Volatile organic compound and particulate emissions from the production and use of thermoplastic biocomposite 3D printing filaments

Biocomposites (BCs) can be used as substitutes for unsustainable polymers in 3D printing, but their safety demands additional investigation as biological fillers may produce altered emissions during thermal processing. Commercial filament extruders can be used to produce custom feedstocks, but they are another source of airborne contaminants and demand further research. These knowledge gaps are targeted in this study. Volatile organic compound (VOC), carbonyl compound, ultrafine particle (UFP), and fine (PM2.5) and coarse (PM10) particle air concentrations were measured in this study as a filament extruder and a 3D printer were operated under an office environment using one PLA and four PLA-based BC feedstocks. Estimates of emission rates (ERs) for total VOCs (TVOC) and UFPs were also calculated. VOCs were analyzed with a GC-MS system, carbonyls were analyzed with an LC-MS/MS system, whereas real-time particle concentrations were monitored with continuously operating instruments. VOC concentrations were low throughout the experiment; TVOC ranged between 34-63 mu g/m(3) during filament extrusion and 41-56 mu g/m(3) during 3D printing, which represent calculated TVOC ERs of 2.6-3.6 x 10(2) and 2.9-3.6 x 10(2) mu g/min. Corresponding cumulative carbonyls ranged between 60-91 and 190-253 mu g/m(3). Lactide and miscellaneous acids and alcohols were the dominant VOCs, while acetone, 2-butanone, and formaldehyde were the dominant carbonyls. Terpenes contributed for ca. 20-40% of TVOC during BC processing. The average UFP levels produced by the filament extruder were 0.85 x 10(2)-1.05 x 10(3) #/cm(3), while the 3D printer generated 6.05 x 10(2)-2.09 x 10(3) #/cm(3) particle levels. Corresponding particle ERs were 5.3 x 10(8)-6.6 x 10(9) and 3.8 x 10(9)-1.3 x 10(10) #/min. PM2.5 and PM10 particles were produced in the following average quantities; PM2.5 levels ranged between 0.2-2.2 mu g/m(3), while PM10 levels were between 5-20 mu g/m(3) for all materials. The main difference between the pure PLA and BC feedstock emissions was terpenes, present during all BC extrusion processes. BCs are similar emission sources as pure plastics based on our findings, and a filament extruder produces contaminants at comparable or slightly lower levels in comparison to 3D printers.

Automated summary

Biocomposites can be used as substitutes for unsustainable polymers in 3D printing, but their safety needs further investigation. This study measured the concentrations of volatile organic compounds, carbonyl compounds, ultrafine particles, and fine and coarse particles in the air during the operation of a filament extruder and a 3D printer using different feedstocks. The study found that the emissions from biocomposites were similar to pure plastics and the filament extruder produced contaminants at comparable or slightly lower levels compared to the 3D printer.