Chemical compatibilization of natural <i>Yucca filifera</i> ( <scp>A</scp> sparagaceae) fibers and their effects on the thermal, morphological, and mechanical properties of different molecular weight polypropylene composites

Abstract Delignified Yucca filifera fibers (DYFFs) were made compatible with the saturated fatty acids caproic (FA 6 ), lauric (FA 12 ), and stearic (FA 18 ). This last acted as the most efficient compatibilizer. The optimum fiber/compatibilizer ratio was 1:1 in hexane solution at 80°C. Sulfuric acid (H 2 SO 4 ) was an effective catalyst for the chemical reaction, although it produced oxidized fibers. Therefore, it was appropriate not to catalyze the reaction. Compatibilized FA 18 ‐DYFF had a crystallinity index of 65.1% and a crystal size of 26.6 Å. The polypropylene (PP) matrices were low molecular weight fiber grade (PP35) and high molecular weight injection molding grade (PP11), with fiber saturation limits of 30 and 10 wt%. The electron microscopy micrographs of the compatibilized PP35‐FA 18 DYFF and PP11‐FA 18 DYFF composites indicated fiber incorporation and close polymer‐fiber interactions. The thermogravimetric measurements demonstrated a thermal stability of 250°C and 260°C. The viscosity and shear stress measurements as a function of the shear rate were relatively similar in the PP11 composites. However, they exhibited a sharp transition at the shear rate of 200 s −1 in those of PP35. The corresponding mechanical properties depended on the PP molecular weight and fiber concentration, exhibiting increases in flexural strength, flexural modulus, Shore hardness, and Izod impact. The compatible stable composites can find applications ranging from automotive interiors to packaging. Highlight Chemically compatible fibers of Yucca filifera are reinforcers of polypropylene. Yucca Filifera fibers are compatible with polypropylene through fatty acids. The compatibilization reactions preserve the natural color of the fibers. The saturation of polypropylene matrices depends on their molecular weight. The resultant composites show good thermal stability.