Mechanical properties of polypropylene/natural fiber composites: Comparison of wood fiber and cotton fiber

In this study, the mechanical properties of polypropylene (PP)/natural fiber composites were studied. For the natural fiber component of the composites, cotton fiber was compared with wood fiber. The effect of the melt index of PP on the mechanical properties of the composites was also investigated. In order to improve the poor interfacial interaction between the hydrophilic natural fibers and the hydrophobic matrix PP, maleic anhydride (MAH) grafted PP (PP-g-MAH) was used as a compatibilizer. The tensile strength of the PP/wood fiber composites decreases with increasing wt% of the wood fibers, whereas that of the PP/cotton fiber composites displays different behavior. With the addition of 10 wt% cotton fiber, the tensile strength decreases, but with the addition of 20 and 30 wt% cotton fiber it increases because of the entanglement of the cotton fibers. For the PP/wood fiber composites, the melt flow index (MI) of PP was also found to be a key factor governing the mechanical properties (tensile and flexural strengths). The use of PP-g-MAH was helpful to increase the tensile and flexural strengths of the PP/cotton fiber and PP/wood fiber composites, due to the increased interaction between the fiber and PP matrix.