Demand for natural fibers reinforced composites is growing as an alternative to synthetic fiber reinforced plastic composites. However, poor compatibility between natural fiber and matrix has limited its development. Therefore, it is necessary to improve their interfacial adhesion to improve the comprehensive properties of composites. In this work, sisal fibers were subjected to an alkali/polyvinyl alcohol coating treatment by an ultrasonic impregnation method, and the sisal/high-density polyethylene composite was prepared by a twin-screw extruder. The Fourier transform infrared spectroscopy was used to characterize the modification effect of sisal fiber. The surface morphology of sisal fiber and the interfacial morphology of sisal/high-density polyethylene composites were observed. The mechanical properties and water absorption of sisal/ high-density polyethylene composites were also studied. The results show that alkali/polyvinyl alcohol coating compound treatment can effectively improve the interfacial adhesion between sisal fiber and high-density polyethylene, improve the mechanical properties of composite, and reduce water absorption. Alkali/polyvinyl alcohol coating compound treatment is a very environment-friendly, cost-effective fiber modification method when compared with traditional modification methods. It is helpful for the development and application of natural fibers reinforced composites.
