Effect of coconut fiber treatment with limestone water media on the fiber surface, wettability, and interface shear strength

The development of technology has increased the need for composite materials, where the technology of composite materials with natural fiber reinforcement is growing. The existence of natural fiber is very abundant, and it has not been fully utilized. Until now, the use of coconut fiber was still limited to the furniture and household handicraft industries. Coconut coir fiber has the potential as a raw material for composite materials. The lack of strength of the bonds is due to the hydrophobic fiber, and the fiber surface is less rough, and dirty. This study evaluates the coir surface characteristic of the fiber and its bounding with the polyester matrix after being treated by limestone water. The scanning electron microscope was used for observing fiber surfaces and surface matrix. The wettability test to observe fiber surface energy was performed. Interface shear strength to evaluate the bonds between fibers and matrix was determined. Coconut coir fibers were immersed in limestone water, with a 5 % percentage of limestone and time variations of 0, 4, 8, 12, 16, and 20 hours. The scanning microscope electron observations of fibers show that the fiber surface tends to be clean, rough, and grooved. The highest surface energy was obtained at 40.74 mN/m during the limestone water immersion for 8 hours. The highest value of the interface shear strength between the fiber and the matrix is 3.80 MPa during 8-hour immersion, 0, 4, 12, 16, and 20-hour immersion, respectively, 3.02, 3.09, 3.52, 3.47, and 4.40 MPa. The results showed that coir fiber with limestone water immersion for 8 hours had a clean, rough, and grooved surface so that the bond between the fiber and matrix was better. This research shows that limestone water can be used as a fiber treatment medium which was natura