Miaozi Huang, Alois K. Schlarb

• In the present work, microfibrillar composites (MFCs) consisting of polypropylene (PP) and poly(ethylene terephthalate) (PET) were successfully produced by melt extrusion and cold stretching. The resulting filaments were then printed using fused filament fabrication. The morphological results demonstrate that the highly oriented PET fibrils after stretching are still well preserved in the printed components. Since the printing process defines the alignment of the fibrils in the final component the fibers can be perfectly adapted to the load paths. Comparative analyses of the mechanical properties reveal that the PET fibrils act as an effective reinforcement in the 3D printed components, resulting in the superior mechanical performance of the PP/PET MFCs compared to a PP/PET blend and a neat PP. Due to the combination of material and innovative processing, the study opens up a new way of using the morphology-based enormous potential of polymer fibers for lightweight, cost-effective and recyclable full polymer solutions in compact components.