Raman and FTIR-Based Classification of Microplastics for Sustainable 3D Printing Material Conversion

Abstract
The ubiquity of thermoplastics in FDM 3D printing presents promising opportunities for circular economy projects such as mitigating plastic pollution and microplastic accumulation in marine ecosystems. This work proposes a circular economy process for collecting, characterizing, and recycling microplastic beach cleanup debris into usable 3D printing filament. Microplastics, composed predominantly of degraded Polylactic Acid (PLA), Acrylonitrile Butadiene Styrene (ABS),and polyethylene terephthalate, are cleaned and size- and density-sorted by mechanical separation first. Compositionally heterogeneous, specific identification before reuse is required. Recycling streams are sorted with Raman and Fourier-transform infrared (FTIR) spectroscopy. Non-destructive and yielding a rapid and reliable chemical fingerprint, these techniques allow for high-speed recycling sorting. Sorted thermoplastics are pelletized, dried, and blended with virgin material to stabilize the process. The blend is extruded into FDM-compatible filament, with optimized process conditions to neutralize the impact of degradation and contaminants. The process demonstrates the feasibility of recycling microplastic waste into usable material for additive manufacturing. Synergy between leading-edge spectroscopic analysis and recycling is beneficial to both environmental remediation and green manufacturing. Up-scaling the method and further optimization of the mechanical and printability specifications of recycled filament are the subject of future research. Keywords - Additive manufacturing, FTIR spectroscopy, Raman spectroscopy, Microplastic recycling