This study aims to optimize the mechanical characteristics of Sisal-polypropylene composites by investigating the impact of varying the compounding factors on these qualities. These parameters include fiber feeding location, barrel temperature, and fiber content. A capillary rheometer was used to track the changes in viscosity of the mixed compounds in relation to shear rate and temperature. Blends were tested at predetermined shear rates using a Couette shear rate theory–based extruder screw speed chart. In order to determine how each processing variable affected the mechanical characteristics of the composites, an analysis of variance (ANOVA) was conducted, and experimental designs were based on Taguchi’s optimization method. The optimization study revealed that, in addition to barrel temperature, the mechanical characteristics of the specimens were highly influenced by fiber content and feeding position inside the extruder. Compounds containing 40 wt % fiber, when treated at 180 ºC and fed into the extruder’s melt zone, had an average modulus value of 7 GPa and a strength value of 48 MPa. The viscosity measurements show minimal variations at shear speeds above 1850 s−1, making it suitable for analyzing these substances. The scanning electron micrographs (SEM) reveal that the fibers were coated uniformly with polymer, and there was some seepage through the core, resulting in twofold shear effect. The optimal screw speeds for the blends studied here ranged from 75 to 220 rpm when using the present extruder (D<inf>o</inf>/Di = 1.3 and shear rates 1850 s− 1 to 4750 s− 1). © 2024 Elsevier B.V., All rights reserved.