Atomic-scale and experimental investigation on the micro-structures and mechanical properties of PLA blending with CMC for additive manufacturing

As one of the most promising biodegradable material, poly(lactic acid) (PLA) is widely used for 3D printing bone scaffolds. However, the inflammation resulted by the intermediate product (lactic acid) of PLA degradation and poor cell affinity still pose a challenge. Blending PLA with o-carboxymethyl chitosan (CMC) is a proven method to achieve a better cell affinity and mechanical behavior material. This study applied a molecular dynamics simulation combining experimental method to investigate the micro-structures and mechanical properties of PLA/CMC composites. Composites were prepared by fused mixing process and extruded into filaments for FDM printing. Results show that the addition of CMC largely reduces the fractional free volume and the molecular chain motion capability, and results a higher density and better hydrophilic system. Interestingly, the tensile modulus increases as the concentration of CMC increases, indicating the introduction of CMC could enhance the stiffness of PLA. While, the tensile strength first increases and then decreases with the increase of CMC content, and 8PLA/2CMC owns the largest tensile strength. Finally, the root reason for these phenomena was found to be attributed to the stronger intermolecular interaction of CMC, the stronger interaction would result the aggregation behavior of CMC.