Lifting the quality of fused filament fabrication of polylactic acid based composites

The development of well-designed polylactic acid (PLA) based composite filaments through fused filament fabrication (FFF) is crucial, as PLA printed parts are characterized by a high brittleness. Here we focus on FFF composite formation using ductile poly (butylene adipate-co-terephthalate) (PBAT), the nanoclay cloisite and the chain extender Joncryl. A high modulus, flexibility, toughness and notched impact strength result upon combining PLA/PBAT (80:20; mass basis) with a sufficiently high cloisite amount (1-5 phr) supported by a suited Joncryl amount (0.3 phr). A fine PBAT dispersion is then ensured, as confirmed by scanning and transmission electron microscopy. For high cloisite amounts (e.g. 10 phr) the crystallinity and vicat softening temperature enhance but cloisite aggregation is unavoidable, leading to a strong reduction in tensile strain and toughness. Annealing increases crystallinity thus material strength, rigidity and impact, at least partially overruling the need of a fine dispersion. Novel radar charts are also reported to select an optimal bio-based blend suitable for different end-user applications by adjusting the composition and possible post-annealing of printed products.

Automated summary

The study found that a well-designed composite formula can improve the flexibility and strength of PLA printed parts, with PBAT as a diffuser, cloisite as a nanoclay diffuser, and Joncryl as a chain extender playing a key role. At the same time, a high content of cloisite will increase the crystallinity and Vicat softening temperature, but will lead to aggregation, reducing tensile strain and toughness.