Twin-screw extrusion of short Kevlar fiber–reinforced nylon composite filaments with enhanced mechanical properties and morphology

This paper presents the development and characterization of cost-effective short Kevlar fiber reinforced nylon composite filaments. The effect of Kevlar fiber content on the tensile properties and the fiber distribution morphology was explored. A small amount of short Kevlar fiber was twin-screw compounded with nylon to study the reinforcing effects. Optical microscopy was used to investigate the morphology and the fiber distribution in the nylon matrix. The tensile strength of Kevlar composites increased to 90 MPa and 99 MPa at the fiber content of 1 wt% and 3 wt%, respectively, compared with the tensile strength of 84 MPa for pure nylon. As the fiber content increased from 0 to 3 wt%, the tensile modulus increased from 3.28 to 3.77 GPa. The optical microscopy and SEM images indicate that the twin-screw compounder with a proper screw configuration could disperse and distribute the Kevlar fibers uniformly in the nylon matrix. Statistically, this study demonstrates that the tensile strength and tensile modulus of nylon filament can be effectively enhanced with the addition of small amount of Kevlar fiber (i.e., less than 3 wt%), without sacrificing the ductility.