Post-extrusion process for the robust preparation of highly uniform multiphase polymeric 3D printing filaments

Fused filament fabrication 3D printing demands the preparation of polymeric filaments of highly uniform dimensions in order to achieve the best possible mechanical performance. This stringent requirement is a challenging task and becomes even more difficult when multiphase hybrid polymers are used. In this work, a post-extrusion setup is presented, allowing for the preparation of immiscible quaternary polymeric blend filaments of highly stable dimensions. The polymer blend used is bio-based and is comprised of poly(L-lactide), poly(ethylene oxide), poly(ether-b-amide), and polyamide-11. The setup is connected to an extruder die. By incorporating a precisely localized temperature control over a pathway of 66 mm, the extrudate melt is initially transformed into a stable semisolid state. Forced convection cooling, imposed at a distance of 4-5 mm from the last static cooling zone, allows thereafter the complete solidification of the profile. Filaments with a uniform diameter of 1.75 and 2.85 mm are manufactured. The developed approach can be used to manufacture, otherwise non-processable, complex quaternary polymer blend filaments with a highly controlled diameter in the range of 0.1-4.5 mm with no restriction regarding the filament length. The produced filaments were used to 3D print dogbone samples with very high elongation at break.