Thermomechanical Properties of Natural Rubber/OPEFB Composites With Hybrid Latex–Starch Coupling Agent

Natural rubber composites remain essential for industrial applications in Indonesia, particularly in tire manufacturing, where improved rigidity and strength are required. This study investigates the use of oil palm empty fruit bunch fiber as a sustainable filler to enhance the thermomechanical properties while promoting agricultural waste valorization. Oil palm empty fruit bunch fiber, abundant and underutilized, was incorporated at 0, 5, 10, and 15 phr (parts per hundred rubber), with a hybrid latex–starch coupling agent (3 phr) synthesized via the glow discharge electrolysis plasma method to improve fiber–rubber interfacial compatibility. Fourier‐transform infrared spectroscopy was used to evaluate chemical interactions, while dynamic mechanical analysis assessed stiffness, damping behavior, and structural stability. Findings show that increased fiber content markedly improved interfacial bonding and thermomechanical performance, with 15 phr achieving optimal balance. This study highlights the dual benefits of performance enhancement and environmental sustainability, supporting the development of high‐value natural rubber composites from renewable resources.