Improving Interlayer Adhesion of 3D Printed PLA/PCL Blends Using Triblock Copolymers

One of the primary challenges in 3D printing techniques based on layer-by-layer deposition of thermoplastic polymers is the poor mechanical properties of printed parts, due to reduced interlayer adhesion. Our study presents a straightforward method to improve the interlayer adhesion of poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) blends processed using enantiomeric PDLA-PCL-PDLA and PLLA-PCL-PLLA isotactic triblock copolymers as additives during the filament extrusion and 3D printing of a commercial 80/20 w/w PLA/PCL blend. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses revealed improved crystallinity in the PLA-PCL blend containing PDLA-PCL-PDLA triblock copolymer. This improvement in crystallinity directly correlated with the increase in mechanical properties for the PLA/PCL blends containing PDLA-PCL-PDLA in comparison with PLLA-PCL-PLLA, as evident by the tensile strength values of 30–32 MPa and 20–21 MPa, respectively. Furthermore, the PDLA-PCL-PDLA triblock copolymer formed insoluble stereocomplexes that could thermally diffuse through the 3D-printed layers, significantly improving interlayer adhesion. This was evidenced by the 70% reduction in the void area for the PDLA-PCL-PDLA system compared to PLLA-PCL-PLLA and neat PLA/PCL blends, which exhibited average void sizes of 0.8, 1.4, and 2.6 mm², respectively.