Toward sustainable polymer composites: Synergetic effects of surface-treated <i>Mimusops elengi</i> seed shell powder on polypropylene properties

The increased demand for non-renewable, petroleum-based plastics and their negative impacts on human and environmental sustainability has led researchers to develop bio-composites to make eco-friendly materials from renewable and natural resources. These materials minimize plastic manufacturing carbon footprints while performing well. In this study, NaOH treatment of Mimusops elengi seed shell powder (MESSP) affects density, chemical functionality and composition, surface shape, and thermal degradation. It also examines the properties of polypropylene (PP) composites incorporating untreated and NaOH-treated MESSP, with sodium hydroxide concentrations ranging from 5 to 8 wt%. A series of PP composites containing untreated and NaOH-treated MESSP, with filler loadings varied between 0 and 20 wt%, was produced via melt mixing method in an internal mixer. MESSP particle treatment with 5 wt% NaOH effectively enhanced the chemical functionality, cellulose content, and particle morphology as confirmed through FTIR and SEM analysis. The treatment of MESSP resulted in a noticeable reduction of hydroxyl (OH) functional groups, confirming a decrease in its hydrophilicity. Morphological analysis revealed increased porosity in the treated MESSP and improved adhesion of the PP matrix to MESSP. At 15 wt% loading (optimum), PP/TMESSP composite exhibited 30% and 28% enhancement in tensile strength and impact strength, respectively compared with PP/MESSP composite. Since they absorbed less water than PP/MESSP composites, PP/TMESSP composites had superior water absorption resistance. This study could lead to eco-friendly polymeric materials for packaging, automobile, and construction.