Citation:

Potter, P., Souhail R. Al-Abed, F. Hasan, AND S. Lomnicki. Influence of polymer additives on gas-phase emissions from 3D printer filaments. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, 279:130543, (2021). https://doi.org/10.1016/j.chemosphere.2021.130543

Impact/Purpose:

Polymers used in 3D printing are known to emit hazardous materials when heated. While the emissions from pristine polymers and some filaments have been studied, many filaments contain additives that may influence their hazardous emissions. For example, carbon nanotubes (CNTs) are added to some filaments to confer structural and electrical properties and are likely to interact with volatile organic compound (VOC) emissions. This research used a commercially-available CNT-containing 3D printer filament to investigate the effect of CNTs on VOC emissions during the printing process. While the presence of CNTs caused a slight overall decrease in the total VOC emissions, there was a shift towards more hazardous compounds being emitted. These findings should influence future studies on 3D printer emissions to include additives such as CNTs, metals, and dyes. These methodologies may be used by EPA's Chemical Safety and Pollution Prevention (OCSPP), Consumer Protection and Safety Commission (CPSC), and National Institute of Occupational of Safety and Health (NIOSH).

Description:

A collection of six commercially available, 3D printer filaments were analyzed with respect to their gas-phase emissions, specifically volatile organic compounds (VOCs), during simulated fused deposition modeling (FDM). Filaments were chosen because they were advertised to contain metal particles or carbon nanotubes. During experimentation, some were found to contain other non-advertised additives that greatly influenced gas-phase emissions. Three polylactic acid (PLA) filaments containing either copper, bronze, or stainless steel particles were studied along in addition to three carbon nanotube (CNT) filaments made from PLA, acrylonitrile-butadiene-styrene (ABS), or polycarbonate (PC). The metal-additive PLA filaments were found to emit primarily lactide, acetaldehyde, and 1-chlorododecane. The polycyclic aromatic hydrocarbon (PAH) naphthalene was also emitted. The presence of metal particles in the PLA caused higher total emissions than any other PLA filament reported in the literature. In addition, the filament with stainless steel particles had a threefold increase in total VOCs compared to the copper and bronze particles. Two of three CNT-containing filaments emitted compounds that have not been reported before for PLA and PC. The discovery of gas-phase emissions related to non-advertised additives was most concerning. The CNT-PLA filament was found to emit high concentrations of silanols and siloxanes, likely due to silanol co-polymers. The CNT-PC filament emitted chlorobenzene, a toxic halogenated aromatic, which was likely formed from unreacted polymerization solvent or reactants. A comparison between certain emitted VOCs and their suggested maximum inhalation limits shows that printing as little as 20 g of certain filaments can subject the user to hazardous concentrations of multiple toxic VOCs with carcinogenic properties (e.g., acetaldehyde, 1,4-dioxane, and bis(2-ethylhexyl) phthalate). The presence of additives that are not advertised by the manufacturer and with unknown inhalation toxicity effects creates a risk that is not known to the user when selecting a 3D printer filament. The use of certain additives, whether advertised or not, should be reevaluated due to their effects on VOC emissions during 3D printing.

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