Tailored crystalline structure and enhanced impact strength of isotactic polypropylene/high-density polyethylene blend by controlling the printing speed of fused filament fabrication

Fused filament fabrication (FFF) is the most commonly used 3D printing technology. In this work, the isotactic polypropylene/high-density polyethylene blend was used for FFF for the first time. A printing platform with arrays of conical holes was designed to overcome the warpage deformation of product. In order to investigate the influences of shearing force during the nozzle-extrusion process and stretching force during deposition process on the part property, various printing speeds were selected for series of samples. WAXD, SAXS and SEM measurements were used to study the phase morphology and crystalline structure of components. Results reveal that with the increase in printing speed, the PP crystal would deform into shish-kebab structure and PE crystal would deform into epitaxy crystalline structure owing to the strong shearing and stretching forces. These structures improved the impact strength by about 5 times. The printing speed showed slight influence on the thermal behavior. This work confirms the applicability of semicrystalline polymer in FFF technology and gives a deep understanding toward the printing conditions and part property. The obtained results also provide a new method to fabricate high-performance product which will broaden the research field of FFF.