Green Wet Grinding Modification of Coir Fibers: Mechanistic Insights Into Enhanced Tribological Performance of Eco‐Composites

ABSTRACT This study examines the performance of coir fiber as a reinforcement phase in eco‐friendly composites. The fibers were modified via a wet grinding treatment, and three sample groups were prepared: untreated, cyclically wet‐ground for 5 cycles, and cyclically wet‐ground for 10 cycles. The investigation was carried out from two complementary perspectives: the intrinsic properties of the fibers and the macroscopic performance of the resulting composites. Comprehensive characterization—including Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), X‐Ray Diffraction (XRD), and Fourier‐Transform Infrared Spectroscopy (FTIR)—was conducted to assess changes in the surface morphology, thermal stability, crystalline structure, and chemical composition of the coir fibers. In addition, tribological tests were performed to evaluate the coefficient of friction and wear loss of the composites. The results indicate that wet grinding effectively removes surface impurities and optimizes the crystalline structure of coir fibers, thereby improving fiber–matrix interfacial adhesion. These structural enhancements contributed to a significant improvement in the overall mechanical performance of the composites. Specifically, after 10 cycles of wet grinding, the composites exhibited an 85.7% reduction in wear rate and a 45.5% decrease in the coefficient of friction compared to untreated samples, demonstrating superior wear resistance and frictional stability. This work offers valuable insights for expanding the application of coir fibers in sustainable composite materials.