Study of the effect surface treatment of Kenaf fiber on mechanical and water absorption of kenaf filled unsaturated polyester composite

Abstract

In this research, unsaturated polyester/kenaf fiber (UP/KF) composites was prepared by using hand lay-up process. The effect of surface treatment of kenaf fiber on mechanical, morphology, chemical structure and water absorption of kenaf filled unsaturated polyester composites were studied. Different concentrations of stearic acid (SA) were applied, i.e. 0, 0.4, and 0.8 wt%. The Fourier transform infrared (FT-IR) spectra of kenaf fiber shows high intensity of the peak around 3300-3400 cm-1, which is attributed to the hydrogen bonded OH stretching. However, the treated kenaf fiber with stearic acid shows the elimination of OH group and this peak is vanished. This is due to the reaction of (-COOH) group of stearic with (-OH) group of kenaf fiber. Tensile strength of treated kenaf fiber/ unsaturated polyester composites was found to be higher for 40 wt% loading of kenaf fiber. The highest tensile strength value was obtained after treatment with 0.4 wt% concentration of stearic acid at 56 MPa and tensile modulus was at 2409 MPa. From the flexural strength result obtained, it is clearly seen that 40 wt% loading of kenaf fiber and treatment with 0.4 wt% concentration of stearic acid give the highest value at 72 MPa and flexural modulus at 3929 MPa. Scanning Electron Microscope (SEM) observation revealed that the surface of kenaf fiber after treatment with SA became rougher. Moreover, the treatment of kenaf fiber with stearic acid gives better fiber to matrix interaction of kenaf fiber inside the polymeric matrix. The results of water absorption study revealed that increasing the loading of KF in the composite will result is increasing the tendency to absorb water. However, the absorption was significantly decreased after treatment with stearic acid as well as the time to reach to the equilibrium state.