Utilizing foxtail millet husk waste for sustainable new bioplastic composites with enhanced thermal stability and biodegradability

Abstract

Foxtail millet husk (FMH) is a byproduct that is not suitable for consumption and is often discarded as solid waste. However, it can be used as a raw material to develop novel bioplastic composites that transform agro-based leftovers into value-added goods. Herein, new bioplastic composites were developed from poly(lactic acid), poly(butylene adipate-co-terephthalate) and FMH based granules by Injection Molding. The required granules were generated via a solvent evaporation method. The resulted bioplastic composites were analyzed for their morphologies, mechanical properties, crystal structures, thermal stability, and melting and crystallization behaviors using various techniques, such as scanning electron microscopy, universal testing machine, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. Expressly, chemical bonding between FMH fibers and poly(lactic acid)/poly(butylene adipate-co-terephthalate) PLA/PBAT was confirmed through Fourier Transform infrared spectroscopy analysis. The inclusion of FMH lowered the impact strength of the PLA/PBAT combination, which was confirmed by mechanical analysis. Morphological findings confirmed that the PLA/PBAT combination had FMH aggregation. DSC thermograph revealed negligible differences in glass transition and melting temperatures of PLA/PBAT blend with and without FMH. The thermogravimetry results exhibit that the FMH can improve bioplastic thermal stability. The addition of FMH improved the biodegradability of the PLA/PBAT bioplastic composites. Overall, FMH waste can be repurposed for bioplastic composites with enhanced thermal stability and biodegradability. This reduces solid waste from agricultural practices and creates eco-friendly products. Further research could lead to more sustainable alternatives.