Sustainable Coconut Coir as a Bio‐Filler in Natural Rubber Composites: Influence of Particle Size and Filler Loading
Ing‐orn Sittitanadol, Kornkanok Yodboonma, Thitima Plianklang, Aniwat Hasook, Pranee Chumsamrong, Witawat Singsang, Natkrita PrasoetsophaABSTRACT
In this study, the bio‐filler used for natural rubber (NR) is made from coconut coir (CC). Coconut coir, an abundant agricultural waste in Thailand, was incorporated into NR at different loadings (60, 80, and 100 phr) and particle sizes (180 and 355 μm), and the NR composites were prepared by two‐roll mill and compression molding to examine their effects on curing behavior and properties. The results indicate that NR composites using small CC particles (180 μm) have better dispersion within NR and stronger rubber–filler interactions than those using large ones, leading to improved mechanical properties. This is especially evident when using small CC particles at 100 phr, where optimum results are obtained as tensile strength improves by 297%, Young's modulus by 816%, stiffness by 863%, and compression set by 311% compared to pristine NR. However, elongation at break tends to decrease due to restricted rubber chain mobility. Although high levels of CC particles increase strength, NR composites filled with small CC particles at 60 phr provide a balance of strength, flexibility, hardness, and compression set. The results suggest that CC can be used as a bio‐filler for eco‐friendly NR composites and has potential for speed bump applications.