Enhanced Interlayer Adhesion of 3D Printed Poly(lactide acid) with Ultralow Hyperbranched Poly(ester imide)s

The layer-by-layer process of fused deposition modeling (FDM) is well-known for introducing anisotropy in 3D printed parts due to weak interlayer adhesion. Moreover, the existing physical blend modification methods still face the side effects caused by the heavy use of additives, such as high cost, poor biocompatibility and weakening of primary properties. In this study, hyperbranched polymers poly(ester imide)s (HBPEIs) were blended into the poly(lactic acid) (PLA) matrix to enhance the interlayer adhesion of 3D printed parts. The application effect of HBPEIs in different processing modes was discussed. The effect of different amounts of HBPEIs on the mechanical properties of PLA specimens was investigated. Results showed that by adding just 0.1wt% HBPEIs, the maximum tensile strength for samples printed with a 90° raster orientation increased from 23.1 MPa to 46.6 MPa while maintaining an isotropic behavior at around 95.9%. Microstructures, rheological behaviors, and thermal properties of the printed specimens were characterized and compared to understand the underlying enhancement mechanism. It suggested that HBPEIs significantly improved interlayer adhesion by promoting chain diffusion and cold-crystallization between layers. This study showed that using ultralow additives can significantly enhance the interlayer adhesion in FDM parts.