3D printing-enabled self-assembling β-nucleating agent alignment: Structural evolution and mechanical performances

Achieving good alignment of fillers within the composites is critical towards developing the high performance of the final 3D printed objects. Herein, flow-induced the alignment of self-assembling beta-nucleating agent (SANA(beta)) within the isotactic polypropylene (iPP) matrix was achieved via fused deposition modeling (FDM) process. The influence of printing speed on the alignment of SANA(beta), crystalline structure, and mechanical properties of FDM printed samples were investigated. Due to the converging nozzle effect, SANA(beta) fibers were fragmented from 26.13 mu m to 9.98 mu m in length, generating more oriented templates and further preferentially aligned along the printing direction to trigger the iPP crystallization. As a result, the crystal morphology of the printed sample was transformed from alpha-form to beta-form hybrid shish-kebab structure. Highly oriented beta-crystal was observed in iPP/ SANA beta (FT) samples, as evidenced by 2D-WAXD. 2D-SAXS results revealed the formation of plenty of oriented lamellae in FT samples, which were arranged perpendicular and parallel to the printing direction. The aligned SANA beta also contributed to maintaining a high beta-crystal content to overcome the shortcomings of rapid decrease of beta-crystal for iPP at a high printing speed. Benefiting from this, with the increasing printing speed, compared with elongation at break of iPP samples decreased from 241.36% to 61.32%, those of FT sample increased dramatically from 305.07% to 390.23% but with a slight fade of less than 1% in the tensile strength. Additionally, the as-printed honeycomb array structure of FT sample presented superior energy absorption capacity and thus could function as loading-bear objects, highlighting the advantages of the alignment of self-reinforcing beta-form hybrid shish-kebab.

Automated summary

Achieving good alignment of fillers is crucial for the development of high-performance 3D printed objects. This study investigated the influence of printing speed on the alignment of self-assembling beta-nucleating agent (SANA(beta)) within the isotactic polypropylene (iPP) matrix, as well as the crystalline structure and mechanical properties of the printed samples. The results showed that the alignment of SANA(beta) was enhanced due to the converging nozzle effect, leading to the transformation of the crystal morphology and improved mechanical properties. The aligned SANA(beta) also helped maintain a high beta-crystal content, overcoming the limitations of rapid decrease in beta-crystal for iPP at high printing speeds.