Research on the miscibility, mechanical properties and printability of polylactic acid/poly (ε-caprolactone) blends: insights from molecular dynamics simulation and experiments

As known, the poor toughness of Polylactic acid (PLA) limits its further application, especially as a bone implant withstanding complex loadings. Blending PLA with Poly (ε-caprolactone) (PCL) under the action of compatibilizers is a proven method to improve the toughness of PLA, while the excess compatibilizers is hard to remove and easy to contaminate the matrix material. This study employed a molecular dynamics simulation combining experimental testing method to investigate the miscibility, mechanical properties and printability of PLA/PCL blends at different compositions without adding any compatibilizers, so as to obtain an ideal PLA/PCL filament for FDM printing bone scaffolds. Results of binding energy distribution and intermolecular interaction show that the miscibility of PLA and PCL is not very good, only the blend of 9PLA/1PCL is miscible. The calculated static mechanical properties and tensile testing results indicate the stiffness or hardness of blends decrease with the addition of PCL, while the toughness firstly increases and then decreases with the introduction of PCL, and the blend of 9PLA/1PCL possesses the best ductility and toughness. Moreover, the results of surface morphology confirm the miscible of 9PLA/1PCL blend and explain why the tensile properties of 9PLA/1PCL is the best, a better miscibility indicating better mechanical properties. Finally, the results of printability indicates that, due to the fluidity of PCL, the printability of blend becomes worse with the increase of PCL content, and the blend of 9PLA/1PCL possesses a relatively good printability. This work provides a practical guidance to the design of PLA/PCL blend filament for FDM printing bone scaffolds. Graphical Abstract