Palmyra Palm Shell (Borassus flabellifer) Properties Part 2: Insights Into Its Thermal and Mechanical Properties

Abstract

Advancements in modern engineering design require materials that maintain thermal and mechanical stability under diverse conditions. To promote sustainability and eco-friendliness, researchers are increasingly exploring natural alternatives to synthetic fibers. Among bio-fibers, Borassus flabellifer fruit shell (husk), has no other uses than disposal or waste-to-energy in Bangladesh. While other parts of the plant, such as, the fruit and leaf stalks, are commonly utilized for fine and coarse fibers, the husk fiber remains underexplored. Hence, this study investigates exclusively the thermal properties of untreated Borassus husk fibers according to ASTM E2550 and ASTM E1269-11 standards and evaluates their curved specimens' mechanical properties using ASTM D2344 and ASTM D6415 standards. The findings reveal that raw Borassus husk fibers exhibit remarkable thermal stability, characterized by a higher char content and an elevated integral process decomposition temperature compared to the its fine and coarse fibers. During cellulose decomposition, the husk fibers demonstrate a specific heat capacity of 1.6 J/g°C, which surpasses that of coconut fibers. Additionally, mechanical testing indicates that the curved husk possesses competitive inter-laminar tensile strength and short-beam strength, comparable to glass fiber-reinforced polymers, curved woven glass/polyester composites and some bio-composites. Fracture surface analysis reveals a unique morphology, featuring non-uniform, cross-linked, and porous tubular structures, which contribute to the material's distinct thermal and mechanical properties. These results highlight the potential of untreated Borassus husk fibers as a viable material for engineering applications. Utilizing this underexplored resource could promote the cultivation and preservation of B. flabellifer trees, thereby encouraging sustainable development.