PLA-Based Green Antimicrobial and Flame-Retardant Biocomposites Reinforced with Sida hermaphrodita Fibers

Enhanced demand for the development of sustainable materials has generated significant research interest in products containing biomass-derived fibers, such as the fibers extracted from the energy crop Sida hermaphrodita (SH). Green chemicals and green methods, such as microwave treatment, have been used for the isolation of fibers from biomass waste. In this study, long extracted fibers were used as a reinforcement of the PLA matrix to give them high strength, which is required for high-performance biocomposites. To enable composite usage in automotive industry, several additives were applied to enhance their mechanical, thermal, and antimicrobial properties. Therefore, vegetable drying oil, montmorillonite nanoclay (MMT), and milled cork were used to improve their mechanical and thermal properties. Zinc oxide (ZnO) was applied to enhance the biocomposite’s antimicrobial properties, which were confirmed through significant bacterial reduction across all tested biocomposite variants, particularly in samples functionalized with ZnO, cork, and montmorillonite. Additionally, X-ray microtomography provided detailed insight into fiber dispersion and internal structural heterogeneity, which is crucial for evaluating mechanical performance and flame-retardant behavior. All characterization methods, including mechanical ones, lead to the conclusion that green and sustainable biocomposites based on PLA and Sida hermaphrodita fibers treated with antimicrobial (AM) and flame-retardant (FR) agents can be successfully applied for a wide variety of antimicrobial and flame-retardant products.