Every year, huge amounts of natural waste are produced by various industries. In the current raw materials crisis, particular attention should be paid to the possibility of reusing them instead of disposing of them. After appropriate processing of natural raw materials, e.g., through alkalization or the addition of modifiers, they can be successfully used as fillers for plastics. Adding them to bio-based polylactide enables the production of composites with new properties that are also environmentally friendly.
In this study, several plant-based wastes were selected as fillers: straw, grass, reed, sunflower husk, as well as raspberry, evening primrose, and milk thistle pomaces. The raw materials were subjected to grinding, alkalization, and rinsing to neutralize the pH. Before further processing, the fibers were dried to remove residual solvents and moisture.
Concentrates with 20 wt% filler content were obtained by mixing PLA with the plant-based fillers in the molten state. The resulting materials were crushed using a knife granulator, and the granules were processed via injection molding. Ultimately, samples containing 5, 10, and 20 wt% of filler were produced.
To characterize the PLA composites, melt flow index (MFI) measurements, FT-IR spectroscopy, thermal analysis, and mechanical tests (tensile and flexural strength and impact strength) were performed. The results allow the assessment of flowability, processing behavior, and the basic mechanical and structural properties of the obtained composites. In this work, particular emphasis is placed on the properties of composites containing grass filler.

Research conducted under the project M-ERA.NET 3 call 2022 “Multifunctional materials based on polylactide” No. M-ERA.NET3/2022/73/PolyBioMat/2023 funded by the National Center for Research and Development.