The effect of eco-friendly chemical treatment on sisal fiber and its epoxy composites: thermal, mechanical, tribological and morphological properties

The purpose of the present work is to assess the effectiveness of a low-cost and environmentally friendly chemical modification of sisal fibers based on the usage of sodium citrate (SC) and stearic acid (SA) on the thermal, mechanical, tribological and morphological characteristics of sisal fiber reinforced epoxy composites (SREC). Scanning electron microscopy (SEM) was used to investigate the morphological properties of the sisal fibers, which demonstrated that the chemical treatment eliminated the contaminants from the fibers' surface. The reduction of hemicellulose and lignin contents of the fiber was confirmed by Fourier transform infrared (FTIR) analysis following both chemical treatments. Thermal stability of the treated fibers showed a slight reduction as revealed by Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). Mechanical properties like tensile, flexural and inter-laminar shear strength showed appreciable improvement for the SA treated SREC (8.05%, 8.50% and 29.42%) and SC treated SREC (23.27%, 13.13% and 51.02%) when compared to untreated SREC. Furthermore, the tribological behaviour of the composites reinforced with treated fibers showed improved wear resistance and frictional properties in comparison to untreated composites. To better understand the fiber/matrix adhesion, morphological examinations of fracture and worn surfaces of composite samples were done using SEM. The test results suggest that the sodium citrate treatment is superior to the stearic acid treatment in improving the composites' mechanical and tribological properties.