Innovative continuous polypropylene fiber composite filament for material extrusion

Material extrusion is a common additive manufacturing technique used in various fields, including engineering and medicine. Continuous development of innovative feedstock materials for the material-extrusion process is indispensable to broaden the use of this additive manufacturing technique. This work is focused on the development and characterization of a continuous fiber-reinforced thermoplastic composite filament for the material-extrusion process. Continuous polypropylene (PP) fiber is used to reinforce poly(ε-caprolactone) (PCL), a tissue-scaffolding material commonly used in the medical field. Filaments with different fiber contents are produced through a hot melt impregnation process. Thermal analysis is conducted to evaluate the thermal properties of the filament. The mechanical properties of the filaments are evaluated through tensile testing, and the effect of the fiber content on tensile strength and Young’s modulus is determined. It was found that the strength and modulus of PCL increased significantly with continuous PP fibers added. The addition of 9 vol% PP fibers can improve the tensile strength of PCL by more than 600% and its tensile modulus by more than 200%. The printability of the continuous PP fiber-reinforced PCL composite filament was also demonstrated. This study demonstrates the effectiveness of improving the mechanical property of PCL by adding fibers, which offers a promising avenue for the advancement of biocompatible material-extrusion printing materials.