.
By utilising lignin, a low-cost byproduct off the pulping industry, this study highlights an innovative strategy for transforming a traditionally underutilised material into a valuable resource for high-performance biocomposites. The successful integration of chemically modified lignin into PLA-based materials not only enhances their mechanical strength, impact resistance, and thermal stability, but also contributes to the advancement of sustainable manufacturing. By repurposing lignin, this research underscores its potential to play a key role in reducing the dependence on fossil-based materials, promotes circular economy principles, and enables the development of lightweight, durable, and eco–friendly composites for next-generation applications.