Effect of Screw Speed-Induced Starch Molecular Weight Changes on the Process and Dry Mechanical Properties of 3D-Printed PLA/TPS Stents

This article investigated the effect of screw speed on the molecular weight of starch during thermoplastic starch (TPS) preparation, as well as the effect of this molecular weight on the 3D printing process, interlayer adhesion, molecular orientation, molecular forces, relative crystallinity, and dry mechanical properties of PLA/TPS stents. The increase in screw speed during the preparing of TPS was found to reduce the molecular weight of starch. The reduction in molecular weight of starch was beneficial for the extrusion of filaments and enhanced continuity and uniformity in the lines of 3D-printed stents but reduced the interlayer adhesion of 3D-printed stents. The molecular orientation of stents diminished with decreasing starch molecular weight, leading to a reduction in molecular forces and short-range ordering. This decline was detrimental in terms of enhancing both axial and radial compression characteristics of 3D-printed stents. Considering the influence of starch molecular weight on both the 3D printing process and molecular conformation, the mechanical properties of the 3D-printed PLA/TPS stent were optimized when the screw speed for preparing TPS was set to 160 r/min. The findings will offer theoretical support for the advancement of 3D-printed stents.