Reprocessability of PLA through Chain Extension for Fused Filament Fabrication

Abstract

As additive manufacturing (AM) technologies have been gaining popularity in the plastic processing sector, it has become a major concern to establish closed-loop recycling strategies to maximize the value of the materials processed, therefore enhancing their sustainability. However, there are challenges to overcome related to the performance of recycled materials since, after mechanical recycling, the molecular degradation of thermoplastics shifts their performance and processability. In this work, it was hypothesized that the incorporation of a chain extender (CE) during the reprocessing would allow us to overcome these drawbacks. To attest this conjecture, the influence of 1,3-Bis(4,5-dihydro-2-oxazolyl)benzene (PBO), used as a CE, on mechanical, thermal, and rheological properties of polilactic acid (PLA) was studied. Furthermore, a closed-loop recycling system based on Fused Filament Fabrication (FFF) was attempted, consisting of the material preparation, filament extrusion, production of 3D components, and mechanical recycling steps. PBO partially recovered the recycled PLA mechanical performance, reflected by an increase in both tensile modulus (+13%) and tensile strength (+121%), when compared with recycled PLA without PBO. Printability tests were conducted, with the material’s brittle behavior being the major constraint for successfully establishing a closed-loop recycling scheme for FFF applications.

Keywords

• additive manufacturing
• PLA
• plastic recycling
• PLA chain extension
• PBO
• thermo-mechanical degradation