Exploring the impact of water soaking on the mechanical, thermal, and physical properties of Paederia foetida fiber stem biocomposites: A study in sustainable material innovation

Biocomposites reinforced with natural fibers have gained significant attention due to their environmental benefits and potential to replace synthetic composites. However, their performance in humid environments remains a concern. This study aims to investigate the mechanical, thermal, and physicochemical properties of Paederia foetida fiber-reinforced biocomposites after water immersion, to better understand their durability under such conditions. The biocomposites were prepared by embedding different volume fractions (2.5 %, 5 %, 10 %, 20 %, and 25 %) of chemically treated Paederia foetida fibers (PFs) into a polyester matrix. The PFs were extracted from stems, treated with 5 % NaOH, washed, and dried before being incorporated into the polyester and molded by hot press. The biocomposite samples were then immersed in water for 72 and 168 hours, with their properties compared to unsoaked controls. The results revealed that the unsoaked biocomposites exhibited good tensile strength, modulus of elasticity, and flexural strength. Despite increasing the fiber content from 2.5 % to 25 % by volume, the density of the biocomposites remained low. After 72 and 168 hours of water immersion, a reduction in tensile strength, modulus of elasticity, and flexural strength was observed, alongside an increase in density, swelling thickness, and water absorption, attributed to water ingress through the fibers and biocomposite cavities. The thermal stability of the biocomposites was minimally affected by water absorption, maintaining strong resistance at temperatures ranging from 400 °C to 800 °C, even after prolonged water exposure.These findings suggest that the developed PFs/polyester biocomposites are a viable alternative material for building applications, offering a balance of mechanical performance and environmental sustainability, with good thermal resistance even in humid conditions.