3D printed remendable polylactic acid blends with uniform mechanical strength enabled by a dynamic Diels-Alder reaction

Here we report a 3D printable polymer that retains uniform mechanical strength after printing and can be used with a conventional fused filament fabrication (FFF) printer. To achieve this, a synthetic polymer containing dynamic Diels-Alder functionality was blended with commercially available polylactic acid (PLA). This new polymer contains cross-links that are reversible at the temperatures typically used for FFF 3D printers. By increasing the cross-link density of the polymer system, we were able to dramatically improve both ultimate strength and toughness along the interfilament junctions of the printed material up to similar to 290% and similar to 1150% respectively. The final achieved ultimate strength and toughness values for the optimized system are isotropic within error along the three representative print directions X, Y, and Z. Self-healing studies on the Z print direction of the optimized blend showed a 77% recovery of the ultimate strength vs. control PLA having only a 6% recovery, further proving the advanced interfilamentous adhesion via the fmDA dynamics.