Melt-processed poly (L-lactic acid) / cellulose nanocrystals biocomposites for 3D printing: Improved melt processibility and inter-fuse adhesion

Owing to the renewable/biodegradable characters, cellulose nanomaterials have been proposed to modify poly (L-lactic acid) (PLLA) for producing fully green, high performance fused deposition modeling (FDM) consumables. However, to realize the industrial application, the efficient dispersion of hydrophilic cellulose nanofillers in hydrophobic PLLA matrix by industrial melt compounding route rather than solution compounding remains a challenge. Herein, by using polyvinyl acetate (PVAc) modified cellulose nanocrystals (CNCs) powder (CNCs-PVAc) containing mixture of CNCs grafted by PVAc and PVAc homopolymer latex, the homogeneous dispersion of CNCs in PLLA has been achieved by simple melt blend. The results show that the addition of CNCs-PVAc with 5 wt% loading enhances both the melt processibility and inter-fuse adhesion of PLLA remarkably, which in turn results in the improvement of tensile breaking energy by 257%, inter-layer adhesion strength and notched impact toughness by 103% and 57.0%, respectively, as well as good dimensional stability. This work provides an industrial route to prepare PLLA/CNCs-PVAc nanocomposites with high performance for meeting the requirements of strength and dimensional accuracy of FDM parts for end applications.