Material behaviourEffects of entrance convergence angle and fiber content on the rheological properties of Pithecellobium clypearia fiber/high-density polyethylene composites

The entrance converging flow method was used to investigate the influences of entrance convergence angle and fiber content on the rheological behavior of Pithecellobium clypearia fiber (PCF)/high-density polyethylene (HDPE) composites. Shear and extensional rheological parameters were also measured. It is found that the extensional action exerted on the materials reaches a maximum at a die angle of 120° at certain plunger rates. Wall slippage occurs easily for PCF/HDPE composites with higher fiber content with a die entry angle of 120°, causing a substantial decrease in the entrance pressure drop of the orifice die. Both shear and extensional non-Newtonian indices of HDPE and PCF/HDPE composites were less than 1, consistent with shear- and tension-thinning rheological behavior. Within the fiber content range used in this study, the shear viscosity increased slightly with fiber content, while the extensional viscosity decreased initially and then increased with increasing fiber content.