The effect of chemical surface modification of banana and pineapple fibers on the interfacial adhesion with unsaturated polyester resin composites

The weak fiber/matrix adhesion is the main barrier to employ natural fiber reinforced polymer composites for various applications. This study focuses on improving fiber/matrix adhesion in banana and pineapple fibers using alkaline pretreatment followed by acetylation (A-A). The surface modification of banana and pineapple fibers was studied using bundle fibers tensile test, structural, chemical, infrared spectral and morphological analyzes. Moreover, the mechanical properties and failure mechanisms of untreated and treated composites were studied. The results reveal that the crystallinity index of treated banana and pineapple fibers was increased by 68% and 3.4% compared with untreated banana and pineapple fibers, respectively. Furthermore, low Oxygen/Carbon ratio and smooth surface of treated fibers improved fiber/matrix adhesion with unsaturated polyester resin. At 40 wt.% fiber loading, treated banana composites (TBC) showed significant improvements in tensile strength, flexural strength and hardness by 27.1%, 34.4% and 6.5%, respectively, compared to untreated banana composites (UBC). Similarly, treated pineapple composites (TPC) exhibited enhancements of 13.3%, 13.8% and 8.8%, respectively, over untreated pineapple composites (UPC). Finally, the microstructural analysis of fractured composites showed substantial reduction of fiber/matrix debonding, fiber pullout and fracture in TBC and TPC, which is well correlated with improvements of mechanical properties. This study concludes that A-A treated banana and pineapple fibers composites are promising materials for lightweight structural applications including automotive and aircraft interior panels.