Effects of extrusion parameters on tensile strength of polybenzimidazole fiber-reinforced high density polyethylene composites

The objectives of this study were to examine the effects of fiber content and extrusion parameters on polybenzimidazole (PBI) fiber-reinforced polyethylene composites and to determine the optimum values for the tensile strength. The PBI fiber was physically mixed with high density polyethylene (HDPE) and then extruded through a twin screw extruder. The extrusion parameters were studied at different levels, barrel temperatures at 240°C, 250°C and 260°C and screw speeds at 12 rpm, 15 rpm and 18 rpm. The tensile strength was measured using a universal testing machine. A response surface experimental design using Design-Expert was applied to investigate the effect of fiber loading and extrusion parameters (barrel temperature, screw speed) on tensile properties of the resulting composite and consequently analyzing the optimized value for these parameters to yield maximum tensile strength. The analysis predicted a linear model which suggests that in order to achieve maximum tensile strength the screw speed should be 18 rpm, the barrel temperature at 240°C and at a fiber loading of 2%.