Investigation of Mechanical, Thermal, and Morphological Properties of Palm and Tamarind Fiber Reinforced Hybrid Polypropylene Composites: Effect of Fiber Loading, Fiber Ratio, and Alkali Treatment

ABSTRACT This study investigates hybrid polypropylene (PP) composites reinforced with palm ( Borassus flabellifer ) leaf‐sheath fiber and tamarind ( Tamarindus indica ) fruit‐shell fiber. The effects of fiber loading (5, 10, and 15 wt%), palm:tamarind fiber ratio (1:1, 2:1, and 1:2), and alkali treatment were evaluated. The composites were fabricated by hot‐press compression molding and characterized through tensile, flexural, impact, hardness, water absorption, FTIR, thermogravimetric analysis, and scanning electron microscopy. Increasing fiber loading generally increased hardness and water absorption, while tensile strength decreased with increasing fiber content. The highest tensile strength among untreated composites was 16.42 MPa at 5 wt% loading with a 1:1 fiber ratio. In contrast, the palm‐rich 2:1 formulation exhibited the highest flexural strength of 97.49 MPa at 15 wt%, representing a 23.2% improvement over neat PP. Impact strength increased with fiber loading, reaching 15.00 kJ/m 2 for the 15 wt% tamarind‐rich formulation. Alkali treatment of the selected 5 wt% palm‐rich 2:1 composite increased tensile, flexural, and impact strengths by 46.3%, 22.9%, and 76.2%, respectively, while reducing water absorption by 41.7%. FTIR and SEM results indicated removal of non‐cellulosic constituents and improved fiber–matrix interaction after treatment. Formulations showed dominant DTG peaks above 465°C.