Closed-loop recycling of polyamide12 powder from selective laser sintering into sustainable composites

A considerable amount of powder residue is generated during the selective laser sintering (SLS) process. Processing the powder residue into filaments for extrusion-based additive manufacturing (EAM) provides an opportunity to recycle SLS residue without significantly reducing its value. In this study, the feasibility of using a milled carbon fiber (mCF)/recycled polyamide12 (rPA12) composite filament for EAM was demonstrated. A microscopic study on the morphology of mCF showed that mCF is a short and smooth fiber. The mCF did not significantly change the melting temperature, crystallization temperature or crystallinity of rPA12 as measured by differential scanning calorimetry (DSC). A morphological study on the fracture-surface of the composites revealed that there was moderate interfacial interaction between the mCF and PA12. Tensile strength, tensile modulus, flexural strength, flexural modulus and impact strength of rPA12 were improved by 35%, 163%, 61%, 138% and 23%, respectively with the addition of 30 wt.% mCF.